cmd/internal/obj: change Prog.From3 to RestArgs ([]Addr)

This change makes it easier to express instructions
with arbitrary number of operands.

Rationale: previous approach with operand "hiding" does
not scale well, AVX and especially AVX512 have many
instructions with 3+ operands.

x86 asm backend is updated to handle up to 6 explicit operands.
It also fixes issue with 4-th immediate operand type checks.
All `ytab` tables are updated accordingly.

Changes to non-x86 backends only include these patterns:
`p.From3 = X` => `p.SetFrom3(X)`
`p.From3.X = Y` => `p.GetFrom3().X = Y`

Over time, other backends can adapt Prog.RestArgs
and reduce the amount of workarounds.

-- Performance --

x/benchmark/build:

$ benchstat upstream.bench patched.bench
name      old time/op                 new time/op                 delta
Build-48                  21.7s ± 2%                  21.8s ± 2%   ~     (p=0.218 n=10+10)

name      old binary-size             new binary-size             delta
Build-48                  10.3M ± 0%                  10.3M ± 0%   ~     (all equal)

name      old build-time/op           new build-time/op           delta
Build-48                  21.7s ± 2%                  21.8s ± 2%   ~     (p=0.218 n=10+10)

name      old build-peak-RSS-bytes    new build-peak-RSS-bytes    delta
Build-48                  145MB ± 5%                  148MB ± 5%   ~     (p=0.218 n=10+10)

name      old build-user+sys-time/op  new build-user+sys-time/op  delta
Build-48                  21.0s ± 2%                  21.2s ± 2%   ~     (p=0.075 n=10+10)

Microbenchmark shows a slight slowdown.

name        old time/op  new time/op  delta
AMD64asm-4  49.5ms ± 1%  49.9ms ± 1%  +0.67%  (p=0.001 n=23+15)

func BenchmarkAMD64asm(b *testing.B) {
  for i := 0; i < b.N; i++ {
    TestAMD64EndToEnd(nil)
    TestAMD64Encoder(nil)
  }
}

Change-Id: I4f1d37b5c2c966da3f2127705ccac9bff0038183
Reviewed-on: https://go-review.googlesource.com/63490
Run-TryBot: Iskander Sharipov <iskander.sharipov@intel.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

21 files changed, 513 insertions, 481 deletions

diff --git a/src/cmd/asm/internal/arch/amd64.go b/src/cmd/asm/internal/arch/amd64.go
deleted file mode 100644
index ff20d32daa..0000000000
--- a/src/cmd/asm/internal/arch/amd64.go
+++ /dev/null
@@ -1,28 +0,0 @@
-// Copyright 2016 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// This file encapsulates some of the odd characteristics of the
-// AMD64 instruction set, to minimize its interaction
-// with the core of the assembler.
-
-package arch
-
-import (
-	"cmd/internal/obj"
-	"cmd/internal/obj/x86"
-)
-
-// IsAMD4OP reports whether the op (as defined by an amd64.A* constant) is
-// a 4-operand instruction.
-func IsAMD4OP(op obj.As) bool {
-	switch op {
-	case x86.AVPERM2F128,
-		x86.AVPALIGNR,
-		x86.AVPERM2I128,
-		x86.AVINSERTI128,
-		x86.AVPBLENDD:
-		return true
-	}
-	return false
-}
diff --git a/src/cmd/asm/internal/asm/asm.go b/src/cmd/asm/internal/asm/asm.go
index 24aa0537ca..b5e4bddb96 100644
--- a/src/cmd/asm/internal/asm/asm.go
+++ b/src/cmd/asm/internal/asm/asm.go
@@ -384,7 +384,7 @@ func (p *Parser) asmJump(op obj.As, cond string, a []obj.Addr) {
 				prog.Reg = p.getRegister(prog, op, &a[1])
 			} else {
 				// Compare register with immediate and jump.
-				prog.From3 = newAddr(a[1])
+				prog.SetFrom3(a[1])
 			}
 			break
 		}
@@ -567,7 +567,7 @@ func (p *Parser) asmInstruction(op obj.As, cond string, a []obj.Addr) {
 			if arch.IsARMBFX(op) {
 				// a[0] and a[1] must be constants, a[2] must be a register
 				prog.From = a[0]
-				prog.From3 = newAddr(a[1])
+				prog.SetFrom3(a[1])
 				prog.To = a[2]
 				break
 			}
@@ -576,13 +576,8 @@ func (p *Parser) asmInstruction(op obj.As, cond string, a []obj.Addr) {
 			prog.Reg = p.getRegister(prog, op, &a[1])
 			prog.To = a[2]
 		case sys.AMD64:
-			// Catch missing operand here, because we store immediate as part of From3, and can't distinguish
-			// missing operand from legal value 0 in obj/x86/asm6.
-			if arch.IsAMD4OP(op) {
-				p.errorf("4 operands required, but only 3 are provided for %s instruction", op)
-			}
 			prog.From = a[0]
-			prog.From3 = newAddr(a[1])
+			prog.SetFrom3(a[1])
 			prog.To = a[2]
 		case sys.ARM64:
 			// ARM64 instructions with one input and two outputs.
@@ -601,7 +596,7 @@ func (p *Parser) asmInstruction(op obj.As, cond string, a []obj.Addr) {
 			prog.To = a[2]
 		case sys.I386:
 			prog.From = a[0]
-			prog.From3 = newAddr(a[1])
+			prog.SetFrom3(a[1])
 			prog.To = a[2]
 		case sys.PPC64:
 			if arch.IsPPC64CMP(op) {
@@ -623,7 +618,7 @@ func (p *Parser) asmInstruction(op obj.As, cond string, a []obj.Addr) {
 				prog.To = a[2]
 			case obj.TYPE_CONST:
 				prog.From = a[0]
-				prog.From3 = newAddr(a[1])
+				prog.SetFrom3(a[1])
 				prog.To = a[2]
 			default:
 				p.errorf("invalid addressing modes for %s instruction", op)
@@ -634,7 +629,7 @@ func (p *Parser) asmInstruction(op obj.As, cond string, a []obj.Addr) {
 			if a[1].Type == obj.TYPE_REG {
 				prog.Reg = p.getRegister(prog, op, &a[1])
 			} else {
-				prog.From3 = newAddr(a[1])
+				prog.SetFrom3(a[1])
 			}
 			prog.To = a[2]
 		default:
@@ -646,7 +641,7 @@ func (p *Parser) asmInstruction(op obj.As, cond string, a []obj.Addr) {
 			if arch.IsARMBFX(op) {
 				// a[0] and a[1] must be constants, a[2] and a[3] must be registers
 				prog.From = a[0]
-				prog.From3 = newAddr(a[1])
+				prog.SetFrom3(a[1])
 				prog.Reg = p.getRegister(prog, op, &a[2])
 				prog.To = a[3]
 				break
@@ -666,26 +661,15 @@ func (p *Parser) asmInstruction(op obj.As, cond string, a []obj.Addr) {
 			}
 		}
 		if p.arch.Family == sys.AMD64 {
-			// 4 operand instruction have form ymm1, ymm2, ymm3/m256, imm8
-			// So From3 is always just a register, so we store imm8 in Offset field,
-			// to avoid increasing size of Prog.
-			prog.From = a[1]
-			prog.From3 = newAddr(a[2])
-			if a[0].Type != obj.TYPE_CONST {
-				p.errorf("first operand must be an immediate in %s instruction", op)
-			}
-			if prog.From3.Type != obj.TYPE_REG {
-				p.errorf("third operand must be a register in %s instruction", op)
-			}
-			prog.From3.Offset = int64(p.getImmediate(prog, op, &a[0]))
+			prog.From = a[0]
+			prog.RestArgs = []obj.Addr{a[1], a[2]}
 			prog.To = a[3]
-			prog.RegTo2 = -1
 			break
 		}
 		if p.arch.Family == sys.ARM64 {
 			prog.From = a[0]
 			prog.Reg = p.getRegister(prog, op, &a[1])
-			prog.From3 = newAddr(a[2])
+			prog.SetFrom3(a[2])
 			prog.To = a[3]
 			break
 		}
@@ -693,12 +677,12 @@ func (p *Parser) asmInstruction(op obj.As, cond string, a []obj.Addr) {
 			if arch.IsPPC64RLD(op) {
 				prog.From = a[0]
 				prog.Reg = p.getRegister(prog, op, &a[1])
-				prog.From3 = newAddr(a[2])
+				prog.SetFrom3(a[2])
 				prog.To = a[3]
 				break
 			} else if arch.IsPPC64ISEL(op) {
 				// ISEL BC,RB,RA,RT becomes isel rt,ra,rb,bc
-				prog.From3 = newAddr(a[2])                // ra
+				prog.SetFrom3(a[2])                       // ra
 				prog.From = a[0]                          // bc
 				prog.Reg = p.getRegister(prog, op, &a[1]) // rb
 				prog.To = a[3]                            // rt
@@ -712,13 +696,13 @@ func (p *Parser) asmInstruction(op obj.As, cond string, a []obj.Addr) {
 			if a[1].Type == obj.TYPE_REG {
 				prog.From = a[0]
 				prog.Reg = p.getRegister(prog, op, &a[1])
-				prog.From3 = newAddr(a[2])
+				prog.SetFrom3(a[2])
 				prog.To = a[3]
 				break
 			} else if a[1].Type == obj.TYPE_CONST {
 				prog.From = a[0]
 				prog.Reg = p.getRegister(prog, op, &a[2])
-				prog.From3 = newAddr(a[1])
+				prog.SetFrom3(a[1])
 				prog.To = a[3]
 				break
 			} else {
@@ -733,7 +717,7 @@ func (p *Parser) asmInstruction(op obj.As, cond string, a []obj.Addr) {
 			}
 			prog.From = a[0]
 			prog.Reg = p.getRegister(prog, op, &a[1])
-			prog.From3 = newAddr(a[2])
+			prog.SetFrom3(a[2])
 			prog.To = a[3]
 			break
 		}
@@ -752,10 +736,10 @@ func (p *Parser) asmInstruction(op obj.As, cond string, a []obj.Addr) {
 			} else {
 				mask = (^uint32(0) >> uint(mask2+1)) & (^uint32(0) << uint(31-(mask1-1)))
 			}
-			prog.From3 = &obj.Addr{
+			prog.SetFrom3(obj.Addr{
 				Type:   obj.TYPE_CONST,
 				Offset: int64(mask),
-			}
+			})
 			prog.To = a[4]
 			break
 		}
diff --git a/src/cmd/compile/internal/arm64/ssa.go b/src/cmd/compile/internal/arm64/ssa.go
index 24a8fb83a4..e74207b856 100644
--- a/src/cmd/compile/internal/arm64/ssa.go
+++ b/src/cmd/compile/internal/arm64/ssa.go
@@ -571,7 +571,7 @@ func ssaGenValue(s *gc.SSAGenState, v *ssa.Value) {
 		p.From.Type = obj.TYPE_REG // assembler encodes conditional bits in Reg
 		p.From.Reg = arm64.COND_LO
 		p.Reg = v.Args[0].Reg()
-		p.From3 = &obj.Addr{Type: obj.TYPE_REG, Reg: r1}
+		p.SetFrom3(obj.Addr{Type: obj.TYPE_REG, Reg: r1})
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = v.Reg()
 	case ssa.OpARM64DUFFZERO:
diff --git a/src/cmd/compile/internal/ppc64/ssa.go b/src/cmd/compile/internal/ppc64/ssa.go
index c56f53c206..330d58becf 100644
--- a/src/cmd/compile/internal/ppc64/ssa.go
+++ b/src/cmd/compile/internal/ppc64/ssa.go
@@ -124,7 +124,7 @@ func ssaGenISEL(s *gc.SSAGenState, v *ssa.Value, cr int64, r1, r2 int16) {
 	p.To.Type = obj.TYPE_REG
 	p.To.Reg = r
 	p.Reg = r1
-	p.From3 = &obj.Addr{Type: obj.TYPE_REG, Reg: r2}
+	p.SetFrom3(obj.Addr{Type: obj.TYPE_REG, Reg: r2})
 	p.From.Type = obj.TYPE_CONST
 	p.From.Offset = cr
 }
@@ -551,9 +551,7 @@ func ssaGenValue(s *gc.SSAGenState, v *ssa.Value) {
 		p.From.Type = obj.TYPE_REG
 		p.From.Reg = r1
 		p.Reg = r3
-		p.From3 = new(obj.Addr)
-		p.From3.Type = obj.TYPE_REG
-		p.From3.Reg = r2
+		p.SetFrom3(obj.Addr{Type: obj.TYPE_REG, Reg: r2})
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = r
 
diff --git a/src/cmd/compile/internal/s390x/ssa.go b/src/cmd/compile/internal/s390x/ssa.go
index 8722345a09..6e637487cd 100644
--- a/src/cmd/compile/internal/s390x/ssa.go
+++ b/src/cmd/compile/internal/s390x/ssa.go
@@ -534,10 +534,11 @@ func ssaGenValue(s *gc.SSAGenState, v *ssa.Value) {
 		p := s.Prog(s390x.AMVC)
 		p.From.Type = obj.TYPE_CONST
 		p.From.Offset = vo.Val()
-		p.From3 = new(obj.Addr)
-		p.From3.Type = obj.TYPE_MEM
-		p.From3.Reg = v.Args[1].Reg()
-		p.From3.Offset = vo.Off()
+		p.SetFrom3(obj.Addr{
+			Type:   obj.TYPE_MEM,
+			Reg:    v.Args[1].Reg(),
+			Offset: vo.Off(),
+		})
 		p.To.Type = obj.TYPE_MEM
 		p.To.Reg = v.Args[0].Reg()
 		p.To.Offset = vo.Off()
@@ -570,9 +571,7 @@ func ssaGenValue(s *gc.SSAGenState, v *ssa.Value) {
 		mvc := s.Prog(s390x.AMVC)
 		mvc.From.Type = obj.TYPE_CONST
 		mvc.From.Offset = 256
-		mvc.From3 = new(obj.Addr)
-		mvc.From3.Type = obj.TYPE_MEM
-		mvc.From3.Reg = v.Args[1].Reg()
+		mvc.SetFrom3(obj.Addr{Type: obj.TYPE_MEM, Reg: v.Args[1].Reg()})
 		mvc.To.Type = obj.TYPE_MEM
 		mvc.To.Reg = v.Args[0].Reg()
 
@@ -599,9 +598,7 @@ func ssaGenValue(s *gc.SSAGenState, v *ssa.Value) {
 			mvc := s.Prog(s390x.AMVC)
 			mvc.From.Type = obj.TYPE_CONST
 			mvc.From.Offset = v.AuxInt
-			mvc.From3 = new(obj.Addr)
-			mvc.From3.Type = obj.TYPE_MEM
-			mvc.From3.Reg = v.Args[1].Reg()
+			mvc.SetFrom3(obj.Addr{Type: obj.TYPE_MEM, Reg: v.Args[1].Reg()})
 			mvc.To.Type = obj.TYPE_MEM
 			mvc.To.Reg = v.Args[0].Reg()
 		}
diff --git a/src/cmd/internal/obj/arm/asm5.go b/src/cmd/internal/obj/arm/asm5.go
index 98b45feb60..479005f294 100644
--- a/src/cmd/internal/obj/arm/asm5.go
+++ b/src/cmd/internal/obj/arm/asm5.go
@@ -2068,11 +2068,11 @@ func (c *ctxt5) asmout(p *obj.Prog, o *Optab, out []uint32) {
 		if r == 0 {
 			r = rt
 		}
-		if p.From3 == nil || p.From3.Type != obj.TYPE_CONST {
+		if p.GetFrom3() == nil || p.GetFrom3().Type != obj.TYPE_CONST {
 			c.ctxt.Diag("%v: missing or wrong LSB", p)
 			break
 		}
-		lsb := p.From3.Offset
+		lsb := p.GetFrom3().Offset
 		width := p.From.Offset
 		if lsb < 0 || lsb > 31 || width <= 0 || (lsb+width) > 31 {
 			c.ctxt.Diag("%v: wrong width or LSB", p)
@@ -3310,8 +3310,8 @@ func (c *ctxt5) chipfloat5(e float64) int {
 func nocache(p *obj.Prog) {
 	p.Optab = 0
 	p.From.Class = 0
-	if p.From3 != nil {
-		p.From3.Class = 0
+	if p.GetFrom3() != nil {
+		p.GetFrom3().Class = 0
 	}
 	p.To.Class = 0
 }
diff --git a/src/cmd/internal/obj/arm/obj5.go b/src/cmd/internal/obj/arm/obj5.go
index 32c4643166..59f044ec9d 100644
--- a/src/cmd/internal/obj/arm/obj5.go
+++ b/src/cmd/internal/obj/arm/obj5.go
@@ -186,7 +186,7 @@ func (c *ctxt5) rewriteToUseGot(p *obj.Prog) {
 			p.From.Offset = 0
 		}
 	}
-	if p.From3 != nil && p.From3.Name == obj.NAME_EXTERN {
+	if p.GetFrom3() != nil && p.GetFrom3().Name == obj.NAME_EXTERN {
 		c.ctxt.Diag("don't know how to handle %v with -dynlink", p)
 	}
 	var source *obj.Addr
diff --git a/src/cmd/internal/obj/arm64/asm7.go b/src/cmd/internal/obj/arm64/asm7.go
index ddd43485f7..10f0303785 100644
--- a/src/cmd/internal/obj/arm64/asm7.go
+++ b/src/cmd/internal/obj/arm64/asm7.go
@@ -2331,7 +2331,7 @@ func (c *ctxt7) asmout(p *obj.Prog, o *Optab, out []uint32) {
 		var r int
 		var ra int
 		if p.From3Type() == obj.TYPE_REG {
-			r = int(p.From3.Reg)
+			r = int(p.GetFrom3().Reg)
 			ra = int(p.Reg)
 			if ra == 0 {
 				ra = REGZERO
@@ -2393,7 +2393,7 @@ func (c *ctxt7) asmout(p *obj.Prog, o *Optab, out []uint32) {
 
 				cond ^= 1
 			} else {
-				rf = int(p.From3.Reg) /* CSEL */
+				rf = int(p.GetFrom3().Reg) /* CSEL */
 			}
 		} else {
 			/* CSET */
@@ -2418,12 +2418,12 @@ func (c *ctxt7) asmout(p *obj.Prog, o *Optab, out []uint32) {
 			cond -= COND_EQ
 		}
 		var rf int
-		if p.From3.Type == obj.TYPE_REG {
+		if p.GetFrom3().Type == obj.TYPE_REG {
 			o1 = c.oprrr(p, p.As)
-			rf = int(p.From3.Reg) /* Rm */
+			rf = int(p.GetFrom3().Reg) /* Rm */
 		} else {
 			o1 = c.opirr(p, p.As)
-			rf = int(p.From3.Offset & 0x1F)
+			rf = int(p.GetFrom3().Offset & 0x1F)
 		}
 
 		o1 |= (uint32(rf&31) << 16) | (uint32(cond&15) << 12) | (uint32(p.Reg&31) << 5) | uint32(nzcv)
@@ -2767,12 +2767,12 @@ func (c *ctxt7) asmout(p *obj.Prog, o *Optab, out []uint32) {
 		o1 = c.op0(p, p.As)
 
 	case 42: /* bfm R,r,s,R */
-		o1 = c.opbfm(p, p.As, int(p.From.Offset), int(p.From3.Offset), int(p.Reg), int(p.To.Reg))
+		o1 = c.opbfm(p, p.As, int(p.From.Offset), int(p.GetFrom3().Offset), int(p.Reg), int(p.To.Reg))
 
 	case 43: /* bfm aliases */
 		r := int(p.From.Offset)
 
-		s := int(p.From3.Offset)
+		s := int(p.GetFrom3().Offset)
 		rf := int(p.Reg)
 		rt := int(p.To.Reg)
 		if rf == 0 {
@@ -2821,7 +2821,7 @@ func (c *ctxt7) asmout(p *obj.Prog, o *Optab, out []uint32) {
 		}
 
 	case 44: /* extr $b, Rn, Rm, Rd */
-		o1 = c.opextr(p, p.As, int32(p.From.Offset), int(p.From3.Reg), int(p.Reg), int(p.To.Reg))
+		o1 = c.opextr(p, p.As, int32(p.From.Offset), int(p.GetFrom3().Reg), int(p.Reg), int(p.To.Reg))
 
 	case 45: /* sxt/uxt[bhw] R,R; movT R,R -> sxtT R,R */
 		rf := int(p.From.Reg)
@@ -2977,11 +2977,11 @@ func (c *ctxt7) asmout(p *obj.Prog, o *Optab, out []uint32) {
 			c.ctxt.Diag("implausible condition\n%v", p)
 		}
 		rf := int(p.Reg)
-		if p.From3 == nil || p.From3.Reg < REG_F0 || p.From3.Reg > REG_F31 {
+		if p.GetFrom3() == nil || p.GetFrom3().Reg < REG_F0 || p.GetFrom3().Reg > REG_F31 {
 			c.ctxt.Diag("illegal FCCMP\n%v", p)
 			break
 		}
-		rt := int(p.From3.Reg)
+		rt := int(p.GetFrom3().Reg)
 		o1 |= uint32(rf&31)<<16 | uint32(cond&15)<<12 | uint32(rt&31)<<5 | uint32(nzcv)
 
 	case 58: /* ldar/ldxr/ldaxr */
diff --git a/src/cmd/internal/obj/arm64/obj7.go b/src/cmd/internal/obj/arm64/obj7.go
index b1cf7cdd9f..7f22aa88bb 100644
--- a/src/cmd/internal/obj/arm64/obj7.go
+++ b/src/cmd/internal/obj/arm64/obj7.go
@@ -382,7 +382,7 @@ func (c *ctxt7) rewriteToUseGot(p *obj.Prog) {
 			p.From.Offset = 0
 		}
 	}
-	if p.From3 != nil && p.From3.Name == obj.NAME_EXTERN {
+	if p.GetFrom3() != nil && p.GetFrom3().Name == obj.NAME_EXTERN {
 		c.ctxt.Diag("don't know how to handle %v with -dynlink", p)
 	}
 	var source *obj.Addr
diff --git a/src/cmd/internal/obj/go.go b/src/cmd/internal/obj/go.go
index f0b2c46e4f..dbe9b406dd 100644
--- a/src/cmd/internal/obj/go.go
+++ b/src/cmd/internal/obj/go.go
@@ -10,7 +10,7 @@ func Nopout(p *Prog) {
 	p.As = ANOP
 	p.Scond = 0
 	p.From = Addr{}
-	p.From3 = nil
+	p.RestArgs = nil
 	p.Reg = 0
 	p.To = Addr{}
 }
diff --git a/src/cmd/internal/obj/link.go b/src/cmd/internal/obj/link.go
index 68e1b70ac0..abd90e34d2 100644
--- a/src/cmd/internal/obj/link.go
+++ b/src/cmd/internal/obj/link.go
@@ -209,14 +209,19 @@ const (
 //
 // The general instruction form is:
 //
-//	As.Scond From, Reg, From3, To, RegTo2
+//	(1) As.Scond From [, ...RestArgs], To
+//	(2) As.Scond From, Reg [, ...RestArgs], To, RegTo2
 //
 // where As is an opcode and the others are arguments:
-// From, Reg, From3 are sources, and To, RegTo2 are destinations.
+// From, Reg are sources, and To, RegTo2 are destinations.
+// RestArgs can hold additional sources and destinations.
 // Usually, not all arguments are present.
 // For example, MOVL R1, R2 encodes using only As=MOVL, From=R1, To=R2.
 // The Scond field holds additional condition bits for systems (like arm)
 // that have generalized conditional execution.
+// (2) form is present for compatibility with older code,
+// to avoid too much changes in a single swing.
+// (1) scheme is enough to express any kind of operand combination.
 //
 // Jump instructions use the Pcond field to point to the target instruction,
 // which must be in the same linked list as the jump instruction.
@@ -232,35 +237,62 @@ const (
 // The other fields not yet mentioned are for use by the back ends and should
 // be left zeroed by creators of Prog lists.
 type Prog struct {
-	Ctxt   *Link    // linker context
-	Link   *Prog    // next Prog in linked list
-	From   Addr     // first source operand
-	From3  *Addr    // third source operand (second is Reg below)
-	To     Addr     // destination operand (second is RegTo2 below)
-	Pcond  *Prog    // target of conditional jump
-	Forwd  *Prog    // for x86 back end
-	Rel    *Prog    // for x86, arm back ends
-	Pc     int64    // for back ends or assembler: virtual or actual program counter, depending on phase
-	Pos    src.XPos // source position of this instruction
-	Spadj  int32    // effect of instruction on stack pointer (increment or decrement amount)
-	As     As       // assembler opcode
-	Reg    int16    // 2nd source operand
-	RegTo2 int16    // 2nd destination operand
-	Mark   uint16   // bitmask of arch-specific items
-	Optab  uint16   // arch-specific opcode index
-	Scond  uint8    // condition bits for conditional instruction (e.g., on ARM)
-	Back   uint8    // for x86 back end: backwards branch state
-	Ft     uint8    // for x86 back end: type index of Prog.From
-	Tt     uint8    // for x86 back end: type index of Prog.To
-	Isize  uint8    // for x86 back end: size of the instruction in bytes
+	Ctxt     *Link    // linker context
+	Link     *Prog    // next Prog in linked list
+	From     Addr     // first source operand
+	RestArgs []Addr   // can pack any operands that not fit into {Prog.From, Prog.To}
+	To       Addr     // destination operand (second is RegTo2 below)
+	Pcond    *Prog    // target of conditional jump
+	Forwd    *Prog    // for x86 back end
+	Rel      *Prog    // for x86, arm back ends
+	Pc       int64    // for back ends or assembler: virtual or actual program counter, depending on phase
+	Pos      src.XPos // source position of this instruction
+	Spadj    int32    // effect of instruction on stack pointer (increment or decrement amount)
+	As       As       // assembler opcode
+	Reg      int16    // 2nd source operand
+	RegTo2   int16    // 2nd destination operand
+	Mark     uint16   // bitmask of arch-specific items
+	Optab    uint16   // arch-specific opcode index
+	Scond    uint8    // condition bits for conditional instruction (e.g., on ARM)
+	Back     uint8    // for x86 back end: backwards branch state
+	Ft       uint8    // for x86 back end: type index of Prog.From
+	Tt       uint8    // for x86 back end: type index of Prog.To
+	Isize    uint8    // for x86 back end: size of the instruction in bytes
 }
 
-// From3Type returns From3.Type, or TYPE_NONE when From3 is nil.
+// From3Type returns p.GetFrom3().Type, or TYPE_NONE when
+// p.GetFrom3() returns nil.
+//
+// Deprecated: for the same reasons as Prog.GetFrom3.
 func (p *Prog) From3Type() AddrType {
-	if p.From3 == nil {
+	if p.RestArgs == nil {
 		return TYPE_NONE
 	}
-	return p.From3.Type
+	return p.RestArgs[0].Type
+}
+
+// GetFrom3 returns second source operand (the first is Prog.From).
+// In combination with Prog.From and Prog.To it makes common 3 operand
+// case easier to use.
+//
+// Should be used only when RestArgs is set with SetFrom3.
+//
+// Deprecated: better use RestArgs directly or define backend-specific getters.
+// Introduced to simplify transition to []Addr.
+// Usage of this is discouraged due to fragility and lack of guarantees.
+func (p *Prog) GetFrom3() *Addr {
+	if p.RestArgs == nil {
+		return nil
+	}
+	return &p.RestArgs[0]
+}
+
+// SetFrom3 assigns []Addr{a} to p.RestArgs.
+// In pair with Prog.GetFrom3 it can help in emulation of Prog.From3.
+//
+// Deprecated: for the same reasons as Prog.GetFrom3.
+func (p *Prog) SetFrom3(a Addr) {
+	p.RestArgs = []Addr{a}
 }
 
 // An As denotes an assembler opcode.
diff --git a/src/cmd/internal/obj/pass.go b/src/cmd/internal/obj/pass.go
index 7cc187d01f..edfc3acf79 100644
--- a/src/cmd/internal/obj/pass.go
+++ b/src/cmd/internal/obj/pass.go
@@ -124,8 +124,8 @@ func linkpatch(ctxt *Link, sym *LSym, newprog ProgAlloc) {
 
 	for p := sym.Func.Text; p != nil; p = p.Link {
 		checkaddr(ctxt, p, &p.From)
-		if p.From3 != nil {
-			checkaddr(ctxt, p, p.From3)
+		if p.GetFrom3() != nil {
+			checkaddr(ctxt, p, p.GetFrom3())
 		}
 		checkaddr(ctxt, p, &p.To)
 
diff --git a/src/cmd/internal/obj/ppc64/asm9.go b/src/cmd/internal/obj/ppc64/asm9.go
index dd6429fd0b..2f7e3237b4 100644
--- a/src/cmd/internal/obj/ppc64/asm9.go
+++ b/src/cmd/internal/obj/ppc64/asm9.go
@@ -900,11 +900,11 @@ func (c *ctxt9) oplook(p *obj.Prog) *Optab {
 
 	a1--
 	a3 := C_NONE + 1
-	if p.From3 != nil {
-		a3 = int(p.From3.Class)
+	if p.GetFrom3() != nil {
+		a3 = int(p.GetFrom3().Class)
 		if a3 == 0 {
-			a3 = c.aclass(p.From3) + 1
-			p.From3.Class = int8(a3)
+			a3 = c.aclass(p.GetFrom3()) + 1
+			p.GetFrom3().Class = int8(a3)
 		}
 	}
 
@@ -2461,7 +2461,7 @@ func (c *ctxt9) asmout(p *obj.Prog, o *Optab, out []uint32) {
 		if r == 0 {
 			r = int(p.To.Reg)
 		}
-		d := c.vregoff(p.From3)
+		d := c.vregoff(p.GetFrom3())
 		var a int
 		switch p.As {
 
@@ -2714,7 +2714,7 @@ func (c *ctxt9) asmout(p *obj.Prog, o *Optab, out []uint32) {
 		o2 = AOP_IRR(OP_ADDI, uint32(p.To.Reg), REGTMP, uint32(v))
 
 	case 27: /* subc ra,$simm,rd => subfic rd,ra,$simm */
-		v := c.regoff(p.From3)
+		v := c.regoff(p.GetFrom3())
 
 		r := int(p.From.Reg)
 		o1 = AOP_IRR(c.opirr(p.As), uint32(p.To.Reg), uint32(r), uint32(v))
@@ -2723,7 +2723,7 @@ func (c *ctxt9) asmout(p *obj.Prog, o *Optab, out []uint32) {
 		if p.To.Reg == REGTMP || p.From.Reg == REGTMP {
 			c.ctxt.Diag("can't synthesize large constant\n%v", p)
 		}
-		v := c.regoff(p.From3)
+		v := c.regoff(p.GetFrom3())
 		o1 = AOP_IRR(OP_ADDIS, REGTMP, REGZERO, uint32(v)>>16)
 		o2 = LOP_IRR(OP_ORI, REGTMP, REGTMP, uint32(v))
 		o3 = AOP_RRR(c.oprrr(p.As), uint32(p.To.Reg), uint32(p.From.Reg), REGTMP)
@@ -2736,7 +2736,7 @@ func (c *ctxt9) asmout(p *obj.Prog, o *Optab, out []uint32) {
 	case 29: /* rldic[lr]? $sh,s,$mask,a -- left, right, plain give different masks */
 		v := c.regoff(&p.From)
 
-		d := c.vregoff(p.From3)
+		d := c.vregoff(p.GetFrom3())
 		var mask [2]uint8
 		c.maskgen64(p, mask[:], uint64(d))
 		var a int
@@ -2776,7 +2776,7 @@ func (c *ctxt9) asmout(p *obj.Prog, o *Optab, out []uint32) {
 	case 30: /* rldimi $sh,s,$mask,a */
 		v := c.regoff(&p.From)
 
-		d := c.vregoff(p.From3)
+		d := c.vregoff(p.GetFrom3())
 
 		// Original opcodes had mask operands which had to be converted to a shift count as expected by
 		// the ppc64 asm.
@@ -2847,7 +2847,7 @@ func (c *ctxt9) asmout(p *obj.Prog, o *Optab, out []uint32) {
 		o1 = AOP_RRR(c.oprrr(p.As), uint32(p.To.Reg), 0, uint32(r))
 
 	case 34: /* FMADDx fra,frb,frc,frt (t=a*c±b) */
-		o1 = AOP_RRR(c.oprrr(p.As), uint32(p.To.Reg), uint32(p.From.Reg), uint32(p.Reg)) | (uint32(p.From3.Reg)&31)<<6
+		o1 = AOP_RRR(c.oprrr(p.As), uint32(p.To.Reg), uint32(p.From.Reg), uint32(p.Reg)) | (uint32(p.GetFrom3().Reg)&31)<<6
 
 	case 35: /* mov r,lext/lauto/loreg ==> cau $(v>>16),sb,r'; store o(r') */
 		v := c.regoff(&p.To)
@@ -2889,10 +2889,10 @@ func (c *ctxt9) asmout(p *obj.Prog, o *Optab, out []uint32) {
 		o1 = uint32(c.regoff(&p.From))
 
 	case 41: /* stswi */
-		o1 = AOP_RRR(c.opirr(p.As), uint32(p.From.Reg), uint32(p.To.Reg), 0) | (uint32(c.regoff(p.From3))&0x7F)<<11
+		o1 = AOP_RRR(c.opirr(p.As), uint32(p.From.Reg), uint32(p.To.Reg), 0) | (uint32(c.regoff(p.GetFrom3()))&0x7F)<<11
 
 	case 42: /* lswi */
-		o1 = AOP_RRR(c.opirr(p.As), uint32(p.To.Reg), uint32(p.From.Reg), 0) | (uint32(c.regoff(p.From3))&0x7F)<<11
+		o1 = AOP_RRR(c.opirr(p.As), uint32(p.To.Reg), uint32(p.From.Reg), 0) | (uint32(c.regoff(p.GetFrom3()))&0x7F)<<11
 
 	case 43: /* unary indexed source: dcbf (b); dcbf (a+b) */
 		o1 = AOP_RRR(c.oprrr(p.As), 0, uint32(p.From.Index), uint32(p.From.Reg))
@@ -3062,13 +3062,13 @@ func (c *ctxt9) asmout(p *obj.Prog, o *Optab, out []uint32) {
 		v := c.regoff(&p.From)
 
 		var mask [2]uint8
-		c.maskgen(p, mask[:], uint32(c.regoff(p.From3)))
+		c.maskgen(p, mask[:], uint32(c.regoff(p.GetFrom3())))
 		o1 = AOP_RRR(c.opirr(p.As), uint32(p.Reg), uint32(p.To.Reg), uint32(v))
 		o1 |= (uint32(mask[0])&31)<<6 | (uint32(mask[1])&31)<<1
 
 	case 63: /* rlwmi b,s,$mask,a */
 		var mask [2]uint8
-		c.maskgen(p, mask[:], uint32(c.regoff(p.From3)))
+		c.maskgen(p, mask[:], uint32(c.regoff(p.GetFrom3())))
 
 		o1 = AOP_RRR(c.opirr(p.As), uint32(p.Reg), uint32(p.To.Reg), uint32(p.From.Reg))
 		o1 |= (uint32(mask[0])&31)<<6 | (uint32(mask[1])&31)<<1
@@ -3076,7 +3076,7 @@ func (c *ctxt9) asmout(p *obj.Prog, o *Optab, out []uint32) {
 	case 64: /* mtfsf fr[, $m] {,fpcsr} */
 		var v int32
 		if p.From3Type() != obj.TYPE_NONE {
-			v = c.regoff(p.From3) & 255
+			v = c.regoff(p.GetFrom3()) & 255
 		} else {
 			v = 255
 		}
@@ -3131,7 +3131,7 @@ func (c *ctxt9) asmout(p *obj.Prog, o *Optab, out []uint32) {
 			if p.To.Reg != 0 {
 				c.ctxt.Diag("can't use both mask and CR(n)\n%v", p)
 			}
-			v = c.regoff(p.From3) & 0xff
+			v = c.regoff(p.GetFrom3()) & 0xff
 		} else {
 			if p.To.Reg == 0 {
 				v = 0xff /* CR */
@@ -3270,7 +3270,7 @@ func (c *ctxt9) asmout(p *obj.Prog, o *Optab, out []uint32) {
 			/* imm imm reg reg */
 			/* operand order: SIX, VRA, ST, VRT */
 			six := int(c.regoff(&p.From))
-			st := int(c.regoff(p.From3))
+			st := int(c.regoff(p.GetFrom3()))
 			o1 = AOP_IIRR(c.opiirr(p.As), uint32(p.To.Reg), uint32(p.Reg), uint32(st), uint32(six))
 		} else if p.From3Type() == obj.TYPE_NONE && p.Reg != 0 {
 			/* imm reg reg */
@@ -3288,19 +3288,19 @@ func (c *ctxt9) asmout(p *obj.Prog, o *Optab, out []uint32) {
 		if p.From.Type == obj.TYPE_REG {
 			/* reg reg reg reg */
 			/* 4-register operand order: VRA, VRB, VRC, VRT */
-			o1 = AOP_RRRR(c.oprrr(p.As), uint32(p.To.Reg), uint32(p.From.Reg), uint32(p.Reg), uint32(p.From3.Reg))
+			o1 = AOP_RRRR(c.oprrr(p.As), uint32(p.To.Reg), uint32(p.From.Reg), uint32(p.Reg), uint32(p.GetFrom3().Reg))
 		} else if p.From.Type == obj.TYPE_CONST {
 			/* imm reg reg reg */
 			/* operand order: SHB, VRA, VRB, VRT */
 			shb := int(c.regoff(&p.From))
-			o1 = AOP_IRRR(c.opirrr(p.As), uint32(p.To.Reg), uint32(p.Reg), uint32(p.From3.Reg), uint32(shb))
+			o1 = AOP_IRRR(c.opirrr(p.As), uint32(p.To.Reg), uint32(p.Reg), uint32(p.GetFrom3().Reg), uint32(shb))
 		}
 
 	case 84: // ISEL BC,RA,RB,RT -> isel rt,ra,rb,bc
 		bc := c.vregoff(&p.From)
 
 		// rt = To.Reg, ra = p.Reg, rb = p.From3.Reg
-		o1 = AOP_ISEL(OP_ISEL, uint32(p.To.Reg), uint32(p.Reg), uint32(p.From3.Reg), uint32(bc))
+		o1 = AOP_ISEL(OP_ISEL, uint32(p.To.Reg), uint32(p.Reg), uint32(p.GetFrom3().Reg), uint32(bc))
 
 	case 85: /* vector instructions, VX-form */
 		/* reg none reg */
@@ -3348,7 +3348,7 @@ func (c *ctxt9) asmout(p *obj.Prog, o *Optab, out []uint32) {
 	case 89: /* VSX instructions, XX2-form */
 		/* reg none reg OR reg imm reg */
 		/* 2-register operand order: XB, XT or XB, UIM, XT*/
-		uim := int(c.regoff(p.From3))
+		uim := int(c.regoff(p.GetFrom3()))
 		o1 = AOP_XX2(c.oprrr(p.As), uint32(p.To.Reg), uint32(uim), uint32(p.From.Reg))
 
 	case 90: /* VSX instructions, XX3-form */
@@ -3359,14 +3359,14 @@ func (c *ctxt9) asmout(p *obj.Prog, o *Optab, out []uint32) {
 		} else if p.From3Type() == obj.TYPE_CONST {
 			/* reg reg reg imm */
 			/* operand order: XA, XB, DM, XT */
-			dm := int(c.regoff(p.From3))
+			dm := int(c.regoff(p.GetFrom3()))
 			o1 = AOP_XX3I(c.oprrr(p.As), uint32(p.To.Reg), uint32(p.From.Reg), uint32(p.Reg), uint32(dm))
 		}
 
 	case 91: /* VSX instructions, XX4-form */
 		/* reg reg reg reg */
 		/* 3-register operand order: XA, XB, XC, XT */
-		o1 = AOP_XX4(c.oprrr(p.As), uint32(p.To.Reg), uint32(p.From.Reg), uint32(p.Reg), uint32(p.From3.Reg))
+		o1 = AOP_XX4(c.oprrr(p.As), uint32(p.To.Reg), uint32(p.From.Reg), uint32(p.Reg), uint32(p.GetFrom3().Reg))
 
 	case 92: /* X-form instructions, 3-operands */
 		if p.To.Type == obj.TYPE_CONST {
@@ -3384,7 +3384,7 @@ func (c *ctxt9) asmout(p *obj.Prog, o *Optab, out []uint32) {
 		} else if p.From3Type() == obj.TYPE_CONST {
 			/* reg reg imm */
 			/* operand order: RB, L, RA */
-			l := int(c.regoff(p.From3))
+			l := int(c.regoff(p.GetFrom3()))
 			o1 = AOP_RRR(c.opirr(p.As), uint32(l), uint32(p.To.Reg), uint32(p.From.Reg))
 		} else if p.To.Type == obj.TYPE_REG {
 			cr := int32(p.To.Reg)
@@ -3425,7 +3425,7 @@ func (c *ctxt9) asmout(p *obj.Prog, o *Optab, out []uint32) {
 	case 94: /* Z23-form instructions, 4-operands */
 		/* reg reg reg imm */
 		/* operand order: RA, RB, CY, RT */
-		cy := int(c.regoff(p.From3))
+		cy := int(c.regoff(p.GetFrom3()))
 		o1 = AOP_Z23I(c.oprrr(p.As), uint32(p.To.Reg), uint32(p.From.Reg), uint32(p.Reg), uint32(cy))
 	}
 
diff --git a/src/cmd/internal/obj/ppc64/obj9.go b/src/cmd/internal/obj/ppc64/obj9.go
index b1509e3813..c50cd3b06c 100644
--- a/src/cmd/internal/obj/ppc64/obj9.go
+++ b/src/cmd/internal/obj/ppc64/obj9.go
@@ -176,7 +176,7 @@ func (c *ctxt9) rewriteToUseGot(p *obj.Prog) {
 			p.From.Offset = 0
 		}
 	}
-	if p.From3 != nil && p.From3.Name == obj.NAME_EXTERN {
+	if p.GetFrom3() != nil && p.GetFrom3().Name == obj.NAME_EXTERN {
 		c.ctxt.Diag("don't know how to handle %v with -dynlink", p)
 	}
 	var source *obj.Addr
diff --git a/src/cmd/internal/obj/s390x/asmz.go b/src/cmd/internal/obj/s390x/asmz.go
index 6d2b870f0a..e108032c5c 100644
--- a/src/cmd/internal/obj/s390x/asmz.go
+++ b/src/cmd/internal/obj/s390x/asmz.go
@@ -654,11 +654,11 @@ func (c *ctxtz) oplook(p *obj.Prog) *Optab {
 
 	a1--
 	a3 := C_NONE + 1
-	if p.From3 != nil {
-		a3 = int(p.From3.Class)
+	if p.GetFrom3() != nil {
+		a3 = int(p.GetFrom3().Class)
 		if a3 == 0 {
-			a3 = c.aclass(p.From3) + 1
-			p.From3.Class = int8(a3)
+			a3 = c.aclass(p.GetFrom3()) + 1
+			p.GetFrom3().Class = int8(a3)
 		}
 	}
 
@@ -3534,11 +3534,11 @@ func (c *ctxtz) asmout(p *obj.Prog, asm *[]byte) {
 		if l < 1 || l > 256 {
 			c.ctxt.Diag("number of bytes (%v) not in range [1,256]", l)
 		}
-		if p.From3.Index != 0 || p.To.Index != 0 {
+		if p.GetFrom3().Index != 0 || p.To.Index != 0 {
 			c.ctxt.Diag("cannot use index reg")
 		}
 		b1 := p.To.Reg
-		b2 := p.From3.Reg
+		b2 := p.GetFrom3().Reg
 		if b1 == 0 {
 			b1 = o.param
 		}
@@ -3546,7 +3546,7 @@ func (c *ctxtz) asmout(p *obj.Prog, asm *[]byte) {
 			b2 = o.param
 		}
 		d1 := c.regoff(&p.To)
-		d2 := c.regoff(p.From3)
+		d2 := c.regoff(p.GetFrom3())
 		if d1 < 0 || d1 >= DISP12 {
 			if b2 == REGTMP {
 				c.ctxt.Diag("REGTMP conflict")
@@ -3688,10 +3688,10 @@ func (c *ctxtz) asmout(p *obj.Prog, asm *[]byte) {
 		}
 		mask := c.branchMask(p)
 		if int32(int16(v)) != v {
-			zRIL(_a, opcode2, uint32(p.From.Reg), uint32(c.regoff(p.From3)), asm)
+			zRIL(_a, opcode2, uint32(p.From.Reg), uint32(c.regoff(p.GetFrom3())), asm)
 			zRIL(_c, op_BRCL, mask, uint32(v-sizeRIL/2), asm)
 		} else {
-			zRIE(_c, opcode, uint32(p.From.Reg), mask, uint32(v), 0, 0, 0, uint32(c.regoff(p.From3)), asm)
+			zRIE(_c, opcode, uint32(p.From.Reg), mask, uint32(v), 0, 0, 0, uint32(c.regoff(p.GetFrom3())), asm)
 		}
 
 	case 93: // GOT lookup
@@ -3893,9 +3893,9 @@ func (c *ctxtz) asmout(p *obj.Prog, asm *[]byte) {
 	case 101: // VRX LOAD
 		op, m3, _ := vop(p.As)
 		src := &p.From
-		if p.From3 != nil {
+		if p.GetFrom3() != nil {
 			m3 = uint32(c.vregoff(&p.From))
-			src = p.From3
+			src = p.GetFrom3()
 		}
 		b2 := src.Reg
 		if b2 == 0 {
@@ -3917,12 +3917,12 @@ func (c *ctxtz) asmout(p *obj.Prog, asm *[]byte) {
 	case 103: // VRV GATHER
 		op, _, _ := vop(p.As)
 		m3 := uint32(c.vregoff(&p.From))
-		b2 := p.From3.Reg
+		b2 := p.GetFrom3().Reg
 		if b2 == 0 {
 			b2 = o.param
 		}
-		d2 := uint32(c.vregoff(p.From3))
-		zVRV(op, uint32(p.To.Reg), uint32(p.From3.Index), uint32(b2), d2, m3, asm)
+		d2 := uint32(c.vregoff(p.GetFrom3()))
+		zVRV(op, uint32(p.To.Reg), uint32(p.GetFrom3().Index), uint32(b2), d2, m3, asm)
 
 	case 104: // VRS SHIFT/ROTATE and LOAD GR FROM VR ELEMENT
 		op, m4, _ := vop(p.As)
@@ -3962,8 +3962,8 @@ func (c *ctxtz) asmout(p *obj.Prog, asm *[]byte) {
 
 	case 108: // VRS LOAD WITH LENGTH
 		op, _, _ := vop(p.As)
-		offset := uint32(c.vregoff(p.From3))
-		reg := p.From3.Reg
+		offset := uint32(c.vregoff(p.GetFrom3()))
+		reg := p.GetFrom3().Reg
 		if reg == 0 {
 			reg = o.param
 		}
@@ -3972,9 +3972,9 @@ func (c *ctxtz) asmout(p *obj.Prog, asm *[]byte) {
 	case 109: // VRI-a
 		op, m3, _ := vop(p.As)
 		i2 := uint32(c.vregoff(&p.From))
-		if p.From3 != nil {
+		if p.GetFrom3() != nil {
 			m3 = uint32(c.vregoff(&p.From))
-			i2 = uint32(c.vregoff(p.From3))
+			i2 = uint32(c.vregoff(p.GetFrom3()))
 		}
 		switch p.As {
 		case AVZERO:
@@ -3987,7 +3987,7 @@ func (c *ctxtz) asmout(p *obj.Prog, asm *[]byte) {
 	case 110:
 		op, m4, _ := vop(p.As)
 		i2 := uint32(c.vregoff(&p.From))
-		i3 := uint32(c.vregoff(p.From3))
+		i3 := uint32(c.vregoff(p.GetFrom3()))
 		zVRIb(op, uint32(p.To.Reg), i2, i3, m4, asm)
 
 	case 111:
@@ -3998,7 +3998,7 @@ func (c *ctxtz) asmout(p *obj.Prog, asm *[]byte) {
 	case 112:
 		op, m5, _ := vop(p.As)
 		i4 := uint32(c.vregoff(&p.From))
-		zVRId(op, uint32(p.To.Reg), uint32(p.Reg), uint32(p.From3.Reg), i4, m5, asm)
+		zVRId(op, uint32(p.To.Reg), uint32(p.Reg), uint32(p.GetFrom3().Reg), i4, m5, asm)
 
 	case 113:
 		op, m4, _ := vop(p.As)
@@ -4044,7 +4044,7 @@ func (c *ctxtz) asmout(p *obj.Prog, asm *[]byte) {
 		v1 := uint32(p.To.Reg)
 		v2 := uint32(p.From.Reg)
 		v3 := uint32(p.Reg)
-		v4 := uint32(p.From3.Reg)
+		v4 := uint32(p.GetFrom3().Reg)
 		zVRRd(op, v1, v2, v3, m6, m5, v4, asm)
 
 	case 121: // VRR-e
@@ -4053,7 +4053,7 @@ func (c *ctxtz) asmout(p *obj.Prog, asm *[]byte) {
 		v1 := uint32(p.To.Reg)
 		v2 := uint32(p.From.Reg)
 		v3 := uint32(p.Reg)
-		v4 := uint32(p.From3.Reg)
+		v4 := uint32(p.GetFrom3().Reg)
 		zVRRe(op, v1, v2, v3, m6, m5, v4, asm)
 
 	case 122: // VRR-f LOAD VRS FROM GRS DISJOINT
@@ -4063,7 +4063,7 @@ func (c *ctxtz) asmout(p *obj.Prog, asm *[]byte) {
 	case 123: // VPDI $m4, V2, V3, V1
 		op, _, _ := vop(p.As)
 		m4 := c.regoff(&p.From)
-		zVRRc(op, uint32(p.To.Reg), uint32(p.Reg), uint32(p.From3.Reg), 0, 0, uint32(m4), asm)
+		zVRRc(op, uint32(p.To.Reg), uint32(p.Reg), uint32(p.GetFrom3().Reg), 0, 0, uint32(m4), asm)
 	}
 }
 
diff --git a/src/cmd/internal/obj/s390x/objz.go b/src/cmd/internal/obj/s390x/objz.go
index 3d3571a461..bf4dfd49d5 100644
--- a/src/cmd/internal/obj/s390x/objz.go
+++ b/src/cmd/internal/obj/s390x/objz.go
@@ -140,7 +140,7 @@ func (c *ctxtz) rewriteToUseGot(p *obj.Prog) {
 			p.From.Offset = 0
 		}
 	}
-	if p.From3 != nil && p.From3.Name == obj.NAME_EXTERN {
+	if p.GetFrom3() != nil && p.GetFrom3().Name == obj.NAME_EXTERN {
 		c.ctxt.Diag("don't know how to handle %v with -dynlink", p)
 	}
 	var source *obj.Addr
diff --git a/src/cmd/internal/obj/sizeof_test.go b/src/cmd/internal/obj/sizeof_test.go
index 601e9e2ea6..e70d174637 100644
--- a/src/cmd/internal/obj/sizeof_test.go
+++ b/src/cmd/internal/obj/sizeof_test.go
@@ -24,7 +24,7 @@ func TestSizeof(t *testing.T) {
 	}{
 		{Addr{}, 32, 48},
 		{LSym{}, 56, 104},
-		{Prog{}, 124, 184},
+		{Prog{}, 132, 200},
 	}
 
 	for _, tt := range tests {
diff --git a/src/cmd/internal/obj/util.go b/src/cmd/internal/obj/util.go
index 9bcdbbd127..bf2d209d7f 100644
--- a/src/cmd/internal/obj/util.go
+++ b/src/cmd/internal/obj/util.go
@@ -83,11 +83,7 @@ func (p *Prog) String() string {
 
 	fmt.Fprintf(&buf, "%.5d (%v)\t%v%s", p.Pc, p.Line(), p.As, sc)
 	sep := "\t"
-	quadOpAmd64 := p.RegTo2 == -1
-	if quadOpAmd64 {
-		fmt.Fprintf(&buf, "%s$%d", sep, p.From3.Offset)
-		sep = ", "
-	}
+
 	if p.From.Type != TYPE_NONE {
 		fmt.Fprintf(&buf, "%s%v", sep, Dconv(p, &p.From))
 		sep = ", "
@@ -97,14 +93,11 @@ func (p *Prog) String() string {
 		fmt.Fprintf(&buf, "%s%v", sep, Rconv(int(p.Reg)))
 		sep = ", "
 	}
-	if p.From3Type() != TYPE_NONE {
-		if quadOpAmd64 {
-			fmt.Fprintf(&buf, "%s%v", sep, Rconv(int(p.From3.Reg)))
-		} else {
-			fmt.Fprintf(&buf, "%s%v", sep, Dconv(p, p.From3))
-		}
+	for i := range p.RestArgs {
+		fmt.Fprintf(&buf, "%s%v", sep, Dconv(p, &p.RestArgs[i]))
 		sep = ", "
 	}
+
 	if p.As == ATEXT {
 		// If there are attributes, print them. Otherwise, skip the comma.
 		// In short, print one of these two:
@@ -119,7 +112,7 @@ func (p *Prog) String() string {
 	if p.To.Type != TYPE_NONE {
 		fmt.Fprintf(&buf, "%s%v", sep, Dconv(p, &p.To))
 	}
-	if p.RegTo2 != REG_NONE && !quadOpAmd64 {
+	if p.RegTo2 != REG_NONE {
 		fmt.Fprintf(&buf, "%s%v", sep, Rconv(int(p.RegTo2)))
 	}
 	return buf.String()
diff --git a/src/cmd/internal/obj/x86/asm6.go b/src/cmd/internal/obj/x86/asm6.go
index f636d312d4..86c85c1a6f 100644
--- a/src/cmd/internal/obj/x86/asm6.go
+++ b/src/cmd/internal/obj/x86/asm6.go
@@ -72,14 +72,6 @@ type Optab struct {
 	op     [23]uint8
 }
 
-type ytab struct {
-	from    uint8
-	from3   uint8
-	to      uint8
-	zcase   uint8
-	zoffset uint8
-}
-
 type Movtab struct {
 	as   obj.As
 	ft   uint8
@@ -323,414 +315,418 @@ var reg [MAXREG]int
 var regrex [MAXREG + 1]int
 
 var ynone = []ytab{
-	{Ynone, Ynone, Ynone, Zlit, 1},
+	{Zlit, 1, argList{}},
 }
 
 var ytext = []ytab{
-	{Ymb, Ynone, Ytextsize, Zpseudo, 0},
-	{Ymb, Yi32, Ytextsize, Zpseudo, 1},
+	{Zpseudo, 0, argList{Ymb, Ytextsize}},
+	{Zpseudo, 1, argList{Ymb, Yi32, Ytextsize}},
 }
 
 var ynop = []ytab{
-	{Ynone, Ynone, Ynone, Zpseudo, 0},
-	{Ynone, Ynone, Yiauto, Zpseudo, 0},
-	{Ynone, Ynone, Yml, Zpseudo, 0},
-	{Ynone, Ynone, Yrf, Zpseudo, 0},
-	{Ynone, Ynone, Yxr, Zpseudo, 0},
-	{Yiauto, Ynone, Ynone, Zpseudo, 0},
-	{Yml, Ynone, Ynone, Zpseudo, 0},
-	{Yrf, Ynone, Ynone, Zpseudo, 0},
-	{Yxr, Ynone, Ynone, Zpseudo, 1},
+	{Zpseudo, 0, argList{}},
+	{Zpseudo, 0, argList{Yiauto}},
+	{Zpseudo, 0, argList{Yml}},
+	{Zpseudo, 0, argList{Yrf}},
+	{Zpseudo, 0, argList{Yxr}},
+	{Zpseudo, 0, argList{Yiauto}},
+	{Zpseudo, 0, argList{Yml}},
+	{Zpseudo, 0, argList{Yrf}},
+	{Zpseudo, 1, argList{Yxr}},
 }
 
 var yfuncdata = []ytab{
-	{Yi32, Ynone, Ym, Zpseudo, 0},
+	{Zpseudo, 0, argList{Yi32, Ym}},
 }
 
 var ypcdata = []ytab{
-	{Yi32, Ynone, Yi32, Zpseudo, 0},
+	{Zpseudo, 0, argList{Yi32, Yi32}},
 }
 
 var yxorb = []ytab{
-	{Yi32, Ynone, Yal, Zib_, 1},
-	{Yi32, Ynone, Ymb, Zibo_m, 2},
-	{Yrb, Ynone, Ymb, Zr_m, 1},
-	{Ymb, Ynone, Yrb, Zm_r, 1},
+	{Zib_, 1, argList{Yi32, Yal}},
+	{Zibo_m, 2, argList{Yi32, Ymb}},
+	{Zr_m, 1, argList{Yrb, Ymb}},
+	{Zm_r, 1, argList{Ymb, Yrb}},
 }
 
 var yaddl = []ytab{
-	{Yi8, Ynone, Yml, Zibo_m, 2},
-	{Yi32, Ynone, Yax, Zil_, 1},
-	{Yi32, Ynone, Yml, Zilo_m, 2},
-	{Yrl, Ynone, Yml, Zr_m, 1},
-	{Yml, Ynone, Yrl, Zm_r, 1},
+	{Zibo_m, 2, argList{Yi8, Yml}},
+	{Zil_, 1, argList{Yi32, Yax}},
+	{Zilo_m, 2, argList{Yi32, Yml}},
+	{Zr_m, 1, argList{Yrl, Yml}},
+	{Zm_r, 1, argList{Yml, Yrl}},
 }
 
 var yincl = []ytab{
-	{Ynone, Ynone, Yrl, Z_rp, 1},
-	{Ynone, Ynone, Yml, Zo_m, 2},
+	{Z_rp, 1, argList{Yrl}},
+	{Zo_m, 2, argList{Yml}},
 }
 
 var yincq = []ytab{
-	{Ynone, Ynone, Yml, Zo_m, 2},
+	{Zo_m, 2, argList{Yml}},
 }
 
 var ycmpb = []ytab{
-	{Yal, Ynone, Yi32, Z_ib, 1},
-	{Ymb, Ynone, Yi32, Zm_ibo, 2},
-	{Ymb, Ynone, Yrb, Zm_r, 1},
-	{Yrb, Ynone, Ymb, Zr_m, 1},
+	{Z_ib, 1, argList{Yal, Yi32}},
+	{Zm_ibo, 2, argList{Ymb, Yi32}},
+	{Zm_r, 1, argList{Ymb, Yrb}},
+	{Zr_m, 1, argList{Yrb, Ymb}},
 }
 
 var ycmpl = []ytab{
-	{Yml, Ynone, Yi8, Zm_ibo, 2},
-	{Yax, Ynone, Yi32, Z_il, 1},
-	{Yml, Ynone, Yi32, Zm_ilo, 2},
-	{Yml, Ynone, Yrl, Zm_r, 1},
-	{Yrl, Ynone, Yml, Zr_m, 1},
+	{Zm_ibo, 2, argList{Yml, Yi8}},
+	{Z_il, 1, argList{Yax, Yi32}},
+	{Zm_ilo, 2, argList{Yml, Yi32}},
+	{Zm_r, 1, argList{Yml, Yrl}},
+	{Zr_m, 1, argList{Yrl, Yml}},
 }
 
 var yshb = []ytab{
-	{Yi1, Ynone, Ymb, Zo_m, 2},
-	{Yu8, Ynone, Ymb, Zibo_m, 2},
-	{Ycx, Ynone, Ymb, Zo_m, 2},
+	{Zo_m, 2, argList{Yi1, Ymb}},
+	{Zibo_m, 2, argList{Yu8, Ymb}},
+	{Zo_m, 2, argList{Ycx, Ymb}},
 }
 
 var yshl = []ytab{
-	{Yi1, Ynone, Yml, Zo_m, 2},
-	{Yu8, Ynone, Yml, Zibo_m, 2},
-	{Ycl, Ynone, Yml, Zo_m, 2},
-	{Ycx, Ynone, Yml, Zo_m, 2},
+	{Zo_m, 2, argList{Yi1, Yml}},
+	{Zibo_m, 2, argList{Yu8, Yml}},
+	{Zo_m, 2, argList{Ycl, Yml}},
+	{Zo_m, 2, argList{Ycx, Yml}},
 }
 
 var ytestl = []ytab{
-	{Yi32, Ynone, Yax, Zil_, 1},
-	{Yi32, Ynone, Yml, Zilo_m, 2},
-	{Yrl, Ynone, Yml, Zr_m, 1},
-	{Yml, Ynone, Yrl, Zm_r, 1},
+	{Zil_, 1, argList{Yi32, Yax}},
+	{Zilo_m, 2, argList{Yi32, Yml}},
+	{Zr_m, 1, argList{Yrl, Yml}},
+	{Zm_r, 1, argList{Yml, Yrl}},
 }
 
 var ymovb = []ytab{
-	{Yrb, Ynone, Ymb, Zr_m, 1},
-	{Ymb, Ynone, Yrb, Zm_r, 1},
-	{Yi32, Ynone, Yrb, Zib_rp, 1},
-	{Yi32, Ynone, Ymb, Zibo_m, 2},
+	{Zr_m, 1, argList{Yrb, Ymb}},
+	{Zm_r, 1, argList{Ymb, Yrb}},
+	{Zib_rp, 1, argList{Yi32, Yrb}},
+	{Zibo_m, 2, argList{Yi32, Ymb}},
 }
 
 var ybtl = []ytab{
-	{Yi8, Ynone, Yml, Zibo_m, 2},
-	{Yrl, Ynone, Yml, Zr_m, 1},
+	{Zibo_m, 2, argList{Yi8, Yml}},
+	{Zr_m, 1, argList{Yrl, Yml}},
 }
 
 var ymovw = []ytab{
-	{Yrl, Ynone, Yml, Zr_m, 1},
-	{Yml, Ynone, Yrl, Zm_r, 1},
-	{Yi0, Ynone, Yrl, Zclr, 1},
-	{Yi32, Ynone, Yrl, Zil_rp, 1},
-	{Yi32, Ynone, Yml, Zilo_m, 2},
-	{Yiauto, Ynone, Yrl, Zaut_r, 2},
+	{Zr_m, 1, argList{Yrl, Yml}},
+	{Zm_r, 1, argList{Yml, Yrl}},
+	{Zclr, 1, argList{Yi0, Yrl}},
+	{Zil_rp, 1, argList{Yi32, Yrl}},
+	{Zilo_m, 2, argList{Yi32, Yml}},
+	{Zaut_r, 2, argList{Yiauto, Yrl}},
 }
 
 var ymovl = []ytab{
-	{Yrl, Ynone, Yml, Zr_m, 1},
-	{Yml, Ynone, Yrl, Zm_r, 1},
-	{Yi0, Ynone, Yrl, Zclr, 1},
-	{Yi32, Ynone, Yrl, Zil_rp, 1},
-	{Yi32, Ynone, Yml, Zilo_m, 2},
-	{Yml, Ynone, Ymr, Zm_r_xm, 1}, // MMX MOVD
-	{Ymr, Ynone, Yml, Zr_m_xm, 1}, // MMX MOVD
-	{Yml, Ynone, Yxr, Zm_r_xm, 2}, // XMM MOVD (32 bit)
-	{Yxr, Ynone, Yml, Zr_m_xm, 2}, // XMM MOVD (32 bit)
-	{Yiauto, Ynone, Yrl, Zaut_r, 2},
+	{Zr_m, 1, argList{Yrl, Yml}},
+	{Zm_r, 1, argList{Yml, Yrl}},
+	{Zclr, 1, argList{Yi0, Yrl}},
+	{Zil_rp, 1, argList{Yi32, Yrl}},
+	{Zilo_m, 2, argList{Yi32, Yml}},
+	{Zm_r_xm, 1, argList{Yml, Ymr}}, // MMX MOVD
+	{Zr_m_xm, 1, argList{Ymr, Yml}}, // MMX MOVD
+	{Zm_r_xm, 2, argList{Yml, Yxr}}, // XMM MOVD (32 bit)
+	{Zr_m_xm, 2, argList{Yxr, Yml}}, // XMM MOVD (32 bit)
+	{Zaut_r, 2, argList{Yiauto, Yrl}},
 }
 
 var yret = []ytab{
-	{Ynone, Ynone, Ynone, Zo_iw, 1},
-	{Yi32, Ynone, Ynone, Zo_iw, 1},
+	{Zo_iw, 1, argList{}},
+	{Zo_iw, 1, argList{Yi32}},
 }
 
 var ymovq = []ytab{
 	// valid in 32-bit mode
-	{Ym, Ynone, Ymr, Zm_r_xm_nr, 1},  // 0x6f MMX MOVQ (shorter encoding)
-	{Ymr, Ynone, Ym, Zr_m_xm_nr, 1},  // 0x7f MMX MOVQ
-	{Yxr, Ynone, Ymr, Zm_r_xm_nr, 2}, // Pf2, 0xd6 MOVDQ2Q
-	{Yxm, Ynone, Yxr, Zm_r_xm_nr, 2}, // Pf3, 0x7e MOVQ xmm1/m64 -> xmm2
-	{Yxr, Ynone, Yxm, Zr_m_xm_nr, 2}, // Pe, 0xd6 MOVQ xmm1 -> xmm2/m64
+	{Zm_r_xm_nr, 1, argList{Ym, Ymr}},  // 0x6f MMX MOVQ (shorter encoding)
+	{Zr_m_xm_nr, 1, argList{Ymr, Ym}},  // 0x7f MMX MOVQ
+	{Zm_r_xm_nr, 2, argList{Yxr, Ymr}}, // Pf2, 0xd6 MOVDQ2Q
+	{Zm_r_xm_nr, 2, argList{Yxm, Yxr}}, // Pf3, 0x7e MOVQ xmm1/m64 -> xmm2
+	{Zr_m_xm_nr, 2, argList{Yxr, Yxm}}, // Pe, 0xd6 MOVQ xmm1 -> xmm2/m64
 
 	// valid only in 64-bit mode, usually with 64-bit prefix
-	{Yrl, Ynone, Yml, Zr_m, 1},      // 0x89
-	{Yml, Ynone, Yrl, Zm_r, 1},      // 0x8b
-	{Yi0, Ynone, Yrl, Zclr, 1},      // 0x31
-	{Ys32, Ynone, Yrl, Zilo_m, 2},   // 32 bit signed 0xc7,(0)
-	{Yi64, Ynone, Yrl, Ziq_rp, 1},   // 0xb8 -- 32/64 bit immediate
-	{Yi32, Ynone, Yml, Zilo_m, 2},   // 0xc7,(0)
-	{Ymm, Ynone, Ymr, Zm_r_xm, 1},   // 0x6e MMX MOVD
-	{Ymr, Ynone, Ymm, Zr_m_xm, 1},   // 0x7e MMX MOVD
-	{Yml, Ynone, Yxr, Zm_r_xm, 2},   // Pe, 0x6e MOVD xmm load
-	{Yxr, Ynone, Yml, Zr_m_xm, 2},   // Pe, 0x7e MOVD xmm store
-	{Yiauto, Ynone, Yrl, Zaut_r, 1}, // 0 built-in LEAQ
+	{Zr_m, 1, argList{Yrl, Yml}},      // 0x89
+	{Zm_r, 1, argList{Yml, Yrl}},      // 0x8b
+	{Zclr, 1, argList{Yi0, Yrl}},      // 0x31
+	{Zilo_m, 2, argList{Ys32, Yrl}},   // 32 bit signed 0xc7,(0)
+	{Ziq_rp, 1, argList{Yi64, Yrl}},   // 0xb8 -- 32/64 bit immediate
+	{Zilo_m, 2, argList{Yi32, Yml}},   // 0xc7,(0)
+	{Zm_r_xm, 1, argList{Ymm, Ymr}},   // 0x6e MMX MOVD
+	{Zr_m_xm, 1, argList{Ymr, Ymm}},   // 0x7e MMX MOVD
+	{Zm_r_xm, 2, argList{Yml, Yxr}},   // Pe, 0x6e MOVD xmm load
+	{Zr_m_xm, 2, argList{Yxr, Yml}},   // Pe, 0x7e MOVD xmm store
+	{Zaut_r, 1, argList{Yiauto, Yrl}}, // 0 built-in LEAQ
 }
 
 var ym_rl = []ytab{
-	{Ym, Ynone, Yrl, Zm_r, 1},
+	{Zm_r, 1, argList{Ym, Yrl}},
 }
 
 var yrl_m = []ytab{
-	{Yrl, Ynone, Ym, Zr_m, 1},
+	{Zr_m, 1, argList{Yrl, Ym}},
 }
 
 var ymb_rl = []ytab{
-	{Ymb, Ynone, Yrl, Zmb_r, 1},
+	{Zmb_r, 1, argList{Ymb, Yrl}},
 }
 
 var yml_rl = []ytab{
-	{Yml, Ynone, Yrl, Zm_r, 1},
+	{Zm_r, 1, argList{Yml, Yrl}},
 }
 
 var yrl_ml = []ytab{
-	{Yrl, Ynone, Yml, Zr_m, 1},
+	{Zr_m, 1, argList{Yrl, Yml}},
 }
 
 var yml_mb = []ytab{
-	{Yrb, Ynone, Ymb, Zr_m, 1},
-	{Ymb, Ynone, Yrb, Zm_r, 1},
+	{Zr_m, 1, argList{Yrb, Ymb}},
+	{Zm_r, 1, argList{Ymb, Yrb}},
 }
 
 var yrb_mb = []ytab{
-	{Yrb, Ynone, Ymb, Zr_m, 1},
+	{Zr_m, 1, argList{Yrb, Ymb}},
 }
 
 var yxchg = []ytab{
-	{Yax, Ynone, Yrl, Z_rp, 1},
-	{Yrl, Ynone, Yax, Zrp_, 1},
-	{Yrl, Ynone, Yml, Zr_m, 1},
-	{Yml, Ynone, Yrl, Zm_r, 1},
+	{Z_rp, 1, argList{Yax, Yrl}},
+	{Zrp_, 1, argList{Yrl, Yax}},
+	{Zr_m, 1, argList{Yrl, Yml}},
+	{Zm_r, 1, argList{Yml, Yrl}},
 }
 
 var ydivl = []ytab{
-	{Yml, Ynone, Ynone, Zm_o, 2},
+	{Zm_o, 2, argList{Yml}},
 }
 
 var ydivb = []ytab{
-	{Ymb, Ynone, Ynone, Zm_o, 2},
+	{Zm_o, 2, argList{Ymb}},
 }
 
 var yimul = []ytab{
-	{Yml, Ynone, Ynone, Zm_o, 2},
-	{Yi8, Ynone, Yrl, Zib_rr, 1},
-	{Yi32, Ynone, Yrl, Zil_rr, 1},
-	{Yml, Ynone, Yrl, Zm_r, 2},
+	{Zm_o, 2, argList{Yml}},
+	{Zib_rr, 1, argList{Yi8, Yrl}},
+	{Zil_rr, 1, argList{Yi32, Yrl}},
+	{Zm_r, 2, argList{Yml, Yrl}},
 }
 
 var yimul3 = []ytab{
-	{Yi8, Yml, Yrl, Zibm_r, 2},
+	{Zibm_r, 2, argList{Yi8, Yml, Yrl}},
 }
 
 var ybyte = []ytab{
-	{Yi64, Ynone, Ynone, Zbyte, 1},
+	{Zbyte, 1, argList{Yi64}},
 }
 
 var yin = []ytab{
-	{Yi32, Ynone, Ynone, Zib_, 1},
-	{Ynone, Ynone, Ynone, Zlit, 1},
+	{Zib_, 1, argList{Yi32}},
+	{Zlit, 1, argList{}},
 }
 
 var yint = []ytab{
-	{Yi32, Ynone, Ynone, Zib_, 1},
+	{Zib_, 1, argList{Yi32}},
 }
 
 var ypushl = []ytab{
-	{Yrl, Ynone, Ynone, Zrp_, 1},
-	{Ym, Ynone, Ynone, Zm_o, 2},
-	{Yi8, Ynone, Ynone, Zib_, 1},
-	{Yi32, Ynone, Ynone, Zil_, 1},
+	{Zrp_, 1, argList{Yrl}},
+	{Zm_o, 2, argList{Ym}},
+	{Zib_, 1, argList{Yi8}},
+	{Zil_, 1, argList{Yi32}},
 }
 
 var ypopl = []ytab{
-	{Ynone, Ynone, Yrl, Z_rp, 1},
-	{Ynone, Ynone, Ym, Zo_m, 2},
+	{Z_rp, 1, argList{Yrl}},
+	{Zo_m, 2, argList{Ym}},
 }
 
 var yclflush = []ytab{
-	{Ynone, Ynone, Ym, Zo_m, 2},
+	{Zo_m, 2, argList{Ym}},
 }
 
 var ybswap = []ytab{
-	{Ynone, Ynone, Yrl, Z_rp, 2},
+	{Z_rp, 2, argList{Yrl}},
 }
 
 var yscond = []ytab{
-	{Ynone, Ynone, Ymb, Zo_m, 2},
+	{Zo_m, 2, argList{Ymb}},
 }
 
 var yjcond = []ytab{
-	{Ynone, Ynone, Ybr, Zbr, 0},
-	{Yi0, Ynone, Ybr, Zbr, 0},
-	{Yi1, Ynone, Ybr, Zbr, 1},
+	{Zbr, 0, argList{Ybr}},
+	{Zbr, 0, argList{Yi0, Ybr}},
+	{Zbr, 1, argList{Yi1, Ybr}},
 }
 
 var yloop = []ytab{
-	{Ynone, Ynone, Ybr, Zloop, 1},
+	{Zloop, 1, argList{Ybr}},
 }
 
 var ycall = []ytab{
-	{Ynone, Ynone, Yml, Zcallindreg, 0},
-	{Yrx, Ynone, Yrx, Zcallindreg, 2},
-	{Ynone, Ynone, Yindir, Zcallind, 2},
-	{Ynone, Ynone, Ybr, Zcall, 0},
-	{Ynone, Ynone, Yi32, Zcallcon, 1},
+	{Zcallindreg, 0, argList{Yml}},
+	{Zcallindreg, 2, argList{Yrx, Yrx}},
+	{Zcallind, 2, argList{Yindir}},
+	{Zcall, 0, argList{Ybr}},
+	{Zcallcon, 1, argList{Yi32}},
 }
 
 var yduff = []ytab{
-	{Ynone, Ynone, Yi32, Zcallduff, 1},
+	{Zcallduff, 1, argList{Yi32}},
 }
 
 var yjmp = []ytab{
-	{Ynone, Ynone, Yml, Zo_m64, 2},
-	{Ynone, Ynone, Ybr, Zjmp, 0},
-	{Ynone, Ynone, Yi32, Zjmpcon, 1},
+	{Zo_m64, 2, argList{Yml}},
+	{Zjmp, 0, argList{Ybr}},
+	{Zjmpcon, 1, argList{Yi32}},
 }
 
 var yfmvd = []ytab{
-	{Ym, Ynone, Yf0, Zm_o, 2},
-	{Yf0, Ynone, Ym, Zo_m, 2},
-	{Yrf, Ynone, Yf0, Zm_o, 2},
-	{Yf0, Ynone, Yrf, Zo_m, 2},
+	{Zm_o, 2, argList{Ym, Yf0}},
+	{Zo_m, 2, argList{Yf0, Ym}},
+	{Zm_o, 2, argList{Yrf, Yf0}},
+	{Zo_m, 2, argList{Yf0, Yrf}},
 }
 
 var yfmvdp = []ytab{
-	{Yf0, Ynone, Ym, Zo_m, 2},
-	{Yf0, Ynone, Yrf, Zo_m, 2},
+	{Zo_m, 2, argList{Yf0, Ym}},
+	{Zo_m, 2, argList{Yf0, Yrf}},
 }
 
 var yfmvf = []ytab{
-	{Ym, Ynone, Yf0, Zm_o, 2},
-	{Yf0, Ynone, Ym, Zo_m, 2},
+	{Zm_o, 2, argList{Ym, Yf0}},
+	{Zo_m, 2, argList{Yf0, Ym}},
 }
 
 var yfmvx = []ytab{
-	{Ym, Ynone, Yf0, Zm_o, 2},
+	{Zm_o, 2, argList{Ym, Yf0}},
 }
 
 var yfmvp = []ytab{
-	{Yf0, Ynone, Ym, Zo_m, 2},
+	{Zo_m, 2, argList{Yf0, Ym}},
 }
 
 var yfcmv = []ytab{
-	{Yrf, Ynone, Yf0, Zm_o, 2},
+	{Zm_o, 2, argList{Yrf, Yf0}},
 }
 
 var yfadd = []ytab{
-	{Ym, Ynone, Yf0, Zm_o, 2},
-	{Yrf, Ynone, Yf0, Zm_o, 2},
-	{Yf0, Ynone, Yrf, Zo_m, 2},
+	{Zm_o, 2, argList{Ym, Yf0}},
+	{Zm_o, 2, argList{Yrf, Yf0}},
+	{Zo_m, 2, argList{Yf0, Yrf}},
 }
 
 var yfxch = []ytab{
-	{Yf0, Ynone, Yrf, Zo_m, 2},
-	{Yrf, Ynone, Yf0, Zm_o, 2},
+	{Zo_m, 2, argList{Yf0, Yrf}},
+	{Zm_o, 2, argList{Yrf, Yf0}},
 }
 
 var ycompp = []ytab{
-	{Yf0, Ynone, Yrf, Zo_m, 2}, /* botch is really f0,f1 */
+	{Zo_m, 2, argList{Yf0, Yrf}}, /* botch is really f0,f1 */
 }
 
 var ystsw = []ytab{
-	{Ynone, Ynone, Ym, Zo_m, 2},
-	{Ynone, Ynone, Yax, Zlit, 1},
+	{Zo_m, 2, argList{Ym}},
+	{Zlit, 1, argList{Yax}},
+}
+
+var ysvrs_mo = []ytab{
+	{Zm_o, 2, argList{Ym}},
 }
 
-var ysvrs = []ytab{
-	{Ynone, Ynone, Ym, Zo_m, 2},
-	{Ym, Ynone, Ynone, Zm_o, 2},
+// unaryDst version of "ysvrs_mo".
+var ysvrs_om = []ytab{
+	{Zo_m, 2, argList{Ym}},
 }
 
 var ymm = []ytab{
-	{Ymm, Ynone, Ymr, Zm_r_xm, 1},
-	{Yxm, Ynone, Yxr, Zm_r_xm, 2},
+	{Zm_r_xm, 1, argList{Ymm, Ymr}},
+	{Zm_r_xm, 2, argList{Yxm, Yxr}},
 }
 
 var yxm = []ytab{
-	{Yxm, Ynone, Yxr, Zm_r_xm, 1},
+	{Zm_r_xm, 1, argList{Yxm, Yxr}},
 }
 
 var yxm_q4 = []ytab{
-	{Yxm, Ynone, Yxr, Zm_r, 1},
+	{Zm_r, 1, argList{Yxm, Yxr}},
 }
 
 var yxcvm1 = []ytab{
-	{Yxm, Ynone, Yxr, Zm_r_xm, 2},
-	{Yxm, Ynone, Ymr, Zm_r_xm, 2},
+	{Zm_r_xm, 2, argList{Yxm, Yxr}},
+	{Zm_r_xm, 2, argList{Yxm, Ymr}},
 }
 
 var yxcvm2 = []ytab{
-	{Yxm, Ynone, Yxr, Zm_r_xm, 2},
-	{Ymm, Ynone, Yxr, Zm_r_xm, 2},
+	{Zm_r_xm, 2, argList{Yxm, Yxr}},
+	{Zm_r_xm, 2, argList{Ymm, Yxr}},
 }
 
 var yxr = []ytab{
-	{Yxr, Ynone, Yxr, Zm_r_xm, 1},
+	{Zm_r_xm, 1, argList{Yxr, Yxr}},
 }
 
 var yxr_ml = []ytab{
-	{Yxr, Ynone, Yml, Zr_m_xm, 1},
+	{Zr_m_xm, 1, argList{Yxr, Yml}},
 }
 
 var ymr = []ytab{
-	{Ymr, Ynone, Ymr, Zm_r, 1},
+	{Zm_r, 1, argList{Ymr, Ymr}},
 }
 
 var ymr_ml = []ytab{
-	{Ymr, Ynone, Yml, Zr_m_xm, 1},
+	{Zr_m_xm, 1, argList{Ymr, Yml}},
 }
 
 var yxcmpi = []ytab{
-	{Yxm, Yxr, Yi8, Zm_r_i_xm, 2},
+	{Zm_r_i_xm, 2, argList{Yxm, Yxr, Yi8}},
 }
 
 var yxmov = []ytab{
-	{Yxm, Ynone, Yxr, Zm_r_xm, 1},
-	{Yxr, Ynone, Yxm, Zr_m_xm, 1},
+	{Zm_r_xm, 1, argList{Yxm, Yxr}},
+	{Zr_m_xm, 1, argList{Yxr, Yxm}},
 }
 
 var yxcvfl = []ytab{
-	{Yxm, Ynone, Yrl, Zm_r_xm, 1},
+	{Zm_r_xm, 1, argList{Yxm, Yrl}},
 }
 
 var yxcvlf = []ytab{
-	{Yml, Ynone, Yxr, Zm_r_xm, 1},
+	{Zm_r_xm, 1, argList{Yml, Yxr}},
 }
 
 var yxcvfq = []ytab{
-	{Yxm, Ynone, Yrl, Zm_r_xm, 2},
+	{Zm_r_xm, 2, argList{Yxm, Yrl}},
 }
 
 var yxcvqf = []ytab{
-	{Yml, Ynone, Yxr, Zm_r_xm, 2},
+	{Zm_r_xm, 2, argList{Yml, Yxr}},
 }
 
 var yps = []ytab{
-	{Ymm, Ynone, Ymr, Zm_r_xm, 1},
-	{Yi8, Ynone, Ymr, Zibo_m_xm, 2},
-	{Yxm, Ynone, Yxr, Zm_r_xm, 2},
-	{Yi8, Ynone, Yxr, Zibo_m_xm, 3},
+	{Zm_r_xm, 1, argList{Ymm, Ymr}},
+	{Zibo_m_xm, 2, argList{Yi8, Ymr}},
+	{Zm_r_xm, 2, argList{Yxm, Yxr}},
+	{Zibo_m_xm, 3, argList{Yi8, Yxr}},
 }
 
 var yxrrl = []ytab{
-	{Yxr, Ynone, Yrl, Zm_r, 1},
+	{Zm_r, 1, argList{Yxr, Yrl}},
 }
 
 var ymrxr = []ytab{
-	{Ymr, Ynone, Yxr, Zm_r, 1},
-	{Yxm, Ynone, Yxr, Zm_r_xm, 1},
+	{Zm_r, 1, argList{Ymr, Yxr}},
+	{Zm_r_xm, 1, argList{Yxm, Yxr}},
 }
 
 var ymshuf = []ytab{
-	{Yi8, Ymm, Ymr, Zibm_r, 2},
+	{Zibm_r, 2, argList{Yi8, Ymm, Ymr}},
 }
 
 var ymshufb = []ytab{
-	{Yxm, Ynone, Yxr, Zm2_r, 2},
+	{Zm2_r, 2, argList{Yxm, Yxr}},
 }
 
 // It should never have more than 1 entry,
@@ -739,60 +735,60 @@ var ymshufb = []ytab{
 // ROUNDPD and ROUNDPS and recently added BLENDPD,
 // to name a few.
 var yxshuf = []ytab{
-	{Yu8, Yxm, Yxr, Zibm_r, 2},
+	{Zibm_r, 2, argList{Yu8, Yxm, Yxr}},
 }
 
 var yextrw = []ytab{
-	{Yu8, Yxr, Yrl, Zibm_r, 2},
+	{Zibm_r, 2, argList{Yu8, Yxr, Yrl}},
 }
 
 var yextr = []ytab{
-	{Yu8, Yxr, Ymm, Zibr_m, 3},
+	{Zibr_m, 3, argList{Yu8, Yxr, Ymm}},
 }
 
 var yinsrw = []ytab{
-	{Yu8, Yml, Yxr, Zibm_r, 2},
+	{Zibm_r, 2, argList{Yu8, Yml, Yxr}},
 }
 
 var yinsr = []ytab{
-	{Yu8, Ymm, Yxr, Zibm_r, 3},
+	{Zibm_r, 3, argList{Yu8, Ymm, Yxr}},
 }
 
 var ypsdq = []ytab{
-	{Yi8, Ynone, Yxr, Zibo_m, 2},
+	{Zibo_m, 2, argList{Yi8, Yxr}},
 }
 
 var ymskb = []ytab{
-	{Yxr, Ynone, Yrl, Zm_r_xm, 2},
-	{Ymr, Ynone, Yrl, Zm_r_xm, 1},
+	{Zm_r_xm, 2, argList{Yxr, Yrl}},
+	{Zm_r_xm, 1, argList{Ymr, Yrl}},
 }
 
 var ycrc32l = []ytab{
-	{Yml, Ynone, Yrl, Zlitm_r, 0},
+	{Zlitm_r, 0, argList{Yml, Yrl}},
 }
 
 var yprefetch = []ytab{
-	{Ym, Ynone, Ynone, Zm_o, 2},
+	{Zm_o, 2, argList{Ym}},
 }
 
 var yaes = []ytab{
-	{Yxm, Ynone, Yxr, Zlitm_r, 2},
+	{Zlitm_r, 2, argList{Yxm, Yxr}},
 }
 
 var yxbegin = []ytab{
-	{Ynone, Ynone, Ybr, Zjmp, 1},
+	{Zjmp, 1, argList{Ybr}},
 }
 
 var yxabort = []ytab{
-	{Yu8, Ynone, Ynone, Zib_, 1},
+	{Zib_, 1, argList{Yu8}},
 }
 
 var ylddqu = []ytab{
-	{Ym, Ynone, Yxr, Zm_r, 1},
+	{Zm_r, 1, argList{Ym, Yxr}},
 }
 
 var ypalignr = []ytab{
-	{Yu8, Yxm, Yxr, Zibm_r, 2},
+	{Zibm_r, 2, argList{Yu8, Yxm, Yxr}},
 }
 
 // VEX instructions that come in two forms:
@@ -815,87 +811,87 @@ var ypalignr = []ytab{
 //	{AVPXOR, yvex_xy3, Pvex, [23]uint8{VEX_128_66_0F_WIG, 0xEF, VEX_256_66_0F_WIG, 0xEF}}
 //
 var yvex_xy3 = []ytab{
-	{Yxm, Yxr, Yxr, Zvex_rm_v_r, 2},
-	{Yym, Yyr, Yyr, Zvex_rm_v_r, 2},
+	{Zvex_rm_v_r, 2, argList{Yxm, Yxr, Yxr}},
+	{Zvex_rm_v_r, 2, argList{Yym, Yyr, Yyr}},
 }
 
 var yvex_x3 = []ytab{
-	{Yxm, Yxr, Yxr, Zvex_rm_v_r, 2},
+	{Zvex_rm_v_r, 2, argList{Yxm, Yxr, Yxr}},
 }
 
 var yvex_ri3 = []ytab{
-	{Yi8, Ymb, Yrl, Zvex_i_rm_r, 2},
+	{Zvex_i_rm_r, 2, argList{Yi8, Ymb, Yrl}},
 }
 
 var yvex_xyi3 = []ytab{
-	{Yu8, Yxm, Yxr, Zvex_i_rm_r, 2},
-	{Yu8, Yym, Yyr, Zvex_i_rm_r, 2},
-	{Yi8, Yxm, Yxr, Zvex_i_rm_r, 2},
-	{Yi8, Yym, Yyr, Zvex_i_rm_r, 2},
+	{Zvex_i_rm_r, 2, argList{Yu8, Yxm, Yxr}},
+	{Zvex_i_rm_r, 2, argList{Yu8, Yym, Yyr}},
+	{Zvex_i_rm_r, 2, argList{Yi8, Yxm, Yxr}},
+	{Zvex_i_rm_r, 2, argList{Yi8, Yym, Yyr}},
 }
 
-var yvex_yyi4 = []ytab{ //TODO don't hide 4 op, some version have xmm version
-	{Yym, Yyr, Yyr, Zvex_i_rm_v_r, 2},
+var yvex_yyi4 = []ytab{
+	{Zvex_i_rm_v_r, 2, argList{Yu8, Yym, Yyr, Yyr}},
 }
 
 var yvex_xyi4 = []ytab{
-	{Yxm, Yyr, Yyr, Zvex_i_rm_v_r, 2},
+	{Zvex_i_rm_v_r, 2, argList{Yu8, Yxm, Yyr, Yyr}},
 }
 
 var yvex_shift = []ytab{
-	{Yi8, Yxr, Yxr, Zvex_i_r_v, 3},
-	{Yi8, Yyr, Yyr, Zvex_i_r_v, 3},
-	{Yxm, Yxr, Yxr, Zvex_rm_v_r, 2},
-	{Yxm, Yyr, Yyr, Zvex_rm_v_r, 2},
+	{Zvex_i_r_v, 3, argList{Yi8, Yxr, Yxr}},
+	{Zvex_i_r_v, 3, argList{Yi8, Yyr, Yyr}},
+	{Zvex_rm_v_r, 2, argList{Yxm, Yxr, Yxr}},
+	{Zvex_rm_v_r, 2, argList{Yxm, Yyr, Yyr}},
 }
 
 var yvex_shift_dq = []ytab{
-	{Yi8, Yxr, Yxr, Zvex_i_r_v, 3},
-	{Yi8, Yyr, Yyr, Zvex_i_r_v, 3},
+	{Zvex_i_r_v, 3, argList{Yi8, Yxr, Yxr}},
+	{Zvex_i_r_v, 3, argList{Yi8, Yyr, Yyr}},
 }
 
 var yvex_r3 = []ytab{
-	{Yml, Yrl, Yrl, Zvex_rm_v_r, 2},
+	{Zvex_rm_v_r, 2, argList{Yml, Yrl, Yrl}},
 }
 
 var yvex_vmr3 = []ytab{
-	{Yrl, Yml, Yrl, Zvex_v_rm_r, 2},
+	{Zvex_v_rm_r, 2, argList{Yrl, Yml, Yrl}},
 }
 
 var yvex_xy2 = []ytab{
-	{Yxm, Ynone, Yxr, Zvex_rm_v_r, 2},
-	{Yym, Ynone, Yyr, Zvex_rm_v_r, 2},
+	{Zvex_rm_v_r, 2, argList{Yxm, Yxr}},
+	{Zvex_rm_v_r, 2, argList{Yym, Yyr}},
 }
 
 var yvex_xyr2 = []ytab{
-	{Yxr, Ynone, Yrl, Zvex_rm_v_r, 2},
-	{Yyr, Ynone, Yrl, Zvex_rm_v_r, 2},
+	{Zvex_rm_v_r, 2, argList{Yxr, Yrl}},
+	{Zvex_rm_v_r, 2, argList{Yyr, Yrl}},
 }
 
 var yvex_vmovdqa = []ytab{
-	{Yxm, Ynone, Yxr, Zvex_rm_v_r, 2},
-	{Yxr, Ynone, Yxm, Zvex_r_v_rm, 2},
-	{Yym, Ynone, Yyr, Zvex_rm_v_r, 2},
-	{Yyr, Ynone, Yym, Zvex_r_v_rm, 2},
+	{Zvex_rm_v_r, 2, argList{Yxm, Yxr}},
+	{Zvex_r_v_rm, 2, argList{Yxr, Yxm}},
+	{Zvex_rm_v_r, 2, argList{Yym, Yyr}},
+	{Zvex_r_v_rm, 2, argList{Yyr, Yym}},
 }
 
 var yvex_vmovntdq = []ytab{
-	{Yxr, Ynone, Ym, Zvex_r_v_rm, 2},
-	{Yyr, Ynone, Ym, Zvex_r_v_rm, 2},
+	{Zvex_r_v_rm, 2, argList{Yxr, Ym}},
+	{Zvex_r_v_rm, 2, argList{Yyr, Ym}},
 }
 
 var yvex_vpbroadcast = []ytab{
-	{Yxm, Ynone, Yxr, Zvex_rm_v_r, 2},
-	{Yxm, Ynone, Yyr, Zvex_rm_v_r, 2},
+	{Zvex_rm_v_r, 2, argList{Yxm, Yxr}},
+	{Zvex_rm_v_r, 2, argList{Yxm, Yyr}},
 }
 
 var yvex_vpbroadcast_sd = []ytab{
-	{Yxm, Ynone, Yyr, Zvex_rm_v_r, 2},
+	{Zvex_rm_v_r, 2, argList{Yxm, Yyr}},
 }
 
 var ymmxmm0f38 = []ytab{
-	{Ymm, Ynone, Ymr, Zlitm_r, 3},
-	{Yxm, Ynone, Yxr, Zlitm_r, 5},
+	{Zlitm_r, 3, argList{Ymm, Ymr}},
+	{Zlitm_r, 5, argList{Yxm, Yxr}},
 }
 
 /*
@@ -1120,10 +1116,10 @@ var optab =
 	{ADPPS, yxshuf, Pq, [23]uint8{0x3a, 0x40, 0}},
 	{AEMMS, ynone, Pm, [23]uint8{0x77}},
 	{AENTER, nil, 0, [23]uint8{}}, /* botch */
-	{AFXRSTOR, ysvrs, Pm, [23]uint8{0xae, 01, 0xae, 01}},
-	{AFXSAVE, ysvrs, Pm, [23]uint8{0xae, 00, 0xae, 00}},
-	{AFXRSTOR64, ysvrs, Pw, [23]uint8{0x0f, 0xae, 01, 0x0f, 0xae, 01}},
-	{AFXSAVE64, ysvrs, Pw, [23]uint8{0x0f, 0xae, 00, 0x0f, 0xae, 00}},
+	{AFXRSTOR, ysvrs_mo, Pm, [23]uint8{0xae, 01, 0xae, 01}},
+	{AFXSAVE, ysvrs_om, Pm, [23]uint8{0xae, 00, 0xae, 00}},
+	{AFXRSTOR64, ysvrs_mo, Pw, [23]uint8{0x0f, 0xae, 01, 0x0f, 0xae, 01}},
+	{AFXSAVE64, ysvrs_om, Pw, [23]uint8{0x0f, 0xae, 00, 0x0f, 0xae, 00}},
 	{AHLT, ynone, Px, [23]uint8{0xf4}},
 	{AIDIVB, ydivb, Pb, [23]uint8{0xf6, 07}},
 	{AIDIVL, ydivl, Px, [23]uint8{0xf7, 07}},
@@ -1178,7 +1174,7 @@ var optab =
 	{ALARL, yml_rl, Pm, [23]uint8{0x02}},
 	{ALARW, yml_rl, Pq, [23]uint8{0x02}},
 	{ALDDQU, ylddqu, Pf2, [23]uint8{0xf0}},
-	{ALDMXCSR, ysvrs, Pm, [23]uint8{0xae, 02, 0xae, 02}},
+	{ALDMXCSR, ysvrs_mo, Pm, [23]uint8{0xae, 02, 0xae, 02}},
 	{ALEAL, ym_rl, Px, [23]uint8{0x8d}},
 	{ALEAQ, ym_rl, Pw, [23]uint8{0x8d}},
 	{ALEAVEL, ynone, P32, [23]uint8{0xc9}},
@@ -1493,7 +1489,7 @@ var optab =
 	{ASTC, ynone, Px, [23]uint8{0xf9}},
 	{ASTD, ynone, Px, [23]uint8{0xfd}},
 	{ASTI, ynone, Px, [23]uint8{0xfb}},
-	{ASTMXCSR, ysvrs, Pm, [23]uint8{0xae, 03, 0xae, 03}},
+	{ASTMXCSR, ysvrs_om, Pm, [23]uint8{0xae, 03, 0xae, 03}},
 	{ASTOSB, ynone, Pb, [23]uint8{0xaa}},
 	{ASTOSL, ynone, Px, [23]uint8{0xab}},
 	{ASTOSQ, ynone, Pw, [23]uint8{0xab}},
@@ -1604,12 +1600,12 @@ var optab =
 	{AFDIVRD, yfadd, Px, [23]uint8{0xdc, 07, 0xd8, 07, 0xdc, 06}},
 	{AFXCHD, yfxch, Px, [23]uint8{0xd9, 01, 0xd9, 01}},
 	{AFFREE, nil, 0, [23]uint8{}},
-	{AFLDCW, ysvrs, Px, [23]uint8{0xd9, 05, 0xd9, 05}},
-	{AFLDENV, ysvrs, Px, [23]uint8{0xd9, 04, 0xd9, 04}},
-	{AFRSTOR, ysvrs, Px, [23]uint8{0xdd, 04, 0xdd, 04}},
-	{AFSAVE, ysvrs, Px, [23]uint8{0xdd, 06, 0xdd, 06}},
-	{AFSTCW, ysvrs, Px, [23]uint8{0xd9, 07, 0xd9, 07}},
-	{AFSTENV, ysvrs, Px, [23]uint8{0xd9, 06, 0xd9, 06}},
+	{AFLDCW, ysvrs_mo, Px, [23]uint8{0xd9, 05, 0xd9, 05}},
+	{AFLDENV, ysvrs_mo, Px, [23]uint8{0xd9, 04, 0xd9, 04}},
+	{AFRSTOR, ysvrs_mo, Px, [23]uint8{0xdd, 04, 0xdd, 04}},
+	{AFSAVE, ysvrs_om, Px, [23]uint8{0xdd, 06, 0xdd, 06}},
+	{AFSTCW, ysvrs_om, Px, [23]uint8{0xd9, 07, 0xd9, 07}},
+	{AFSTENV, ysvrs_om, Px, [23]uint8{0xd9, 06, 0xd9, 06}},
 	{AFSTSW, ystsw, Px, [23]uint8{0xdd, 07, 0xdf, 0xe0}},
 	{AF2XM1, ynone, Px, [23]uint8{0xd9, 0xf0}},
 	{AFABS, ynone, Px, [23]uint8{0xd9, 0xe1}},
@@ -3403,9 +3399,10 @@ func (asmbuf *AsmBuf) doasm(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog) {
 	// Similarly SHRQ CX, AX:DX is really SHRQ CX(DX*0), AX.
 	// Change encoding generated by assemblers and compilers and remove.
 	if (p.From.Type == obj.TYPE_CONST || p.From.Type == obj.TYPE_REG) && p.From.Index != REG_NONE && p.From.Scale == 0 {
-		p.From3 = new(obj.Addr)
-		p.From3.Type = obj.TYPE_REG
-		p.From3.Reg = p.From.Index
+		p.SetFrom3(obj.Addr{
+			Type: obj.TYPE_REG,
+			Reg:  p.From.Index,
+		})
 		p.From.Index = 0
 	}
 
@@ -3414,8 +3411,7 @@ func (asmbuf *AsmBuf) doasm(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog) {
 	switch p.As {
 	case AIMUL3Q, APEXTRW, APINSRW, APINSRD, APINSRQ, APSHUFHW, APSHUFL, APSHUFW, ASHUFPD, ASHUFPS, AAESKEYGENASSIST, APSHUFD, APCLMULQDQ:
 		if p.From3Type() == obj.TYPE_NONE {
-			p.From3 = new(obj.Addr)
-			*p.From3 = p.From
+			p.SetFrom3(p.From)
 			p.From = obj.Addr{}
 			p.From.Type = obj.TYPE_CONST
 			p.From.Offset = p.To.Offset
@@ -3423,12 +3419,11 @@ func (asmbuf *AsmBuf) doasm(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog) {
 		}
 	case ACMPSD, ACMPSS, ACMPPS, ACMPPD:
 		if p.From3Type() == obj.TYPE_NONE {
-			p.From3 = new(obj.Addr)
-			*p.From3 = p.To
+			p.SetFrom3(p.To)
 			p.To = obj.Addr{}
 			p.To.Type = obj.TYPE_CONST
-			p.To.Offset = p.From3.Offset
-			p.From3.Offset = 0
+			p.To.Offset = p.GetFrom3().Offset
+			p.GetFrom3().Offset = 0
 		}
 	}
 
@@ -3440,10 +3435,7 @@ func (asmbuf *AsmBuf) doasm(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog) {
 	}
 
 	ft := int(p.Ft) * Ymax
-	f3t := Ynone * Ymax
-	if p.From3 != nil {
-		f3t = oclass(ctxt, p, p.From3) * Ymax
-	}
+	var f3t int
 	tt := int(p.Tt) * Ymax
 
 	xo := obj.Bool2int(o.op[0] == 0x0f)
@@ -3455,9 +3447,22 @@ func (asmbuf *AsmBuf) doasm(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog) {
 	var r *obj.Reloc
 	var rel obj.Reloc
 	var v int64
-	for i := range o.ytab {
-		yt := &o.ytab[i]
-		if ycover[ft+int(yt.from)] != 0 && ycover[f3t+int(yt.from3)] != 0 && ycover[tt+int(yt.to)] != 0 {
+
+	args := make([]int, 0, 6)
+	if ft != Ynone*Ymax {
+		args = append(args, ft)
+	}
+	for i := range p.RestArgs {
+		args = append(args, oclass(ctxt, p, &p.RestArgs[i])*Ymax)
+	}
+	if tt != Ynone*Ymax {
+		args = append(args, tt)
+	}
+
+	for _, yt := range o.ytab {
+		if !yt.match(args) {
+			z += int(yt.zoffset) + xo
+		} else {
 			switch o.prefix {
 			case Px1: /* first option valid only in 32-bit mode */
 				if ctxt.Arch.Family == sys.AMD64 && z == 0 {
@@ -3604,7 +3609,7 @@ func (asmbuf *AsmBuf) doasm(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog) {
 
 			case Zm_r_i_xm:
 				asmbuf.mediaop(ctxt, o, op, int(yt.zoffset), z)
-				asmbuf.asmand(ctxt, cursym, p, &p.From, p.From3)
+				asmbuf.asmand(ctxt, cursym, p, &p.From, p.GetFrom3())
 				asmbuf.Put1(byte(p.To.Offset))
 
 			case Zibm_r, Zibr_m:
@@ -3618,9 +3623,9 @@ func (asmbuf *AsmBuf) doasm(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog) {
 					asmbuf.Put1(byte(op))
 				}
 				if yt.zcase == Zibr_m {
-					asmbuf.asmand(ctxt, cursym, p, &p.To, p.From3)
+					asmbuf.asmand(ctxt, cursym, p, &p.To, p.GetFrom3())
 				} else {
-					asmbuf.asmand(ctxt, cursym, p, p.From3, &p.To)
+					asmbuf.asmand(ctxt, cursym, p, p.GetFrom3(), &p.To)
 				}
 				asmbuf.Put1(byte(p.From.Offset))
 
@@ -3642,36 +3647,37 @@ func (asmbuf *AsmBuf) doasm(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog) {
 				asmbuf.asmand(ctxt, cursym, p, &p.To, &p.From)
 
 			case Zvex_rm_v_r:
-				asmbuf.asmvex(ctxt, &p.From, p.From3, &p.To, o.op[z], o.op[z+1])
+				asmbuf.asmvex(ctxt, &p.From, p.GetFrom3(), &p.To, o.op[z], o.op[z+1])
 				asmbuf.asmand(ctxt, cursym, p, &p.From, &p.To)
 
 			case Zvex_i_r_v:
-				asmbuf.asmvex(ctxt, p.From3, &p.To, nil, o.op[z], o.op[z+1])
+				asmbuf.asmvex(ctxt, p.GetFrom3(), &p.To, nil, o.op[z], o.op[z+1])
 				regnum := byte(0x7)
-				if p.From3.Reg >= REG_X0 && p.From3.Reg <= REG_X15 {
-					regnum &= byte(p.From3.Reg - REG_X0)
+				if p.GetFrom3().Reg >= REG_X0 && p.GetFrom3().Reg <= REG_X15 {
+					regnum &= byte(p.GetFrom3().Reg - REG_X0)
 				} else {
-					regnum &= byte(p.From3.Reg - REG_Y0)
+					regnum &= byte(p.GetFrom3().Reg - REG_Y0)
 				}
 				asmbuf.Put1(byte(o.op[z+2]) | regnum)
 				asmbuf.Put1(byte(p.From.Offset))
 
 			case Zvex_i_rm_v_r:
-				asmbuf.asmvex(ctxt, &p.From, p.From3, &p.To, o.op[z], o.op[z+1])
-				asmbuf.asmand(ctxt, cursym, p, &p.From, &p.To)
-				asmbuf.Put1(byte(p.From3.Offset))
+				imm, from, from3, to := unpackOps4(p)
+				asmbuf.asmvex(ctxt, from, from3, to, o.op[z], o.op[z+1])
+				asmbuf.asmand(ctxt, cursym, p, from, to)
+				asmbuf.Put1(byte(imm.Offset))
 
 			case Zvex_i_rm_r:
-				asmbuf.asmvex(ctxt, p.From3, nil, &p.To, o.op[z], o.op[z+1])
-				asmbuf.asmand(ctxt, cursym, p, p.From3, &p.To)
+				asmbuf.asmvex(ctxt, p.GetFrom3(), nil, &p.To, o.op[z], o.op[z+1])
+				asmbuf.asmand(ctxt, cursym, p, p.GetFrom3(), &p.To)
 				asmbuf.Put1(byte(p.From.Offset))
 
 			case Zvex_v_rm_r:
-				asmbuf.asmvex(ctxt, p.From3, &p.From, &p.To, o.op[z], o.op[z+1])
-				asmbuf.asmand(ctxt, cursym, p, p.From3, &p.To)
+				asmbuf.asmvex(ctxt, p.GetFrom3(), &p.From, &p.To, o.op[z], o.op[z+1])
+				asmbuf.asmand(ctxt, cursym, p, p.GetFrom3(), &p.To)
 
 			case Zvex_r_v_rm:
-				asmbuf.asmvex(ctxt, &p.To, p.From3, &p.From, o.op[z], o.op[z+1])
+				asmbuf.asmvex(ctxt, &p.To, p.GetFrom3(), &p.From, o.op[z], o.op[z+1])
 				asmbuf.asmand(ctxt, cursym, p, &p.To, &p.From)
 
 			case Zr_m_xm:
@@ -4026,7 +4032,10 @@ func (asmbuf *AsmBuf) doasm(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog) {
 
 			return
 		}
-		z += int(yt.zoffset) + xo
+	}
+	f3t = Ynone * Ymax
+	if p.GetFrom3() != nil {
+		f3t = oclass(ctxt, p, p.GetFrom3()) * Ymax
 	}
 	for mo := ymovtab; mo[0].as != 0; mo = mo[1:] {
 		var pp obj.Prog
@@ -4105,7 +4114,7 @@ func (asmbuf *AsmBuf) doasm(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog) {
 
 					case obj.TYPE_CONST:
 						asmbuf.Put2(0x0f, t[0])
-						asmbuf.asmandsz(ctxt, cursym, p, &p.To, reg[p.From3.Reg], regrex[p.From3.Reg], 0)
+						asmbuf.asmandsz(ctxt, cursym, p, &p.To, reg[p.GetFrom3().Reg], regrex[p.GetFrom3().Reg], 0)
 						asmbuf.Put1(byte(p.From.Offset))
 
 					case obj.TYPE_REG:
@@ -4115,7 +4124,7 @@ func (asmbuf *AsmBuf) doasm(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog) {
 
 						case REG_CL, REG_CX:
 							asmbuf.Put2(0x0f, t[1])
-							asmbuf.asmandsz(ctxt, cursym, p, &p.To, reg[p.From3.Reg], regrex[p.From3.Reg], 0)
+							asmbuf.asmandsz(ctxt, cursym, p, &p.To, reg[p.GetFrom3().Reg], regrex[p.GetFrom3().Reg], 0)
 						}
 					}
 
@@ -4666,3 +4675,8 @@ func (asmbuf *AsmBuf) asmins(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog) {
 		}
 	}
 }
+
+// Extract 4 operands from p.
+func unpackOps4(p *obj.Prog) (*obj.Addr, *obj.Addr, *obj.Addr, *obj.Addr) {
+	return &p.From, &p.RestArgs[0], &p.RestArgs[1], &p.To
+}
diff --git a/src/cmd/internal/obj/x86/obj6.go b/src/cmd/internal/obj/x86/obj6.go
index 38aeb4a59d..0e6deafc91 100644
--- a/src/cmd/internal/obj/x86/obj6.go
+++ b/src/cmd/internal/obj/x86/obj6.go
@@ -201,8 +201,8 @@ func progedit(ctxt *obj.Link, p *obj.Prog, newprog obj.ProgAlloc) {
 	}
 
 	if ctxt.Headtype == objabi.Hnacl && ctxt.Arch.Family == sys.AMD64 {
-		if p.From3 != nil {
-			nacladdr(ctxt, p, p.From3)
+		if p.GetFrom3() != nil {
+			nacladdr(ctxt, p, p.GetFrom3())
 		}
 		nacladdr(ctxt, p, &p.From)
 		nacladdr(ctxt, p, &p.To)
@@ -398,7 +398,7 @@ func rewriteToUseGot(ctxt *obj.Link, p *obj.Prog, newprog obj.ProgAlloc) {
 			q.From.Reg = reg
 		}
 	}
-	if p.From3 != nil && p.From3.Name == obj.NAME_EXTERN {
+	if p.GetFrom3() != nil && p.GetFrom3().Name == obj.NAME_EXTERN {
 		ctxt.Diag("don't know how to handle %v with -dynlink", p)
 	}
 	var source *obj.Addr
@@ -436,7 +436,9 @@ func rewriteToUseGot(ctxt *obj.Link, p *obj.Prog, newprog obj.ProgAlloc) {
 		p2.As = p.As
 		p2.Scond = p.Scond
 		p2.From = p.From
-		p2.From3 = p.From3
+		if p.RestArgs != nil {
+			p2.RestArgs = append(p2.RestArgs, p.RestArgs...)
+		}
 		p2.Reg = p.Reg
 		p2.To = p.To
 		// p.To.Type was set to TYPE_BRANCH above, but that makes checkaddr
@@ -522,7 +524,7 @@ func rewriteToPcrel(ctxt *obj.Link, p *obj.Prog, newprog obj.ProgAlloc) {
 		}
 	}
 
-	if !isName(&p.From) && !isName(&p.To) && (p.From3 == nil || !isName(p.From3)) {
+	if !isName(&p.From) && !isName(&p.To) && (p.GetFrom3() == nil || !isName(p.GetFrom3())) {
 		return
 	}
 	var dst int16 = REG_CX
@@ -543,7 +545,7 @@ func rewriteToPcrel(ctxt *obj.Link, p *obj.Prog, newprog obj.ProgAlloc) {
 	r.As = p.As
 	r.Scond = p.Scond
 	r.From = p.From
-	r.From3 = p.From3
+	r.RestArgs = p.RestArgs
 	r.Reg = p.Reg
 	r.To = p.To
 	if isName(&p.From) {
@@ -552,8 +554,8 @@ func rewriteToPcrel(ctxt *obj.Link, p *obj.Prog, newprog obj.ProgAlloc) {
 	if isName(&p.To) {
 		r.To.Reg = dst
 	}
-	if p.From3 != nil && isName(p.From3) {
-		r.From3.Reg = dst
+	if p.GetFrom3() != nil && isName(p.GetFrom3()) {
+		r.GetFrom3().Reg = dst
 	}
 	obj.Nopout(p)
 }
@@ -857,12 +859,12 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
 		case obj.NAME_PARAM:
 			p.From.Offset += int64(deltasp) + int64(pcsize)
 		}
-		if p.From3 != nil {
-			switch p.From3.Name {
+		if p.GetFrom3() != nil {
+			switch p.GetFrom3().Name {
 			case obj.NAME_AUTO:
-				p.From3.Offset += int64(deltasp) - int64(bpsize)
+				p.GetFrom3().Offset += int64(deltasp) - int64(bpsize)
 			case obj.NAME_PARAM:
-				p.From3.Offset += int64(deltasp) + int64(pcsize)
+				p.GetFrom3().Offset += int64(deltasp) + int64(pcsize)
 			}
 		}
 		switch p.To.Name {
diff --git a/src/cmd/internal/obj/x86/ytab.go b/src/cmd/internal/obj/x86/ytab.go
new file mode 100644
index 0000000000..dbbef4730e
--- /dev/null
+++ b/src/cmd/internal/obj/x86/ytab.go
@@ -0,0 +1,40 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package x86
+
+type argList [6]uint8
+
+type ytab struct {
+	zcase   uint8
+	zoffset uint8
+
+	// Last arg is usually destination.
+	// For unary instructions unaryDst is used to determine
+	// if single argument is a source or destination.
+	args argList
+}
+
+// Returns true if yt is compatible with args.
+//
+// Elements from args and yt.args are used to
+// to index ycover table like `ycover[args[i]+yt.args[i]]`.
+// This means that args should contain values that already
+// multiplied by Ymax.
+func (yt *ytab) match(args []int) bool {
+	// Trailing Yxxx check is required to avoid a case
+	// where shorter arg list is matched.
+	// If we had exact yt.args length, it could be `yt.argc != len(args)`.
+	if len(args) < len(yt.args) && yt.args[len(args)] != Yxxx {
+		return false
+	}
+
+	for i := range args {
+		if ycover[args[i]+int(yt.args[i])] == 0 {
+			return false
+		}
+	}
+
+	return true
+}