cmd/compile,cmd/asm: simplify recording of branch targets, take 2

We currently use two fields to store the targets of branches.
Some phases use p.To.Val, some use p.Pcond. Rewrite so that
every branch instruction uses p.To.Val.
p.From.Val is also used in rare instances.
Introduce a Pool link for use by arm/arm64, instead of
repurposing Pcond.

This is a cleanup CL in preparation for some stack frame CLs.

Change-Id: If8239177e4b1ea2bccd0608eb39553d23210d405
Reviewed-on: https://go-review.googlesource.com/c/go/+/251437
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

1 files changed, 7 insertions, 10 deletions

diff --git a/src/cmd/internal/obj/pass.go b/src/cmd/internal/obj/pass.go
index 4f156d969b..09d520b4e9 100644
--- a/src/cmd/internal/obj/pass.go
+++ b/src/cmd/internal/obj/pass.go
@@ -36,8 +36,8 @@ package obj
 // In the case of an infinite loop, brloop returns nil.
 func brloop(p *Prog) *Prog {
 	c := 0
-	for q := p; q != nil; q = q.Pcond {
-		if q.As != AJMP || q.Pcond == nil {
+	for q := p; q != nil; q = q.To.Target() {
+		if q.As != AJMP || q.To.Target() == nil {
 			return q
 		}
 		c++
@@ -132,8 +132,6 @@ func linkpatch(ctxt *Link, sym *LSym, newprog ProgAlloc) {
 			continue
 		}
 		if p.To.Val != nil {
-			// TODO: Remove To.Val.(*Prog) in favor of p->pcond.
-			p.Pcond = p.To.Val.(*Prog)
 			continue
 		}
 
@@ -158,8 +156,7 @@ func linkpatch(ctxt *Link, sym *LSym, newprog ProgAlloc) {
 			p.To.Type = TYPE_NONE
 		}
 
-		p.To.Val = q
-		p.Pcond = q
+		p.To.SetTarget(q)
 	}
 
 	if !ctxt.Flag_optimize {
@@ -168,12 +165,12 @@ func linkpatch(ctxt *Link, sym *LSym, newprog ProgAlloc) {
 
 	// Collapse series of jumps to jumps.
 	for p := sym.Func.Text; p != nil; p = p.Link {
-		if p.Pcond == nil {
+		if p.To.Target() == nil {
 			continue
 		}
-		p.Pcond = brloop(p.Pcond)
-		if p.Pcond != nil && p.To.Type == TYPE_BRANCH {
-			p.To.Offset = p.Pcond.Pc
+		p.To.SetTarget(brloop(p.To.Target()))
+		if p.To.Target() != nil && p.To.Type == TYPE_BRANCH {
+			p.To.Offset = p.To.Target().Pc
 		}
 	}
 }