[dev.regabi] cmd/compile: limit Implicit method to nodes where it is defined

The general concept of an "implicit" operation is provided by every
expr representation, but it really only makes sense for a few of them,
and worse the exact definition of what "implicit" means differs from
node to node.

This CL moves the method to each node implementation, although
they all share the same header bit instead of each defining a bool field
that would turn into 8 bytes on 64-bit systems.

Now we can say precisely which Nodes have a meaningful Implicit
method: AddrExpr, CompLitExpr, ConvExpr, ParenExpr, and StarExpr.

Passes buildall w/ toolstash -cmp.

Change-Id: I7d85cb0507a514cdcb6eed21347f362e5fb57a91
Reviewed-on: https://go-review.googlesource.com/c/go/+/277918
Trust: Russ Cox <rsc@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

1 files changed, 30 insertions, 20 deletions

diff --git a/src/cmd/compile/internal/ir/expr.go b/src/cmd/compile/internal/ir/expr.go
index 8ea31c1929..36a11dad9a 100644
--- a/src/cmd/compile/internal/ir/expr.go
+++ b/src/cmd/compile/internal/ir/expr.go
@@ -52,10 +52,10 @@ type miniExpr struct {
 
 const (
 	miniExprHasCall = 1 << iota
-	miniExprImplicit
 	miniExprNonNil
 	miniExprTransient
 	miniExprBounded
+	miniExprImplicit // for use by implementations; not supported by every Expr
 )
 
 func (*miniExpr) isExpr() {}
@@ -66,8 +66,6 @@ func (n *miniExpr) Opt() interface{}      { return n.opt }
 func (n *miniExpr) SetOpt(x interface{})  { n.opt = x }
 func (n *miniExpr) HasCall() bool         { return n.flags&miniExprHasCall != 0 }
 func (n *miniExpr) SetHasCall(b bool)     { n.flags.set(miniExprHasCall, b) }
-func (n *miniExpr) Implicit() bool        { return n.flags&miniExprImplicit != 0 }
-func (n *miniExpr) SetImplicit(b bool)    { n.flags.set(miniExprImplicit, b) }
 func (n *miniExpr) NonNil() bool          { return n.flags&miniExprNonNil != 0 }
 func (n *miniExpr) MarkNonNil()           { n.flags |= miniExprNonNil }
 func (n *miniExpr) Transient() bool       { return n.flags&miniExprTransient != 0 }
@@ -121,10 +119,12 @@ func NewAddrExpr(pos src.XPos, x Node) *AddrExpr {
 	return n
 }
 
-func (n *AddrExpr) Left() Node      { return n.X }
-func (n *AddrExpr) SetLeft(x Node)  { n.X = x }
-func (n *AddrExpr) Right() Node     { return n.Alloc }
-func (n *AddrExpr) SetRight(x Node) { n.Alloc = x }
+func (n *AddrExpr) Left() Node         { return n.X }
+func (n *AddrExpr) SetLeft(x Node)     { n.X = x }
+func (n *AddrExpr) Right() Node        { return n.Alloc }
+func (n *AddrExpr) SetRight(x Node)    { n.Alloc = x }
+func (n *AddrExpr) Implicit() bool     { return n.flags&miniExprImplicit != 0 }
+func (n *AddrExpr) SetImplicit(b bool) { n.flags.set(miniExprImplicit, b) }
 
 func (n *AddrExpr) SetOp(op Op) {
 	switch op {
@@ -301,13 +301,15 @@ func NewCompLitExpr(pos src.XPos, op Op, typ Ntype, list []Node) *CompLitExpr {
 	return n
 }
 
-func (n *CompLitExpr) Orig() Node      { return n.orig }
-func (n *CompLitExpr) SetOrig(x Node)  { n.orig = x }
-func (n *CompLitExpr) Right() Node     { return n.Ntype }
-func (n *CompLitExpr) SetRight(x Node) { n.Ntype = toNtype(x) }
-func (n *CompLitExpr) List() Nodes     { return n.List_ }
-func (n *CompLitExpr) PtrList() *Nodes { return &n.List_ }
-func (n *CompLitExpr) SetList(x Nodes) { n.List_ = x }
+func (n *CompLitExpr) Orig() Node         { return n.orig }
+func (n *CompLitExpr) SetOrig(x Node)     { n.orig = x }
+func (n *CompLitExpr) Right() Node        { return n.Ntype }
+func (n *CompLitExpr) SetRight(x Node)    { n.Ntype = toNtype(x) }
+func (n *CompLitExpr) List() Nodes        { return n.List_ }
+func (n *CompLitExpr) PtrList() *Nodes    { return &n.List_ }
+func (n *CompLitExpr) SetList(x Nodes)    { n.List_ = x }
+func (n *CompLitExpr) Implicit() bool     { return n.flags&miniExprImplicit != 0 }
+func (n *CompLitExpr) SetImplicit(b bool) { n.flags.set(miniExprImplicit, b) }
 
 func (n *CompLitExpr) SetOp(op Op) {
 	switch op {
@@ -354,8 +356,10 @@ func NewConvExpr(pos src.XPos, op Op, typ *types.Type, x Node) *ConvExpr {
 	return n
 }
 
-func (n *ConvExpr) Left() Node     { return n.X }
-func (n *ConvExpr) SetLeft(x Node) { n.X = x }
+func (n *ConvExpr) Left() Node         { return n.X }
+func (n *ConvExpr) SetLeft(x Node)     { n.X = x }
+func (n *ConvExpr) Implicit() bool     { return n.flags&miniExprImplicit != 0 }
+func (n *ConvExpr) SetImplicit(b bool) { n.flags.set(miniExprImplicit, b) }
 
 func (n *ConvExpr) SetOp(op Op) {
 	switch op {
@@ -583,8 +587,10 @@ func NewParenExpr(pos src.XPos, x Node) *ParenExpr {
 	return n
 }
 
-func (n *ParenExpr) Left() Node     { return n.X }
-func (n *ParenExpr) SetLeft(x Node) { n.X = x }
+func (n *ParenExpr) Left() Node         { return n.X }
+func (n *ParenExpr) SetLeft(x Node)     { n.X = x }
+func (n *ParenExpr) Implicit() bool     { return n.flags&miniExprImplicit != 0 }
+func (n *ParenExpr) SetImplicit(b bool) { n.flags.set(miniExprImplicit, b) }
 
 func (*ParenExpr) CanBeNtype() {}
 
@@ -645,6 +651,8 @@ func (n *SelectorExpr) Sym() *types.Sym     { return n.Sel }
 func (n *SelectorExpr) SetSym(x *types.Sym) { n.Sel = x }
 func (n *SelectorExpr) Offset() int64       { return n.Offset_ }
 func (n *SelectorExpr) SetOffset(x int64)   { n.Offset_ = x }
+func (n *SelectorExpr) Implicit() bool      { return n.flags&miniExprImplicit != 0 }
+func (n *SelectorExpr) SetImplicit(b bool)  { n.flags.set(miniExprImplicit, b) }
 
 // Before type-checking, bytes.Buffer is a SelectorExpr.
 // After type-checking it becomes a Name.
@@ -783,8 +791,10 @@ func NewStarExpr(pos src.XPos, x Node) *StarExpr {
 	return n
 }
 
-func (n *StarExpr) Left() Node     { return n.X }
-func (n *StarExpr) SetLeft(x Node) { n.X = x }
+func (n *StarExpr) Left() Node         { return n.X }
+func (n *StarExpr) SetLeft(x Node)     { n.X = x }
+func (n *StarExpr) Implicit() bool     { return n.flags&miniExprImplicit != 0 }
+func (n *StarExpr) SetImplicit(b bool) { n.flags.set(miniExprImplicit, b) }
 
 func (*StarExpr) CanBeNtype() {}