[dev.regabi] cmd/compile: introduce FwdRefAux for wrapping ir.Node as ssa.Aux

OpFwdRef is the only SSA value that needs the ability to store an
arbitrary ir.Node in its Aux field. Every other SSA value always uses
an *ir.Name.

This CL introduces FwdRefAux, which wraps an ir.Node and implements
the ssa.Aux tag interface, so that a subsequent refactoring can change
ir.Node to not implement ssa.Aux.

Passes buildall w/ toolstash -cmp.

Updates #42982.

Change-Id: Id1475b28847579573cd376e82f28761d84cd1c23
Reviewed-on: https://go-review.googlesource.com/c/go/+/275788
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>

diff --git a/src/cmd/compile/internal/gc/phi.go b/src/cmd/compile/internal/gc/phi.go
index 677bfc92df2f1e6693650eeecda82abb4dbe37ca..def11e1be0cb287752bedd0d736660b9761b7cba 100644 (file)
--- a/src/cmd/compile/internal/gc/phi.go
+++ b/src/cmd/compile/internal/gc/phi.go
@@ -23,6 +23,14 @@ const smallBlocks = 500
 
 const debugPhi = false
 
+// FwdRefAux wraps an arbitrary ir.Node as an ssa.Aux for use with OpFwdref.
+type FwdRefAux struct {
+       _ [0]func() // ensure ir.Node isn't compared for equality
+       N ir.Node
+}
+
+func (FwdRefAux) CanBeAnSSAAux() {}
+
 // insertPhis finds all the places in the function where a phi is
 // necessary and inserts them.
 // Uses FwdRef ops to find all uses of variables, and s.defvars to find
@@ -79,7 +87,7 @@ func (s *phiState) insertPhis() {
                        if v.Op != ssa.OpFwdRef {
                                continue
                        }
-                       var_ := v.Aux.(ir.Node)
+                       var_ := v.Aux.(FwdRefAux).N
 
                        // Optimization: look back 1 block for the definition.
                        if len(b.Preds) == 1 {
@@ -319,7 +327,7 @@ func (s *phiState) resolveFwdRefs() {
                        if v.Op != ssa.OpFwdRef {
                                continue
                        }
-                       n := s.varnum[v.Aux.(ir.Node)]
+                       n := s.varnum[v.Aux.(FwdRefAux).N]
                        v.Op = ssa.OpCopy
                        v.Aux = nil
                        v.AddArg(values[n])
@@ -450,7 +458,7 @@ func (s *simplePhiState) insertPhis() {
                                continue
                        }
                        s.fwdrefs = append(s.fwdrefs, v)
-                       var_ := v.Aux.(ir.Node)
+                       var_ := v.Aux.(FwdRefAux).N
                        if _, ok := s.defvars[b.ID][var_]; !ok {
                                s.defvars[b.ID][var_] = v // treat FwdDefs as definitions.
                        }
@@ -464,7 +472,7 @@ loop:
                v := s.fwdrefs[len(s.fwdrefs)-1]
                s.fwdrefs = s.fwdrefs[:len(s.fwdrefs)-1]
                b := v.Block
-               var_ := v.Aux.(ir.Node)
+               var_ := v.Aux.(FwdRefAux).N
                if b == s.f.Entry {
                        // No variable should be live at entry.
                        s.s.Fatalf("Value live at entry. It shouldn't be. func %s, node %v, value %v", s.f.Name, var_, v)
@@ -531,7 +539,7 @@ func (s *simplePhiState) lookupVarOutgoing(b *ssa.Block, t *types.Type, var_ ir.
                }
        }
        // Generate a FwdRef for the variable and return that.
-       v := b.NewValue0A(line, ssa.OpFwdRef, t, var_)
+       v := b.NewValue0A(line, ssa.OpFwdRef, t, FwdRefAux{N: var_})
        s.defvars[b.ID][var_] = v
        s.s.addNamedValue(var_, v)
        s.fwdrefs = append(s.fwdrefs, v)

diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go
index 2378ea7711b9526b3f3d00af7bc996ace3656b7d..90c754604299c528407d3cb5e9475eed7a5b187c 100644 (file)
--- a/src/cmd/compile/internal/gc/ssa.go
+++ b/src/cmd/compile/internal/gc/ssa.go
@@ -6051,7 +6051,7 @@ func (s *state) variable(name ir.Node, t *types.Type) *ssa.Value {
        }
        // Make a FwdRef, which records a value that's live on block input.
        // We'll find the matching definition as part of insertPhis.
-       v = s.newValue0A(ssa.OpFwdRef, t, name)
+       v = s.newValue0A(ssa.OpFwdRef, t, FwdRefAux{N: name})
        s.fwdVars[name] = v
        s.addNamedValue(name, v)
        return v