[dev.ssa] cmd/compile : replace load of store with a copy
Loads of stores from the same pointer with compatible types
can be replaced with a copy.
Change-Id: I514b3ed8e5b6a9c432946880eac67a51b1607932
Reviewed-on: https://go-review.googlesource.com/19743
Run-TryBot: Todd Neal <todd@tneal.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
diff --git a/src/cmd/compile/internal/ssa/rewritegeneric.go b/src/cmd/compile/internal/ssa/rewritegeneric.go
index ae36112..7916c6d 100644
--- a/src/cmd/compile/internal/ssa/rewritegeneric.go
+++ b/src/cmd/compile/internal/ssa/rewritegeneric.go
@@ -2901,6 +2901,26 @@
func rewriteValuegeneric_OpLoad(v *Value, config *Config) bool {
b := v.Block
_ = b
+ // match: (Load <t1> p1 (Store [w] p2 x _))
+ // cond: isSamePtr(p1,p2) && t1.Compare(x.Type)==CMPeq && w == t1.Size()
+ // result: x
+ for {
+ t1 := v.Type
+ p1 := v.Args[0]
+ if v.Args[1].Op != OpStore {
+ break
+ }
+ w := v.Args[1].AuxInt
+ p2 := v.Args[1].Args[0]
+ x := v.Args[1].Args[1]
+ if !(isSamePtr(p1, p2) && t1.Compare(x.Type) == CMPeq && w == t1.Size()) {
+ break
+ }
+ v.reset(OpCopy)
+ v.Type = x.Type
+ v.AddArg(x)
+ return true
+ }
// match: (Load <t> _ _)
// cond: t.IsStruct() && t.NumFields() == 0 && config.fe.CanSSA(t)
// result: (StructMake0)
