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cmd/compile: remove zeroing after newobject

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The Zero op right after newobject has been removed. But this rule
does not cover Store of constant zero (for SSA-able types). Add
rules to cover Store op as well.

Updates #19027.

Change-Id: I5d2b62eeca0aa9ce8dc7205b264b779de01c660b
Reviewed-on: https://go-review.googlesource.com/36836
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Cherry Zhang 2017-02-03 16:18:01 -05:00
parent 9b480521d8
commit c8eaeb8cba
3 changed files with 86 additions and 0 deletions
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12
src/cmd/compile/internal/ssa/gen/generic.rules
View File

@ -1390,6 +1390,18 @@
&& isSameSym(mem.Aux, "runtime.newobject")
&& c == config.ctxt.FixedFrameSize() + config.RegSize // offset of return value
-> mem
(Store (Load (OffPtr [c] (SP)) mem) x mem)
&& isConstZero(x)
&& mem.Op == OpStaticCall
&& isSameSym(mem.Aux, "runtime.newobject")
&& c == config.ctxt.FixedFrameSize() + config.RegSize // offset of return value
-> mem
(Store (OffPtr (Load (OffPtr [c] (SP)) mem)) x mem)
&& isConstZero(x)
&& mem.Op == OpStaticCall
&& isSameSym(mem.Aux, "runtime.newobject")
&& c == config.ctxt.FixedFrameSize() + config.RegSize // offset of return value
-> mem
// nil checks just need to rewrite to something useless.
// they will be deadcode eliminated soon afterwards.
(NilCheck (Load (OffPtr [c] (SP)) mem) mem)

10
src/cmd/compile/internal/ssa/rewrite.go
View File

@ -541,3 +541,13 @@ func experiment(f *Func) bool {
}
return r
}
func isConstZero(v *Value) bool {
switch v.Op {
case OpConstNil:
return true
case OpConst64, OpConst32, OpConst16, OpConst8, OpConstBool, OpConst32F, OpConst64F:
return v.AuxInt == 0
}
return false
}

64
src/cmd/compile/internal/ssa/rewritegeneric.go
View File

@ -14668,6 +14668,70 @@ func rewriteValuegeneric_OpStore(v *Value, config *Config) bool {
v.AddArg(mem)
return true
}
// match: (Store (Load (OffPtr [c] (SP)) mem) x mem)
// cond: isConstZero(x) && mem.Op == OpStaticCall && isSameSym(mem.Aux, "runtime.newobject") && c == config.ctxt.FixedFrameSize() + config.RegSize
// result: mem
for {
v_0 := v.Args[0]
if v_0.Op != OpLoad {
break
}
v_0_0 := v_0.Args[0]
if v_0_0.Op != OpOffPtr {
break
}
c := v_0_0.AuxInt
v_0_0_0 := v_0_0.Args[0]
if v_0_0_0.Op != OpSP {
break
}
mem := v_0.Args[1]
x := v.Args[1]
if mem != v.Args[2] {
break
}
if !(isConstZero(x) && mem.Op == OpStaticCall && isSameSym(mem.Aux, "runtime.newobject") && c == config.ctxt.FixedFrameSize()+config.RegSize) {
break
}
v.reset(OpCopy)
v.Type = mem.Type
v.AddArg(mem)
return true
}
// match: (Store (OffPtr (Load (OffPtr [c] (SP)) mem)) x mem)
// cond: isConstZero(x) && mem.Op == OpStaticCall && isSameSym(mem.Aux, "runtime.newobject") && c == config.ctxt.FixedFrameSize() + config.RegSize
// result: mem
for {
v_0 := v.Args[0]
if v_0.Op != OpOffPtr {
break
}
v_0_0 := v_0.Args[0]
if v_0_0.Op != OpLoad {
break
}
v_0_0_0 := v_0_0.Args[0]
if v_0_0_0.Op != OpOffPtr {
break
}
c := v_0_0_0.AuxInt
v_0_0_0_0 := v_0_0_0.Args[0]
if v_0_0_0_0.Op != OpSP {
break
}
mem := v_0_0.Args[1]
x := v.Args[1]
if mem != v.Args[2] {
break
}
if !(isConstZero(x) && mem.Op == OpStaticCall && isSameSym(mem.Aux, "runtime.newobject") && c == config.ctxt.FixedFrameSize()+config.RegSize) {
break
}
v.reset(OpCopy)
v.Type = mem.Type
v.AddArg(mem)
return true
}
return false
}
func rewriteValuegeneric_OpStringLen(v *Value, config *Config) bool {