Stowage/go
2
0
Fork 0
mirror of https://github.com/golang/go.git synced 2025-12-08 06:10:04 +00:00
Code Issues Projects Releases Packages Wiki Activity

cmd/compile/internal/ssa: simplify nil checks in opt.

Browse source 
* Simplify the nilcheck generated by
for _, e := range a {}
* No effect on the generated code because these nil checks
don't end up in the generated code.
* Useful for other analysis, e.g. it'll remove one dependecy
on the induction variable.

Change-Id: I6ee66ddfdc010ae22aea8dca48163303d93de7a9
Reviewed-on: https://go-review.googlesource.com/20307
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Alexandru Moșoi 2016-03-07 19:29:15 +01:00 • committed by Alexandru Moșoi
parent e806cd9f95
commit fb2f99d5fd
2 changed files with 39 additions and 0 deletions
Download patch file Download diff file Expand all files Collapse all files

35
src/cmd/compile/internal/ssa/rewritegeneric.go
View file

@ -206,6 +206,8 @@ func rewriteValuegeneric(v *Value, config *Config) bool {
return rewriteValuegeneric_OpNeqPtr(v, config)
case OpNeqSlice:
return rewriteValuegeneric_OpNeqSlice(v, config)
case OpNilCheck:
return rewriteValuegeneric_OpNilCheck(v, config)
case OpOffPtr:
return rewriteValuegeneric_OpOffPtr(v, config)
case OpOr16:
@ -4823,6 +4825,39 @@ func rewriteValuegeneric_OpNeqSlice(v *Value, config *Config) bool {
}
return false
}
func rewriteValuegeneric_OpNilCheck(v *Value, config *Config) bool {
b := v.Block
_ = b
// match: (NilCheck (Phi x (Add64 (Const64 [c]) y)) mem)
// cond: c > 0 && v.Args[0] == y
// result: (NilCheck x mem)
for {
if v.Args[0].Op != OpPhi {
break
}
x := v.Args[0].Args[0]
if v.Args[0].Args[1].Op != OpAdd64 {
break
}
if v.Args[0].Args[1].Args[0].Op != OpConst64 {
break
}
c := v.Args[0].Args[1].Args[0].AuxInt
y := v.Args[0].Args[1].Args[1]
if len(v.Args[0].Args) != 2 {
break
}
mem := v.Args[1]
if !(c > 0 && v.Args[0] == y) {
break
}
v.reset(OpNilCheck)
v.AddArg(x)
v.AddArg(mem)
return true
}
return false
}
func rewriteValuegeneric_OpOffPtr(v *Value, config *Config) bool {
b := v.Block
_ = b