[dev.ssa] cmd/compile/internal/ssa: distribute multiplication into addition
* This is a very basic form of straight line strength reduction.
* Removes one multiplication from a[b].c++; a[b+1].c++
* It increases pressure on the register allocator because
CSE creates more copies of the multiplication sizeof(a[0])*b.
Change-Id: I686a18e9c24cc6f8bdfa925713afed034f7d36d0
Reviewed-on: https://go-review.googlesource.com/20091
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>
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 4f29cf5..0c71b2c 100644
--- a/src/cmd/compile/internal/ssa/rewritegeneric.go
+++ b/src/cmd/compile/internal/ssa/rewritegeneric.go
@@ -4044,6 +4044,41 @@
v.AddArg(x)
return true
}
+ // match: (Mul32 (Const32 <t> [c]) (Add32 <t> (Const32 <t> [d]) x))
+ // cond:
+ // result: (Add32 (Const32 <t> [c*d]) (Mul32 <t> (Const32 <t> [c]) x))
+ for {
+ if v.Args[0].Op != OpConst32 {
+ break
+ }
+ t := v.Args[0].Type
+ c := v.Args[0].AuxInt
+ if v.Args[1].Op != OpAdd32 {
+ break
+ }
+ if v.Args[1].Type != v.Args[0].Type {
+ break
+ }
+ if v.Args[1].Args[0].Op != OpConst32 {
+ break
+ }
+ if v.Args[1].Args[0].Type != v.Args[0].Type {
+ break
+ }
+ d := v.Args[1].Args[0].AuxInt
+ x := v.Args[1].Args[1]
+ v.reset(OpAdd32)
+ v0 := b.NewValue0(v.Line, OpConst32, t)
+ v0.AuxInt = c * d
+ v.AddArg(v0)
+ v1 := b.NewValue0(v.Line, OpMul32, t)
+ v2 := b.NewValue0(v.Line, OpConst32, t)
+ v2.AuxInt = c
+ v1.AddArg(v2)
+ v1.AddArg(x)
+ v.AddArg(v1)
+ return true
+ }
// match: (Mul32 (Const32 [0]) _)
// cond:
// result: (Const32 [0])
@@ -4099,6 +4134,41 @@
v.AddArg(x)
return true
}
+ // match: (Mul64 (Const64 <t> [c]) (Add64 <t> (Const64 <t> [d]) x))
+ // cond:
+ // result: (Add64 (Const64 <t> [c*d]) (Mul64 <t> (Const64 <t> [c]) x))
+ for {
+ if v.Args[0].Op != OpConst64 {
+ break
+ }
+ t := v.Args[0].Type
+ c := v.Args[0].AuxInt
+ if v.Args[1].Op != OpAdd64 {
+ break
+ }
+ if v.Args[1].Type != v.Args[0].Type {
+ break
+ }
+ if v.Args[1].Args[0].Op != OpConst64 {
+ break
+ }
+ if v.Args[1].Args[0].Type != v.Args[0].Type {
+ break
+ }
+ d := v.Args[1].Args[0].AuxInt
+ x := v.Args[1].Args[1]
+ v.reset(OpAdd64)
+ v0 := b.NewValue0(v.Line, OpConst64, t)
+ v0.AuxInt = c * d
+ v.AddArg(v0)
+ v1 := b.NewValue0(v.Line, OpMul64, t)
+ v2 := b.NewValue0(v.Line, OpConst64, t)
+ v2.AuxInt = c
+ v1.AddArg(v2)
+ v1.AddArg(x)
+ v.AddArg(v1)
+ return true
+ }
// match: (Mul64 (Const64 [0]) _)
// cond:
// result: (Const64 [0])
