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: propagate constants through math.Float{32,64}{,from}bits

Browse source 
This CL adds generic SSA rules to propagate constants through raw bits
conversions between floats and integers. This allows constants to
propagate through some math functions. For example, math.Copysign(0, -1)
is now constant folded to a load of -0.0.

Requires a fix to the ARM assembler which loaded -0.0 as +0.0.

Change-Id: I52649a4691077c7414f19d17bb599a6743c23ac2
Reviewed-on: https://go-review.googlesource.com/62250
Run-TryBot: Michael Munday <mike.munday@ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
This commit is contained in:
Michael Munday 2017-09-08 01:31:13 +01:00
parent 4439b21d0c
commit 9da29b687f
5 changed files with 181 additions and 8 deletions
Download patch file Download diff file Expand all files Collapse all files

113
src/cmd/compile/internal/ssa/rewritegeneric.go
View file

@ -172,7 +172,7 @@ func rewriteValuegeneric(v *Value) bool {
case OpLess8U:
return rewriteValuegeneric_OpLess8U_0(v)
case OpLoad:
return rewriteValuegeneric_OpLoad_0(v)
return rewriteValuegeneric_OpLoad_0(v) || rewriteValuegeneric_OpLoad_10(v)
case OpLsh16x16:
return rewriteValuegeneric_OpLsh16x16_0(v)
case OpLsh16x32:
@ -11663,6 +11663,110 @@ func rewriteValuegeneric_OpLoad_0(v *Value) bool {
v.AddArg(x)
return true
}
// match: (Load <t1> p1 (Store {t2} p2 (Const64 [x]) _))
// cond: isSamePtr(p1,p2) && t2.(*types.Type).Size() == 8 && is64BitFloat(t1)
// result: (Const64F [x])
for {
t1 := v.Type
_ = v.Args[1]
p1 := v.Args[0]
v_1 := v.Args[1]
if v_1.Op != OpStore {
break
}
t2 := v_1.Aux
_ = v_1.Args[2]
p2 := v_1.Args[0]
v_1_1 := v_1.Args[1]
if v_1_1.Op != OpConst64 {
break
}
x := v_1_1.AuxInt
if !(isSamePtr(p1, p2) && t2.(*types.Type).Size() == 8 && is64BitFloat(t1)) {
break
}
v.reset(OpConst64F)
v.AuxInt = x
return true
}
// match: (Load <t1> p1 (Store {t2} p2 (Const32 [x]) _))
// cond: isSamePtr(p1,p2) && t2.(*types.Type).Size() == 4 && is32BitFloat(t1)
// result: (Const32F [f2i(float64(math.Float32frombits(uint32(x))))])
for {
t1 := v.Type
_ = v.Args[1]
p1 := v.Args[0]
v_1 := v.Args[1]
if v_1.Op != OpStore {
break
}
t2 := v_1.Aux
_ = v_1.Args[2]
p2 := v_1.Args[0]
v_1_1 := v_1.Args[1]
if v_1_1.Op != OpConst32 {
break
}
x := v_1_1.AuxInt
if !(isSamePtr(p1, p2) && t2.(*types.Type).Size() == 4 && is32BitFloat(t1)) {
break
}
v.reset(OpConst32F)
v.AuxInt = f2i(float64(math.Float32frombits(uint32(x))))
return true
}
// match: (Load <t1> p1 (Store {t2} p2 (Const64F [x]) _))
// cond: isSamePtr(p1,p2) && t2.(*types.Type).Size() == 8 && is64BitInt(t1)
// result: (Const64 [x])
for {
t1 := v.Type
_ = v.Args[1]
p1 := v.Args[0]
v_1 := v.Args[1]
if v_1.Op != OpStore {
break
}
t2 := v_1.Aux
_ = v_1.Args[2]
p2 := v_1.Args[0]
v_1_1 := v_1.Args[1]
if v_1_1.Op != OpConst64F {
break
}
x := v_1_1.AuxInt
if !(isSamePtr(p1, p2) && t2.(*types.Type).Size() == 8 && is64BitInt(t1)) {
break
}
v.reset(OpConst64)
v.AuxInt = x
return true
}
// match: (Load <t1> p1 (Store {t2} p2 (Const32F [x]) _))
// cond: isSamePtr(p1,p2) && t2.(*types.Type).Size() == 4 && is32BitInt(t1)
// result: (Const32 [int64(int32(math.Float32bits(float32(i2f(x)))))])
for {
t1 := v.Type
_ = v.Args[1]
p1 := v.Args[0]
v_1 := v.Args[1]
if v_1.Op != OpStore {
break
}
t2 := v_1.Aux
_ = v_1.Args[2]
p2 := v_1.Args[0]
v_1_1 := v_1.Args[1]
if v_1_1.Op != OpConst32F {
break
}
x := v_1_1.AuxInt
if !(isSamePtr(p1, p2) && t2.(*types.Type).Size() == 4 && is32BitInt(t1)) {
break
}
v.reset(OpConst32)
v.AuxInt = int64(int32(math.Float32bits(float32(i2f(x)))))
return true
}
// match: (Load <t> _ _)
// cond: t.IsStruct() && t.NumFields() == 0 && fe.CanSSA(t)
// result: (StructMake0)
@ -11801,6 +11905,13 @@ func rewriteValuegeneric_OpLoad_0(v *Value) bool {
v.AddArg(v6)
return true
}
return false
}
func rewriteValuegeneric_OpLoad_10(v *Value) bool {
b := v.Block
_ = b
fe := b.Func.fe
_ = fe
// match: (Load <t> _ _)
// cond: t.IsArray() && t.NumElem() == 0
// result: (ArrayMake0)