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[dev.ssa] cmd/compile/ssa: eliminate Zero with dse

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Consider OpZero to be a store so it can be eliminated by dse.

Change-Id: Idebb6a190657b76966f0c5b20f2ec9f52fe47499
Reviewed-on: https://go-review.googlesource.com/13447
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Todd Neal 2015-08-10 21:05:35 -05:00
parent 463858e6ff
commit dee1f2750b
2 changed files with 28 additions and 10 deletions
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20
src/cmd/compile/internal/ssa/deadstore.go
View File

@ -30,7 +30,7 @@ func dse(f *Func) {
for _, a := range v.Args {
if a.Block == b && a.Type.IsMemory() {
storeUse.add(a.ID)
if v.Op != OpStore {
if v.Op != OpStore && v.Op != OpZero {
// CALL, DUFFCOPY, etc. are both
// reads and writes.
loadUse.add(a.ID)
@ -77,12 +77,24 @@ func dse(f *Func) {
// Clear all shadowed addresses.
shadowed.clear()
}
if v.Op == OpStore {
if v.Op == OpStore || v.Op == OpZero {
if shadowed.contains(v.Args[0].ID) {
// Modify store into a copy
v.Op = OpCopy
if v.Op == OpStore {
// store addr value mem
v.SetArgs1(v.Args[2])
} else {
// zero addr mem
sz := v.Args[0].Type.Elem().Size()
if v.AuxInt != sz {
f.Fatalf("mismatched zero/store sizes: %d and %d [%s]",
v.AuxInt, sz, v.LongString())
}
v.SetArgs1(v.Args[1])
}
v.Aux = nil
v.SetArgs1(v.Args[2])
v.AuxInt = 0
v.Op = OpCopy
} else {
shadowed.add(v.Args[0].ID)
}

18
src/cmd/compile/internal/ssa/deadstore_test.go
View File

@ -4,9 +4,7 @@
package ssa
import (
"testing"
)
import "testing"
func TestDeadStore(t *testing.T) {
c := testConfig(t)
@ -18,9 +16,12 @@ func TestDeadStore(t *testing.T) {
Valu("v", OpConstBool, TypeBool, 0, true),
Valu("addr1", OpAddr, ptrType, 0, nil, "sb"),
Valu("addr2", OpAddr, ptrType, 0, nil, "sb"),
Valu("store1", OpStore, TypeMem, 0, nil, "addr1", "v", "start"),
Valu("addr3", OpAddr, ptrType, 0, nil, "sb"),
Valu("zero1", OpZero, TypeMem, 8, nil, "addr3", "start"),
Valu("store1", OpStore, TypeMem, 0, nil, "addr1", "v", "zero1"),
Valu("store2", OpStore, TypeMem, 0, nil, "addr2", "v", "store1"),
Valu("store3", OpStore, TypeMem, 0, nil, "addr1", "v", "store2"),
Valu("store4", OpStore, TypeMem, 0, nil, "addr3", "v", "store3"),
Goto("exit")),
Bloc("exit",
Exit("store3")))
@ -29,10 +30,15 @@ func TestDeadStore(t *testing.T) {
dse(fun.f)
CheckFunc(fun.f)
v := fun.values["store1"]
if v.Op != OpCopy {
v1 := fun.values["store1"]
if v1.Op != OpCopy {
t.Errorf("dead store not removed")
}
v2 := fun.values["zero1"]
if v2.Op != OpCopy {
t.Errorf("dead store (zero) not removed")
}
}
func TestDeadStorePhi(t *testing.T) {
// make sure we don't get into an infinite loop with phi values.