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[dev.ssa] cmd/compile/internal/ssa: fix sign extension + load combo

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Load-and-sign-extend opcodes were being generated in the
wrong block, leading to having more than one memory variable
live at once.  Fix the rules + add a test.

Change-Id: Iadf80e55ea901549c15c628ae295c2d0f1f64525
Reviewed-on: https://go-review.googlesource.com/14591
Reviewed-by: Todd Neal <todd@tneal.org>
Run-TryBot: Todd Neal <todd@tneal.org>
This commit is contained in:
Keith Randall 2015-09-15 09:02:07 -07:00
parent e3869a6b65
commit cde977c23c
4 changed files with 71 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
src/cmd/compile/internal/gc/testdata/loadstore_ssa.go vendored
View File

@ -57,10 +57,31 @@ func testStoreSize_ssa(p *uint16, q *uint16, v uint32) {
var failed = false
func testExtStore_ssa(p *byte, b bool) int {
switch {
}
x := *p
*p = 7
if b {
return int(x)
}
return 0
}
func testExtStore() {
const start = 8
var b byte = start
if got := testExtStore_ssa(&b, true); got != start {
fmt.Println("testExtStore failed. want =", start, ", got =", got)
failed = true
}
}
func main() {
testLoadStoreOrder()
testStoreSize()
testExtStore()
if failed {
panic("failed")

10
src/cmd/compile/internal/ssa/gen/AMD64.rules
View File

@ -474,8 +474,14 @@
(SETNE (InvertFlags x)) -> (SETNE x)
// sign extended loads
(MOVBQSX (MOVBload [off] {sym} ptr mem)) -> (MOVBQSXload [off] {sym} ptr mem)
(MOVBQZX (MOVBload [off] {sym} ptr mem)) -> (MOVBQZXload [off] {sym} ptr mem)
// Note: The combined instruction must end up in the same block
// as the original load. If not, we end up making a value with
// memory type live in two different blocks, which can lead to
// multiple memory values alive simultaneously.
// TODO: somehow have this rewrite rule put the new MOVBQSXload in
// v.Args[0].Block instead of in v.Block?
(MOVBQSX (MOVBload [off] {sym} ptr mem)) && b == v.Args[0].Block -> (MOVBQSXload [off] {sym} ptr mem)
(MOVBQZX (MOVBload [off] {sym} ptr mem)) && b == v.Args[0].Block -> (MOVBQZXload [off] {sym} ptr mem)
// TODO: more
// Don't extend before storing

28
src/cmd/compile/internal/ssa/regalloc.go
View File

@ -1046,5 +1046,33 @@ func (f *Func) live() [][][]ID {
break
}
}
// Make sure that there is only one live memory variable in each set.
// Ideally we should check this at every instructiom, but at every
// edge seems good enough for now.
isMem := make([]bool, f.NumValues())
for _, b := range f.Blocks {
for _, v := range b.Values {
isMem[v.ID] = v.Type.IsMemory()
}
}
for _, b := range f.Blocks {
for i, c := range b.Succs {
nmem := 0
for _, id := range live[b.ID][i] {
if isMem[id] {
nmem++
}
}
if nmem > 1 {
f.Fatalf("more than one mem live on edge %v->%v: %v", b, c, live[b.ID][i])
}
// TODO: figure out why we get nmem==0 occasionally.
//if nmem == 0 {
// f.Fatalf("no mem live on edge %v->%v: %v", b, c, live[b.ID][i])
//}
}
}
return live
}

22
src/cmd/compile/internal/ssa/rewriteAMD64.go
View File

@ -3939,16 +3939,19 @@ func rewriteValueAMD64(v *Value, config *Config) bool {
;
case OpAMD64MOVBQSX:
// match: (MOVBQSX (MOVBload [off] {sym} ptr mem))
// cond:
// cond: b == v.Args[0].Block
// result: (MOVBQSXload [off] {sym} ptr mem)
{
if v.Args[0].Op != OpAMD64MOVBload {
goto end9de452216bde3b2e2a2d01f43da1f78e
goto end4fcdab76af223d4a6b942b532ebf860b
}
off := v.Args[0].AuxInt
sym := v.Args[0].Aux
ptr := v.Args[0].Args[0]
mem := v.Args[0].Args[1]
if !(b == v.Args[0].Block) {
goto end4fcdab76af223d4a6b942b532ebf860b
}
v.Op = OpAMD64MOVBQSXload
v.AuxInt = 0
v.Aux = nil
@ -3959,21 +3962,24 @@ func rewriteValueAMD64(v *Value, config *Config) bool {
v.AddArg(mem)
return true
}
goto end9de452216bde3b2e2a2d01f43da1f78e
end9de452216bde3b2e2a2d01f43da1f78e:
goto end4fcdab76af223d4a6b942b532ebf860b
end4fcdab76af223d4a6b942b532ebf860b:
;
case OpAMD64MOVBQZX:
// match: (MOVBQZX (MOVBload [off] {sym} ptr mem))
// cond:
// cond: b == v.Args[0].Block
// result: (MOVBQZXload [off] {sym} ptr mem)
{
if v.Args[0].Op != OpAMD64MOVBload {
goto end573f4e6a6fe8032338b85fddd4d1bab4
goto endce35c966b0a38aa124a610e5616a220c
}
off := v.Args[0].AuxInt
sym := v.Args[0].Aux
ptr := v.Args[0].Args[0]
mem := v.Args[0].Args[1]
if !(b == v.Args[0].Block) {
goto endce35c966b0a38aa124a610e5616a220c
}
v.Op = OpAMD64MOVBQZXload
v.AuxInt = 0
v.Aux = nil
@ -3984,8 +3990,8 @@ func rewriteValueAMD64(v *Value, config *Config) bool {
v.AddArg(mem)
return true
}
goto end573f4e6a6fe8032338b85fddd4d1bab4
end573f4e6a6fe8032338b85fddd4d1bab4:
goto endce35c966b0a38aa124a610e5616a220c
endce35c966b0a38aa124a610e5616a220c:
;
case OpAMD64MOVBload:
// match: (MOVBload [off1] {sym} (ADDQconst [off2] ptr) mem)