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cmd/compile: fix load combining from a non-zero pointer offset

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When the pointer offset is non-zero in the small loads, we need to add the offset
when converting to the larger load.

Fixes #14694

Change-Id: I5ba8bcb3b9ce26c7fae0c4951500b9ef0fed54cd
Reviewed-on: https://go-review.googlesource.com/20333
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Todd Neal 2016-03-07 18:43:05 -06:00 committed by Todd Neal
parent 6df8038768
commit 481fe59012
3 changed files with 53 additions and 9 deletions
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35
src/cmd/compile/internal/gc/testdata/arith_ssa.go vendored
View File

@ -14,6 +14,40 @@ const (
y = 0x0fffFFFF
)
//go:noinline
func parseLE64(b []byte) uint64 {
// skip the first two bytes, and parse the remaining 8 as a uint64
return uint64(b[2]) | uint64(b[3])<<8 | uint64(b[4])<<16 | uint64(b[5])<<24 |
uint64(b[6])<<32 | uint64(b[7])<<40 | uint64(b[8])<<48 | uint64(b[9])<<56
}
//go:noinline
func parseLE32(b []byte) uint32 {
return uint32(b[2]) | uint32(b[3])<<8 | uint32(b[4])<<16 | uint32(b[5])<<24
}
//go:noinline
func parseLE16(b []byte) uint16 {
return uint16(b[2]) | uint16(b[3])<<8
}
// testLoadCombine tests for issue #14694 where load combining didn't respect the pointer offset.
func testLoadCombine() {
testData := []byte{0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09}
if want, got := uint64(0x0908070605040302), parseLE64(testData); want != got {
println("testLargeConst add failed, wanted", want, "got", got)
failed = true
}
if want, got := uint32(0x05040302), parseLE32(testData); want != got {
println("testLargeConst add failed, wanted", want, "got", got)
failed = true
}
if want, got := uint16(0x0302), parseLE16(testData); want != got {
println("testLargeConst add failed, wanted", want, "got", got)
failed = true
}
}
//go:noinline
func invalidAdd_ssa(x uint32) uint32 {
return x + y + y + y + y + y + y + y + y + y + y + y + y + y + y + y + y + y
@ -431,6 +465,7 @@ func main() {
testArithConstShift()
testArithRshConst()
testLargeConst()
testLoadCombine()
if failed {
panic("failed")

6
src/cmd/compile/internal/ssa/gen/AMD64.rules
View File

@ -1167,13 +1167,13 @@
// There are many ways these combinations could occur. This is
// designed to match the way encoding/binary.LittleEndian does it.
(ORW (MOVBQZXload [i] {s} p mem)
(SHLWconst [8] (MOVBQZXload [i+1] {s} p mem))) -> (MOVWload p mem)
(SHLWconst [8] (MOVBQZXload [i+1] {s} p mem))) -> (MOVWload (ADDQconst [i] p) mem)
(ORL (ORL (ORL
(MOVBQZXload [i] {s} p mem)
(SHLLconst [8] (MOVBQZXload [i+1] {s} p mem)))
(SHLLconst [16] (MOVBQZXload [i+2] {s} p mem)))
(SHLLconst [24] (MOVBQZXload [i+3] {s} p mem))) -> (MOVLload p mem)
(SHLLconst [24] (MOVBQZXload [i+3] {s} p mem))) -> (MOVLload (ADDQconst [i] p) mem)
(ORQ (ORQ (ORQ (ORQ (ORQ (ORQ (ORQ
(MOVBQZXload [i] {s} p mem)
@ -1183,4 +1183,4 @@
(SHLQconst [32] (MOVBQZXload [i+4] {s} p mem)))
(SHLQconst [40] (MOVBQZXload [i+5] {s} p mem)))
(SHLQconst [48] (MOVBQZXload [i+6] {s} p mem)))
(SHLQconst [56] (MOVBQZXload [i+7] {s} p mem))) -> (MOVQload p mem)
(SHLQconst [56] (MOVBQZXload [i+7] {s} p mem))) -> (MOVQload (ADDQconst [i] p) mem)

21
src/cmd/compile/internal/ssa/rewriteAMD64.go
View File

@ -9465,7 +9465,7 @@ func rewriteValueAMD64_OpAMD64ORL(v *Value, config *Config) bool {
}
// match: (ORL (ORL (ORL (MOVBQZXload [i] {s} p mem) (SHLLconst [8] (MOVBQZXload [i+1] {s} p mem))) (SHLLconst [16] (MOVBQZXload [i+2] {s} p mem))) (SHLLconst [24] (MOVBQZXload [i+3] {s} p mem)))
// cond:
// result: (MOVLload p mem)
// result: (MOVLload (ADDQconst [i] p) mem)
for {
if v.Args[0].Op != OpAMD64ORL {
break
@ -9544,7 +9544,10 @@ func rewriteValueAMD64_OpAMD64ORL(v *Value, config *Config) bool {
break
}
v.reset(OpAMD64MOVLload)
v.AddArg(p)
v0 := b.NewValue0(v.Line, OpAMD64ADDQconst, config.fe.TypeUInt64())
v0.AuxInt = i
v0.AddArg(p)
v.AddArg(v0)
v.AddArg(mem)
return true
}
@ -9646,7 +9649,7 @@ func rewriteValueAMD64_OpAMD64ORQ(v *Value, config *Config) bool {
}
// match: (ORQ (ORQ (ORQ (ORQ (ORQ (ORQ (ORQ (MOVBQZXload [i] {s} p mem) (SHLQconst [8] (MOVBQZXload [i+1] {s} p mem))) (SHLQconst [16] (MOVBQZXload [i+2] {s} p mem))) (SHLQconst [24] (MOVBQZXload [i+3] {s} p mem))) (SHLQconst [32] (MOVBQZXload [i+4] {s} p mem))) (SHLQconst [40] (MOVBQZXload [i+5] {s} p mem))) (SHLQconst [48] (MOVBQZXload [i+6] {s} p mem))) (SHLQconst [56] (MOVBQZXload [i+7] {s} p mem)))
// cond:
// result: (MOVQload p mem)
// result: (MOVQload (ADDQconst [i] p) mem)
for {
if v.Args[0].Op != OpAMD64ORQ {
break
@ -9821,7 +9824,10 @@ func rewriteValueAMD64_OpAMD64ORQ(v *Value, config *Config) bool {
break
}
v.reset(OpAMD64MOVQload)
v.AddArg(p)
v0 := b.NewValue0(v.Line, OpAMD64ADDQconst, config.fe.TypeUInt64())
v0.AuxInt = i
v0.AddArg(p)
v.AddArg(v0)
v.AddArg(mem)
return true
}
@ -9915,7 +9921,7 @@ func rewriteValueAMD64_OpAMD64ORW(v *Value, config *Config) bool {
}
// match: (ORW (MOVBQZXload [i] {s} p mem) (SHLWconst [8] (MOVBQZXload [i+1] {s} p mem)))
// cond:
// result: (MOVWload p mem)
// result: (MOVWload (ADDQconst [i] p) mem)
for {
if v.Args[0].Op != OpAMD64MOVBQZXload {
break
@ -9946,7 +9952,10 @@ func rewriteValueAMD64_OpAMD64ORW(v *Value, config *Config) bool {
break
}
v.reset(OpAMD64MOVWload)
v.AddArg(p)
v0 := b.NewValue0(v.Line, OpAMD64ADDQconst, config.fe.TypeUInt64())
v0.AuxInt = i
v0.AddArg(p)
v.AddArg(v0)
v.AddArg(mem)
return true
}