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cmd/compile: fix incorrect block for s390x Select1 op

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When inserting Select0 and Select1 ops we need to ensure that they
live in the same block as their argument. This is because they need
to be scheduled immediately after their argument for register and
flag allocation to work correctly.

Fixes #38356.

Change-Id: Iba384dbe87010f1c7c4ce909f08011e5f1de7fd5
Reviewed-on: https://go-review.googlesource.com/c/go/+/227879
Run-TryBot: Michael Munday <mike.munday@ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Michael Munday 2020-04-12 10:45:24 +01:00
parent 33ff63da4e
commit 334d410ae3
3 changed files with 75 additions and 8 deletions
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15
src/cmd/compile/internal/ssa/gen/S390X.rules
View File

@ -1218,10 +1218,17 @@
(FCMP (FMOVDconst [c]) x) && auxTo64F(c) == 0 -> (InvertFlags (LTDBR <v.Type> x))
(FCMPS (FMOVSconst [c]) x) && auxTo32F(c) == 0 -> (InvertFlags (LTEBR <v.Type> x))
// FSUB, FSUBS, FADD, FADDS now produce a flag, so when a comparison against zero instruction (e.g: LTDBR) is following
// one of those instructions, we can use the generated flag and remove the comparison instruction.
(LTDBR (Select0 x:(F(ADD|SUB) _ _))) -> (Select1 x)
(LTEBR (Select0 x:(F(ADDS|SUBS) _ _))) -> (Select1 x)
// FSUB, FSUBS, FADD, FADDS now produce a condition code representing the
// comparison of the result with 0.0. If a compare with zero instruction
// (e.g. LTDBR) is following one of those instructions, we can use the
// generated flag and remove the comparison instruction.
// Note: when inserting Select1 ops we need to ensure they are in the
// same block as their argument. We could also use @x.Block for this
// but moving the flag generating value to a different block seems to
// increase the likelihood that the flags value will have to be regenerated
// by flagalloc which is not what we want.
(LTDBR (Select0 x:(F(ADD|SUB) _ _))) && b == x.Block -> (Select1 x)
(LTEBR (Select0 x:(F(ADDS|SUBS) _ _))) && b == x.Block -> (Select1 x)
// Fold memory operations into operations.
// Exclude global data (SB) because these instructions cannot handle relative addresses.

14
src/cmd/compile/internal/ssa/rewriteS390X.go
View File

@ -8196,14 +8196,16 @@ func rewriteValueS390X_OpS390XLOCGR(v *Value) bool {
}
func rewriteValueS390X_OpS390XLTDBR(v *Value) bool {
v_0 := v.Args[0]
b := v.Block
// match: (LTDBR (Select0 x:(FADD _ _)))
// cond: b == x.Block
// result: (Select1 x)
for {
if v_0.Op != OpSelect0 {
break
}
x := v_0.Args[0]
if x.Op != OpS390XFADD {
if x.Op != OpS390XFADD || !(b == x.Block) {
break
}
v.reset(OpSelect1)
@ -8211,13 +8213,14 @@ func rewriteValueS390X_OpS390XLTDBR(v *Value) bool {
return true
}
// match: (LTDBR (Select0 x:(FSUB _ _)))
// cond: b == x.Block
// result: (Select1 x)
for {
if v_0.Op != OpSelect0 {
break
}
x := v_0.Args[0]
if x.Op != OpS390XFSUB {
if x.Op != OpS390XFSUB || !(b == x.Block) {
break
}
v.reset(OpSelect1)
@ -8228,14 +8231,16 @@ func rewriteValueS390X_OpS390XLTDBR(v *Value) bool {
}
func rewriteValueS390X_OpS390XLTEBR(v *Value) bool {
v_0 := v.Args[0]
b := v.Block
// match: (LTEBR (Select0 x:(FADDS _ _)))
// cond: b == x.Block
// result: (Select1 x)
for {
if v_0.Op != OpSelect0 {
break
}
x := v_0.Args[0]
if x.Op != OpS390XFADDS {
if x.Op != OpS390XFADDS || !(b == x.Block) {
break
}
v.reset(OpSelect1)
@ -8243,13 +8248,14 @@ func rewriteValueS390X_OpS390XLTEBR(v *Value) bool {
return true
}
// match: (LTEBR (Select0 x:(FSUBS _ _)))
// cond: b == x.Block
// result: (Select1 x)
for {
if v_0.Op != OpSelect0 {
break
}
x := v_0.Args[0]
if x.Op != OpS390XFSUBS {
if x.Op != OpS390XFSUBS || !(b == x.Block) {
break
}
v.reset(OpSelect1)

54
test/fixedbugs/issue38356.go Normal file
View File

@ -0,0 +1,54 @@
// compile
// Copyright 2020 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Make sure floating point operations that generate flags
// are scheduled correctly on s390x.
package p
func f1(x, y float64, z int) float64 {
a := x + y // generate flags
if z == 0 { // create basic block that does not clobber flags
return a
}
if a > 0 { // use flags in different basic block
return y
}
return x
}
func f2(x, y float64, z int) float64 {
a := x - y // generate flags
if z == 0 { // create basic block that does not clobber flags
return a
}
if a > 0 { // use flags in different basic block
return y
}
return x
}
func f3(x, y float32, z int) float32 {
a := x + y // generate flags
if z == 0 { // create basic block that does not clobber flags
return a
}
if a > 0 { // use flags in different basic block
return y
}
return x
}
func f4(x, y float32, z int) float32 {
a := x - y // generate flags
if z == 0 { // create basic block that does not clobber flags
return a
}
if a > 0 { // use flags in different basic block
return y
}
return x
}