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cmd/compile: mark 'store multiple' as clobbering flags on s390x

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Store multiple instructions can clobber flags on s390x when the
offset passed into the assembler is outside the range representable
with a signed 20 bit integer. This is because the assembler uses
the agfi instruction to implement the large offset. The assembler
could use a different sequence of instructions, but for now just
mark the instruction as 'clobberFlags' since this is risk free.

Noticed while investigating #38195.

No test yet since I'm not sure how to get this bug to trigger and
I haven't seen it affect real code.

Change-Id: I4a6ab96455a3ef8ffacb76ef0166b97eb40ff925
Reviewed-on: https://go-review.googlesource.com/c/go/+/226759
Run-TryBot: Michael Munday <mike.munday@ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
This commit is contained in:
Michael Munday 2020-04-01 03:21:03 -07:00
parent 801cd7c84d
commit a7a0f03050
2 changed files with 12 additions and 0 deletions
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6
src/cmd/compile/internal/ssa/gen/S390XOps.go
View file

@ -630,6 +630,7 @@ func init() {
asm: "STMG",
faultOnNilArg0: true,
symEffect: "Write",
clobberFlags: true, // TODO(mundaym): currently uses AGFI to handle large offsets
},
{
name: "STMG3",
@ -640,6 +641,7 @@ func init() {
asm: "STMG",
faultOnNilArg0: true,
symEffect: "Write",
clobberFlags: true, // TODO(mundaym): currently uses AGFI to handle large offsets
},
{
name: "STMG4",
@ -657,6 +659,7 @@ func init() {
asm: "STMG",
faultOnNilArg0: true,
symEffect: "Write",
clobberFlags: true, // TODO(mundaym): currently uses AGFI to handle large offsets
},
{
name: "STM2",
@ -667,6 +670,7 @@ func init() {
asm: "STMY",
faultOnNilArg0: true,
symEffect: "Write",
clobberFlags: true, // TODO(mundaym): currently uses AGFI to handle large offsets
},
{
name: "STM3",
@ -677,6 +681,7 @@ func init() {
asm: "STMY",
faultOnNilArg0: true,
symEffect: "Write",
clobberFlags: true, // TODO(mundaym): currently uses AGFI to handle large offsets
},
{
name: "STM4",
@ -694,6 +699,7 @@ func init() {
asm: "STMY",
faultOnNilArg0: true,
symEffect: "Write",
clobberFlags: true, // TODO(mundaym): currently uses AGFI to handle large offsets
},
// large move

6
src/cmd/compile/internal/ssa/opGen.go
View file

@ -30110,6 +30110,7 @@ var opcodeTable = [...]opInfo{
name: "STMG2",
auxType: auxSymOff,
argLen: 4,
clobberFlags: true,
faultOnNilArg0: true,
symEffect: SymWrite,
asm: s390x.ASTMG,
@ -30125,6 +30126,7 @@ var opcodeTable = [...]opInfo{
name: "STMG3",
auxType: auxSymOff,
argLen: 5,
clobberFlags: true,
faultOnNilArg0: true,
symEffect: SymWrite,
asm: s390x.ASTMG,
@ -30141,6 +30143,7 @@ var opcodeTable = [...]opInfo{
name: "STMG4",
auxType: auxSymOff,
argLen: 6,
clobberFlags: true,
faultOnNilArg0: true,
symEffect: SymWrite,
asm: s390x.ASTMG,
@ -30158,6 +30161,7 @@ var opcodeTable = [...]opInfo{
name: "STM2",
auxType: auxSymOff,
argLen: 4,
clobberFlags: true,
faultOnNilArg0: true,
symEffect: SymWrite,
asm: s390x.ASTMY,
@ -30173,6 +30177,7 @@ var opcodeTable = [...]opInfo{
name: "STM3",
auxType: auxSymOff,
argLen: 5,
clobberFlags: true,
faultOnNilArg0: true,
symEffect: SymWrite,
asm: s390x.ASTMY,
@ -30189,6 +30194,7 @@ var opcodeTable = [...]opInfo{
name: "STM4",
auxType: auxSymOff,
argLen: 6,
clobberFlags: true,
faultOnNilArg0: true,
symEffect: SymWrite,
asm: s390x.ASTMY,