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

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>

diff --git a/src/cmd/compile/internal/ssa/gen/S390XOps.go b/src/cmd/compile/internal/ssa/gen/S390XOps.go
index 283a0fa6b557c51f196c5f46f3b714b914bd5f0a..65460bf6f711f64db96e7a029e280349b39ef1c6 100644 (file)
--- a/src/cmd/compile/internal/ssa/gen/S390XOps.go
+++ b/src/cmd/compile/internal/ssa/gen/S390XOps.go
@@ -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

diff --git a/src/cmd/compile/internal/ssa/opGen.go b/src/cmd/compile/internal/ssa/opGen.go
index 46ca7936dc7fb150a1b5c5f9794e344bd8a5078c..bf48bff8f127a8302148fb0937f57abcf7356692 100644 (file)
--- a/src/cmd/compile/internal/ssa/opGen.go
+++ b/src/cmd/compile/internal/ssa/opGen.go
@@ -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,