From: Michael Munday <mike.munday@ibm.com>
Date: Wed, 1 Apr 2020 10:21:03 +0000 (-0700)
Subject: cmd/compile: mark 'store multiple' as clobbering flags on s390x
X-Git-Tag: go1.15beta1~683
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=a7a0f0305035948f4c86e08e6e64409ab11a6f67;p=gostls13.git

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 283a0fa6b5..65460bf6f7 100644
--- 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 46ca7936dc..bf48bff8f1 100644
--- 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,