[release-branch.go1.14] cmd/compile: mark s390x int <-> float conversions as clobbering flags

These conversion instructions set the condition code and so should
be marked as clobbering flags.

Updates #39651.
Fixes #39690.

Change-Id: I1e3f2cf33337128d321b52ac72f46d1b8798ebd9
Reviewed-on: https://go-review.googlesource.com/c/go/+/242237
Run-TryBot: Michael Munday <mike.munday@ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

3 files changed, 72 insertions, 36 deletions

diff --git a/src/cmd/compile/internal/ssa/gen/S390XOps.go b/src/cmd/compile/internal/ssa/gen/S390XOps.go
index 6517957fd4..62d56bf182 100644
--- a/src/cmd/compile/internal/ssa/gen/S390XOps.go
+++ b/src/cmd/compile/internal/ssa/gen/S390XOps.go
@@ -391,18 +391,20 @@ func init() {
 
 		{name: "MOVDconst", reg: gp01, asm: "MOVD", typ: "UInt64", aux: "Int64", rematerializeable: true}, // auxint
 
-		{name: "LDGR", argLength: 1, reg: gpfp, asm: "LDGR"},     // move int64 to float64 (no conversion)
-		{name: "LGDR", argLength: 1, reg: fpgp, asm: "LGDR"},     // move float64 to int64 (no conversion)
-		{name: "CFDBRA", argLength: 1, reg: fpgp, asm: "CFDBRA"}, // convert float64 to int32
-		{name: "CGDBRA", argLength: 1, reg: fpgp, asm: "CGDBRA"}, // convert float64 to int64
-		{name: "CFEBRA", argLength: 1, reg: fpgp, asm: "CFEBRA"}, // convert float32 to int32
-		{name: "CGEBRA", argLength: 1, reg: fpgp, asm: "CGEBRA"}, // convert float32 to int64
-		{name: "CEFBRA", argLength: 1, reg: gpfp, asm: "CEFBRA"}, // convert int32 to float32
-		{name: "CDFBRA", argLength: 1, reg: gpfp, asm: "CDFBRA"}, // convert int32 to float64
-		{name: "CEGBRA", argLength: 1, reg: gpfp, asm: "CEGBRA"}, // convert int64 to float32
-		{name: "CDGBRA", argLength: 1, reg: gpfp, asm: "CDGBRA"}, // convert int64 to float64
-		{name: "LEDBR", argLength: 1, reg: fp11, asm: "LEDBR"},   // convert float64 to float32
-		{name: "LDEBR", argLength: 1, reg: fp11, asm: "LDEBR"},   // convert float32 to float64
+		{name: "LDGR", argLength: 1, reg: gpfp, asm: "LDGR"}, // move int64 to float64 (no conversion)
+		{name: "LGDR", argLength: 1, reg: fpgp, asm: "LGDR"}, // move float64 to int64 (no conversion)
+
+		{name: "CFDBRA", argLength: 1, reg: fpgp, asm: "CFDBRA", clobberFlags: true}, // convert float64 to int32
+		{name: "CGDBRA", argLength: 1, reg: fpgp, asm: "CGDBRA", clobberFlags: true}, // convert float64 to int64
+		{name: "CFEBRA", argLength: 1, reg: fpgp, asm: "CFEBRA", clobberFlags: true}, // convert float32 to int32
+		{name: "CGEBRA", argLength: 1, reg: fpgp, asm: "CGEBRA", clobberFlags: true}, // convert float32 to int64
+		{name: "CEFBRA", argLength: 1, reg: gpfp, asm: "CEFBRA", clobberFlags: true}, // convert int32 to float32
+		{name: "CDFBRA", argLength: 1, reg: gpfp, asm: "CDFBRA", clobberFlags: true}, // convert int32 to float64
+		{name: "CEGBRA", argLength: 1, reg: gpfp, asm: "CEGBRA", clobberFlags: true}, // convert int64 to float32
+		{name: "CDGBRA", argLength: 1, reg: gpfp, asm: "CDGBRA", clobberFlags: true}, // convert int64 to float64
+
+		{name: "LEDBR", argLength: 1, reg: fp11, asm: "LEDBR"}, // convert float64 to float32
+		{name: "LDEBR", argLength: 1, reg: fp11, asm: "LDEBR"}, // convert float32 to float64
 
 		{name: "MOVDaddr", argLength: 1, reg: addr, aux: "SymOff", rematerializeable: true, symEffect: "Read"}, // arg0 + auxint + offset encoded in aux
 		{name: "MOVDaddridx", argLength: 2, reg: addridx, aux: "SymOff", symEffect: "Read"},                    // arg0 + arg1 + auxint + aux
diff --git a/src/cmd/compile/internal/ssa/opGen.go b/src/cmd/compile/internal/ssa/opGen.go
index 86428a3e84..dd05eecc93 100644
--- a/src/cmd/compile/internal/ssa/opGen.go
+++ b/src/cmd/compile/internal/ssa/opGen.go
@@ -28192,9 +28192,10 @@ var opcodeTable = [...]opInfo{
 		},
 	},
 	{
-		name:   "CFDBRA",
-		argLen: 1,
-		asm:    s390x.ACFDBRA,
+		name:         "CFDBRA",
+		argLen:       1,
+		clobberFlags: true,
+		asm:          s390x.ACFDBRA,
 		reg: regInfo{
 			inputs: []inputInfo{
 				{0, 4294901760}, // F0 F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 F13 F14 F15
@@ -28205,9 +28206,10 @@ var opcodeTable = [...]opInfo{
 		},
 	},
 	{
-		name:   "CGDBRA",
-		argLen: 1,
-		asm:    s390x.ACGDBRA,
+		name:         "CGDBRA",
+		argLen:       1,
+		clobberFlags: true,
+		asm:          s390x.ACGDBRA,
 		reg: regInfo{
 			inputs: []inputInfo{
 				{0, 4294901760}, // F0 F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 F13 F14 F15
@@ -28218,9 +28220,10 @@ var opcodeTable = [...]opInfo{
 		},
 	},
 	{
-		name:   "CFEBRA",
-		argLen: 1,
-		asm:    s390x.ACFEBRA,
+		name:         "CFEBRA",
+		argLen:       1,
+		clobberFlags: true,
+		asm:          s390x.ACFEBRA,
 		reg: regInfo{
 			inputs: []inputInfo{
 				{0, 4294901760}, // F0 F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 F13 F14 F15
@@ -28231,9 +28234,10 @@ var opcodeTable = [...]opInfo{
 		},
 	},
 	{
-		name:   "CGEBRA",
-		argLen: 1,
-		asm:    s390x.ACGEBRA,
+		name:         "CGEBRA",
+		argLen:       1,
+		clobberFlags: true,
+		asm:          s390x.ACGEBRA,
 		reg: regInfo{
 			inputs: []inputInfo{
 				{0, 4294901760}, // F0 F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 F13 F14 F15
@@ -28244,9 +28248,10 @@ var opcodeTable = [...]opInfo{
 		},
 	},
 	{
-		name:   "CEFBRA",
-		argLen: 1,
-		asm:    s390x.ACEFBRA,
+		name:         "CEFBRA",
+		argLen:       1,
+		clobberFlags: true,
+		asm:          s390x.ACEFBRA,
 		reg: regInfo{
 			inputs: []inputInfo{
 				{0, 23551}, // R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 R11 R12 R14
@@ -28257,9 +28262,10 @@ var opcodeTable = [...]opInfo{
 		},
 	},
 	{
-		name:   "CDFBRA",
-		argLen: 1,
-		asm:    s390x.ACDFBRA,
+		name:         "CDFBRA",
+		argLen:       1,
+		clobberFlags: true,
+		asm:          s390x.ACDFBRA,
 		reg: regInfo{
 			inputs: []inputInfo{
 				{0, 23551}, // R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 R11 R12 R14
@@ -28270,9 +28276,10 @@ var opcodeTable = [...]opInfo{
 		},
 	},
 	{
-		name:   "CEGBRA",
-		argLen: 1,
-		asm:    s390x.ACEGBRA,
+		name:         "CEGBRA",
+		argLen:       1,
+		clobberFlags: true,
+		asm:          s390x.ACEGBRA,
 		reg: regInfo{
 			inputs: []inputInfo{
 				{0, 23551}, // R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 R11 R12 R14
@@ -28283,9 +28290,10 @@ var opcodeTable = [...]opInfo{
 		},
 	},
 	{
-		name:   "CDGBRA",
-		argLen: 1,
-		asm:    s390x.ACDGBRA,
+		name:         "CDGBRA",
+		argLen:       1,
+		clobberFlags: true,
+		asm:          s390x.ACDGBRA,
 		reg: regInfo{
 			inputs: []inputInfo{
 				{0, 23551}, // R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 R11 R12 R14
diff --git a/test/fixedbugs/issue39651.go b/test/fixedbugs/issue39651.go
new file mode 100644
index 0000000000..256a34dcb3
--- /dev/null
+++ b/test/fixedbugs/issue39651.go
@@ -0,0 +1,26 @@
+// run
+
+// 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.
+
+// Test that float -> integer conversion doesn't clobber
+// flags.
+
+package main
+
+//go:noinline
+func f(x, y float64, a, b *bool, r *int64) {
+	*a = x < y    // set flags
+	*r = int64(x) // clobber flags
+	*b = x == y   // use flags
+}
+
+func main() {
+	var a, b bool
+	var r int64
+	f(1, 1, &a, &b, &r)
+	if a || !b {
+		panic("comparison incorrect")
+	}
+}