cmd/compile: mark architecture-specific unsafe points

Introduce a mechanism for marking architecture-specific Ops
unsafe. And mark ones that use REGTMP on ARM64, as for async
preemption we will be using REGTMP as a temporary register in the
injected call.

Change-Id: I8ff22e87d8f9cb10d02a2f0af7c12ad6d7d58f54
Reviewed-on: https://go-review.googlesource.com/c/go/+/203459
Run-TryBot: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Austin Clements <austin@google.com>

5 files changed, 32 insertions, 8 deletions

diff --git a/src/cmd/compile/internal/gc/plive.go b/src/cmd/compile/internal/gc/plive.go
index 5f0ece0ad7..d6ce9017e4 100644
--- a/src/cmd/compile/internal/gc/plive.go
+++ b/src/cmd/compile/internal/gc/plive.go
@@ -639,6 +639,15 @@ func (lv *Liveness) markUnsafePoints() {
 
 	lv.unsafePoints = bvalloc(int32(lv.f.NumValues()))
 
+	// Mark architecture-specific unsafe pointes.
+	for _, b := range lv.f.Blocks {
+		for _, v := range b.Values {
+			if v.Op.UnsafePoint() {
+				lv.unsafePoints.Set(int32(v.ID))
+			}
+		}
+	}
+
 	// Mark write barrier unsafe points.
 	for _, wbBlock := range lv.f.WBLoads {
 		if wbBlock.Kind == ssa.BlockPlain && len(wbBlock.Values) == 0 {
diff --git a/src/cmd/compile/internal/ssa/gen/ARM64Ops.go b/src/cmd/compile/internal/ssa/gen/ARM64Ops.go
index 59a6004b97..6fdb5729c5 100644
--- a/src/cmd/compile/internal/ssa/gen/ARM64Ops.go
+++ b/src/cmd/compile/internal/ssa/gen/ARM64Ops.go
@@ -620,8 +620,8 @@ func init() {
 		// LDAXR	(Rarg0), Rout
 		// STLXR	Rarg1, (Rarg0), Rtmp
 		// CBNZ		Rtmp, -2(PC)
-		{name: "LoweredAtomicExchange64", argLength: 3, reg: gpxchg, resultNotInArgs: true, faultOnNilArg0: true, hasSideEffects: true},
-		{name: "LoweredAtomicExchange32", argLength: 3, reg: gpxchg, resultNotInArgs: true, faultOnNilArg0: true, hasSideEffects: true},
+		{name: "LoweredAtomicExchange64", argLength: 3, reg: gpxchg, resultNotInArgs: true, faultOnNilArg0: true, hasSideEffects: true, unsafePoint: true},
+		{name: "LoweredAtomicExchange32", argLength: 3, reg: gpxchg, resultNotInArgs: true, faultOnNilArg0: true, hasSideEffects: true, unsafePoint: true},
 
 		// atomic add.
 		// *arg0 += arg1. arg2=mem. returns <new content of *arg0, memory>. auxint must be zero.
@@ -629,8 +629,8 @@ func init() {
 		// ADD		Rarg1, Rout
 		// STLXR	Rout, (Rarg0), Rtmp
 		// CBNZ		Rtmp, -3(PC)
-		{name: "LoweredAtomicAdd64", argLength: 3, reg: gpxchg, resultNotInArgs: true, faultOnNilArg0: true, hasSideEffects: true},
-		{name: "LoweredAtomicAdd32", argLength: 3, reg: gpxchg, resultNotInArgs: true, faultOnNilArg0: true, hasSideEffects: true},
+		{name: "LoweredAtomicAdd64", argLength: 3, reg: gpxchg, resultNotInArgs: true, faultOnNilArg0: true, hasSideEffects: true, unsafePoint: true},
+		{name: "LoweredAtomicAdd32", argLength: 3, reg: gpxchg, resultNotInArgs: true, faultOnNilArg0: true, hasSideEffects: true, unsafePoint: true},
 
 		// atomic add variant.
 		// *arg0 += arg1. arg2=mem. returns <new content of *arg0, memory>. auxint must be zero.
@@ -653,8 +653,8 @@ func init() {
 		// STLXR	Rarg2, (Rarg0), Rtmp
 		// CBNZ		Rtmp, -4(PC)
 		// CSET		EQ, Rout
-		{name: "LoweredAtomicCas64", argLength: 4, reg: gpcas, resultNotInArgs: true, clobberFlags: true, faultOnNilArg0: true, hasSideEffects: true},
-		{name: "LoweredAtomicCas32", argLength: 4, reg: gpcas, resultNotInArgs: true, clobberFlags: true, faultOnNilArg0: true, hasSideEffects: true},
+		{name: "LoweredAtomicCas64", argLength: 4, reg: gpcas, resultNotInArgs: true, clobberFlags: true, faultOnNilArg0: true, hasSideEffects: true, unsafePoint: true},
+		{name: "LoweredAtomicCas32", argLength: 4, reg: gpcas, resultNotInArgs: true, clobberFlags: true, faultOnNilArg0: true, hasSideEffects: true, unsafePoint: true},
 
 		// atomic and/or.
 		// *arg0 &= (|=) arg1. arg2=mem. returns <new content of *arg0, memory>. auxint must be zero.
@@ -662,8 +662,8 @@ func init() {
 		// AND/OR	Rarg1, Rout
 		// STLXRB	Rout, (Rarg0), Rtmp
 		// CBNZ		Rtmp, -3(PC)
-		{name: "LoweredAtomicAnd8", argLength: 3, reg: gpxchg, resultNotInArgs: true, asm: "AND", typ: "(UInt8,Mem)", faultOnNilArg0: true, hasSideEffects: true},
-		{name: "LoweredAtomicOr8", argLength: 3, reg: gpxchg, resultNotInArgs: true, asm: "ORR", typ: "(UInt8,Mem)", faultOnNilArg0: true, hasSideEffects: true},
+		{name: "LoweredAtomicAnd8", argLength: 3, reg: gpxchg, resultNotInArgs: true, asm: "AND", typ: "(UInt8,Mem)", faultOnNilArg0: true, hasSideEffects: true, unsafePoint: true},
+		{name: "LoweredAtomicOr8", argLength: 3, reg: gpxchg, resultNotInArgs: true, asm: "ORR", typ: "(UInt8,Mem)", faultOnNilArg0: true, hasSideEffects: true, unsafePoint: true},
 
 		// LoweredWB invokes runtime.gcWriteBarrier. arg0=destptr, arg1=srcptr, arg2=mem, aux=runtime.gcWriteBarrier
 		// It saves all GP registers if necessary,
diff --git a/src/cmd/compile/internal/ssa/gen/main.go b/src/cmd/compile/internal/ssa/gen/main.go
index 55ba338efa..2107da4f4e 100644
--- a/src/cmd/compile/internal/ssa/gen/main.go
+++ b/src/cmd/compile/internal/ssa/gen/main.go
@@ -63,6 +63,7 @@ type opData struct {
 	usesScratch       bool   // this op requires scratch memory space
 	hasSideEffects    bool   // for "reasons", not to be eliminated.  E.g., atomic store, #19182.
 	zeroWidth         bool   // op never translates into any machine code. example: copy, which may sometimes translate to machine code, is not zero-width.
+	unsafePoint       bool   // this op is an unsafe point, i.e. not safe for async preemption
 	symEffect         string // effect this op has on symbol in aux
 	scale             uint8  // amd64/386 indexed load scale
 }
@@ -325,6 +326,9 @@ func genOp() {
 			if v.zeroWidth {
 				fmt.Fprintln(w, "zeroWidth: true,")
 			}
+			if v.unsafePoint {
+				fmt.Fprintln(w, "unsafePoint: true,")
+			}
 			needEffect := strings.HasPrefix(v.aux, "Sym")
 			if v.symEffect != "" {
 				if !needEffect {
@@ -401,6 +405,7 @@ func genOp() {
 
 	fmt.Fprintln(w, "func (o Op) SymEffect() SymEffect { return opcodeTable[o].symEffect }")
 	fmt.Fprintln(w, "func (o Op) IsCall() bool { return opcodeTable[o].call }")
+	fmt.Fprintln(w, "func (o Op) UnsafePoint() bool { return opcodeTable[o].unsafePoint }")
 
 	// generate registers
 	for _, a := range archs {
diff --git a/src/cmd/compile/internal/ssa/op.go b/src/cmd/compile/internal/ssa/op.go
index 10534433a7..ec9e7863a0 100644
--- a/src/cmd/compile/internal/ssa/op.go
+++ b/src/cmd/compile/internal/ssa/op.go
@@ -36,6 +36,7 @@ type opInfo struct {
 	usesScratch       bool      // this op requires scratch memory space
 	hasSideEffects    bool      // for "reasons", not to be eliminated.  E.g., atomic store, #19182.
 	zeroWidth         bool      // op never translates into any machine code. example: copy, which may sometimes translate to machine code, is not zero-width.
+	unsafePoint       bool      // this op is an unsafe point, i.e. not safe for async preemption
 	symEffect         SymEffect // effect this op has on symbol in aux
 	scale             uint8     // amd64/386 indexed load scale
 }
diff --git a/src/cmd/compile/internal/ssa/opGen.go b/src/cmd/compile/internal/ssa/opGen.go
index 9f112c10f1..e9a709467e 100644
--- a/src/cmd/compile/internal/ssa/opGen.go
+++ b/src/cmd/compile/internal/ssa/opGen.go
@@ -18948,6 +18948,7 @@ var opcodeTable = [...]opInfo{
 		resultNotInArgs: true,
 		faultOnNilArg0:  true,
 		hasSideEffects:  true,
+		unsafePoint:     true,
 		reg: regInfo{
 			inputs: []inputInfo{
 				{1, 805044223},           // R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 R11 R12 R13 R14 R15 R16 R17 R19 R20 R21 R22 R23 R24 R25 R26 g R30
@@ -18964,6 +18965,7 @@ var opcodeTable = [...]opInfo{
 		resultNotInArgs: true,
 		faultOnNilArg0:  true,
 		hasSideEffects:  true,
+		unsafePoint:     true,
 		reg: regInfo{
 			inputs: []inputInfo{
 				{1, 805044223},           // R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 R11 R12 R13 R14 R15 R16 R17 R19 R20 R21 R22 R23 R24 R25 R26 g R30
@@ -18980,6 +18982,7 @@ var opcodeTable = [...]opInfo{
 		resultNotInArgs: true,
 		faultOnNilArg0:  true,
 		hasSideEffects:  true,
+		unsafePoint:     true,
 		reg: regInfo{
 			inputs: []inputInfo{
 				{1, 805044223},           // R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 R11 R12 R13 R14 R15 R16 R17 R19 R20 R21 R22 R23 R24 R25 R26 g R30
@@ -18996,6 +18999,7 @@ var opcodeTable = [...]opInfo{
 		resultNotInArgs: true,
 		faultOnNilArg0:  true,
 		hasSideEffects:  true,
+		unsafePoint:     true,
 		reg: regInfo{
 			inputs: []inputInfo{
 				{1, 805044223},           // R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 R11 R12 R13 R14 R15 R16 R17 R19 R20 R21 R22 R23 R24 R25 R26 g R30
@@ -19045,6 +19049,7 @@ var opcodeTable = [...]opInfo{
 		clobberFlags:    true,
 		faultOnNilArg0:  true,
 		hasSideEffects:  true,
+		unsafePoint:     true,
 		reg: regInfo{
 			inputs: []inputInfo{
 				{1, 805044223},           // R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 R11 R12 R13 R14 R15 R16 R17 R19 R20 R21 R22 R23 R24 R25 R26 g R30
@@ -19063,6 +19068,7 @@ var opcodeTable = [...]opInfo{
 		clobberFlags:    true,
 		faultOnNilArg0:  true,
 		hasSideEffects:  true,
+		unsafePoint:     true,
 		reg: regInfo{
 			inputs: []inputInfo{
 				{1, 805044223},           // R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 R11 R12 R13 R14 R15 R16 R17 R19 R20 R21 R22 R23 R24 R25 R26 g R30
@@ -19080,6 +19086,7 @@ var opcodeTable = [...]opInfo{
 		resultNotInArgs: true,
 		faultOnNilArg0:  true,
 		hasSideEffects:  true,
+		unsafePoint:     true,
 		asm:             arm64.AAND,
 		reg: regInfo{
 			inputs: []inputInfo{
@@ -19097,6 +19104,7 @@ var opcodeTable = [...]opInfo{
 		resultNotInArgs: true,
 		faultOnNilArg0:  true,
 		hasSideEffects:  true,
+		unsafePoint:     true,
 		asm:             arm64.AORR,
 		reg: regInfo{
 			inputs: []inputInfo{
@@ -31564,6 +31572,7 @@ func (o Op) String() string       { return opcodeTable[o].name }
 func (o Op) UsesScratch() bool    { return opcodeTable[o].usesScratch }
 func (o Op) SymEffect() SymEffect { return opcodeTable[o].symEffect }
 func (o Op) IsCall() bool         { return opcodeTable[o].call }
+func (o Op) UnsafePoint() bool    { return opcodeTable[o].unsafePoint }
 
 var registers386 = [...]Register{
 	{0, x86.REG_AX, 0, "AX"},