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Commit 4a7ed1f

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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>
1 parent 0f992b9 commit 4a7ed1f

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5 files changed

+32
-8
lines changed

5 files changed

+32
-8
lines changed

‎src/cmd/compile/internal/gc/plive.go

Lines changed: 9 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -639,6 +639,15 @@ func (lv *Liveness) markUnsafePoints() {
639639

640640
lv.unsafePoints = bvalloc(int32(lv.f.NumValues()))
641641

642+
// Mark architecture-specific unsafe pointes.
643+
for _, b := range lv.f.Blocks {
644+
for _, v := range b.Values {
645+
if v.Op.UnsafePoint() {
646+
lv.unsafePoints.Set(int32(v.ID))
647+
}
648+
}
649+
}
650+
642651
// Mark write barrier unsafe points.
643652
for _, wbBlock := range lv.f.WBLoads {
644653
if wbBlock.Kind == ssa.BlockPlain && len(wbBlock.Values) == 0 {

‎src/cmd/compile/internal/ssa/gen/ARM64Ops.go

Lines changed: 8 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -620,17 +620,17 @@ func init() {
620620
// LDAXR (Rarg0), Rout
621621
// STLXR Rarg1, (Rarg0), Rtmp
622622
// CBNZ Rtmp, -2(PC)
623-
{name: "LoweredAtomicExchange64", argLength: 3, reg: gpxchg, resultNotInArgs: true, faultOnNilArg0: true, hasSideEffects: true},
624-
{name: "LoweredAtomicExchange32", argLength: 3, reg: gpxchg, resultNotInArgs: true, faultOnNilArg0: true, hasSideEffects: true},
623+
{name: "LoweredAtomicExchange64", argLength: 3, reg: gpxchg, resultNotInArgs: true, faultOnNilArg0: true, hasSideEffects: true, unsafePoint: true},
624+
{name: "LoweredAtomicExchange32", argLength: 3, reg: gpxchg, resultNotInArgs: true, faultOnNilArg0: true, hasSideEffects: true, unsafePoint: true},
625625

626626
// atomic add.
627627
// *arg0 += arg1. arg2=mem. returns <new content of *arg0, memory>. auxint must be zero.
628628
// LDAXR (Rarg0), Rout
629629
// ADD Rarg1, Rout
630630
// STLXR Rout, (Rarg0), Rtmp
631631
// CBNZ Rtmp, -3(PC)
632-
{name: "LoweredAtomicAdd64", argLength: 3, reg: gpxchg, resultNotInArgs: true, faultOnNilArg0: true, hasSideEffects: true},
633-
{name: "LoweredAtomicAdd32", argLength: 3, reg: gpxchg, resultNotInArgs: true, faultOnNilArg0: true, hasSideEffects: true},
632+
{name: "LoweredAtomicAdd64", argLength: 3, reg: gpxchg, resultNotInArgs: true, faultOnNilArg0: true, hasSideEffects: true, unsafePoint: true},
633+
{name: "LoweredAtomicAdd32", argLength: 3, reg: gpxchg, resultNotInArgs: true, faultOnNilArg0: true, hasSideEffects: true, unsafePoint: true},
634634

635635
// atomic add variant.
636636
// *arg0 += arg1. arg2=mem. returns <new content of *arg0, memory>. auxint must be zero.
@@ -653,17 +653,17 @@ func init() {
653653
// STLXR Rarg2, (Rarg0), Rtmp
654654
// CBNZ Rtmp, -4(PC)
655655
// CSET EQ, Rout
656-
{name: "LoweredAtomicCas64", argLength: 4, reg: gpcas, resultNotInArgs: true, clobberFlags: true, faultOnNilArg0: true, hasSideEffects: true},
657-
{name: "LoweredAtomicCas32", argLength: 4, reg: gpcas, resultNotInArgs: true, clobberFlags: true, faultOnNilArg0: true, hasSideEffects: true},
656+
{name: "LoweredAtomicCas64", argLength: 4, reg: gpcas, resultNotInArgs: true, clobberFlags: true, faultOnNilArg0: true, hasSideEffects: true, unsafePoint: true},
657+
{name: "LoweredAtomicCas32", argLength: 4, reg: gpcas, resultNotInArgs: true, clobberFlags: true, faultOnNilArg0: true, hasSideEffects: true, unsafePoint: true},
658658

659659
// atomic and/or.
660660
// *arg0 &= (|=) arg1. arg2=mem. returns <new content of *arg0, memory>. auxint must be zero.
661661
// LDAXRB (Rarg0), Rout
662662
// AND/OR Rarg1, Rout
663663
// STLXRB Rout, (Rarg0), Rtmp
664664
// CBNZ Rtmp, -3(PC)
665-
{name: "LoweredAtomicAnd8", argLength: 3, reg: gpxchg, resultNotInArgs: true, asm: "AND", typ: "(UInt8,Mem)", faultOnNilArg0: true, hasSideEffects: true},
666-
{name: "LoweredAtomicOr8", argLength: 3, reg: gpxchg, resultNotInArgs: true, asm: "ORR", typ: "(UInt8,Mem)", faultOnNilArg0: true, hasSideEffects: true},
665+
{name: "LoweredAtomicAnd8", argLength: 3, reg: gpxchg, resultNotInArgs: true, asm: "AND", typ: "(UInt8,Mem)", faultOnNilArg0: true, hasSideEffects: true, unsafePoint: true},
666+
{name: "LoweredAtomicOr8", argLength: 3, reg: gpxchg, resultNotInArgs: true, asm: "ORR", typ: "(UInt8,Mem)", faultOnNilArg0: true, hasSideEffects: true, unsafePoint: true},
667667

668668
// LoweredWB invokes runtime.gcWriteBarrier. arg0=destptr, arg1=srcptr, arg2=mem, aux=runtime.gcWriteBarrier
669669
// It saves all GP registers if necessary,

‎src/cmd/compile/internal/ssa/gen/main.go

Lines changed: 5 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -63,6 +63,7 @@ type opData struct {
6363
usesScratch bool // this op requires scratch memory space
6464
hasSideEffects bool // for "reasons", not to be eliminated. E.g., atomic store, #19182.
6565
zeroWidth bool // op never translates into any machine code. example: copy, which may sometimes translate to machine code, is not zero-width.
66+
unsafePoint bool // this op is an unsafe point, i.e. not safe for async preemption
6667
symEffect string // effect this op has on symbol in aux
6768
scale uint8 // amd64/386 indexed load scale
6869
}
@@ -325,6 +326,9 @@ func genOp() {
325326
if v.zeroWidth {
326327
fmt.Fprintln(w, "zeroWidth: true,")
327328
}
329+
if v.unsafePoint {
330+
fmt.Fprintln(w, "unsafePoint: true,")
331+
}
328332
needEffect := strings.HasPrefix(v.aux, "Sym")
329333
if v.symEffect != "" {
330334
if !needEffect {
@@ -401,6 +405,7 @@ func genOp() {
401405

402406
fmt.Fprintln(w, "func (o Op) SymEffect() SymEffect { return opcodeTable[o].symEffect }")
403407
fmt.Fprintln(w, "func (o Op) IsCall() bool { return opcodeTable[o].call }")
408+
fmt.Fprintln(w, "func (o Op) UnsafePoint() bool { return opcodeTable[o].unsafePoint }")
404409

405410
// generate registers
406411
for _, a := range archs {

‎src/cmd/compile/internal/ssa/op.go

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -36,6 +36,7 @@ type opInfo struct {
3636
usesScratch bool // this op requires scratch memory space
3737
hasSideEffects bool // for "reasons", not to be eliminated. E.g., atomic store, #19182.
3838
zeroWidth bool // op never translates into any machine code. example: copy, which may sometimes translate to machine code, is not zero-width.
39+
unsafePoint bool // this op is an unsafe point, i.e. not safe for async preemption
3940
symEffect SymEffect // effect this op has on symbol in aux
4041
scale uint8 // amd64/386 indexed load scale
4142
}

‎src/cmd/compile/internal/ssa/opGen.go

Lines changed: 9 additions & 0 deletions
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