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cmd/compile: sign-extend the 2nd argument of the LoweredAtomicCas32 on loong64,mips64x,riscv64

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The function LoweredAtomicCas32 is implemented using the LL-SC instruction pair
on loong64, mips64x, riscv64. However,the LL instruction on loong64, mips64x,
riscv64 is sign-extended, so it is necessary to sign-extend the 2nd parameter
"old" of the LoweredAtomicCas32, so that the instruction BNE after LL can get
the desired result.

The function prototype of LoweredAtomicCas32 in golang:
    func Cas32(ptr *uint32, old, new uint32) bool

When using an intrinsify implementation:
    case 1: (*ptr) <= 0x80000000 && old < 0x80000000
        E.g: (*ptr) = 0x7FFFFFFF, old = Rarg1= 0x7FFFFFFF

        After run the instruction "LL (Rarg0), Rtmp": Rtmp = 0x7FFFFFFF
        Rtmp ! = Rarg1(old) is false, the result we expect

    case 2: (*ptr) >= 0x80000000 && old >= 0x80000000
        E.g: (*ptr) = 0x80000000, old = Rarg1= 0x80000000

        After run the instruction "LL (Rarg0), Rtmp": Rtmp = 0xFFFFFFFF_80000000
        Rtmp ! = Rarg1(old) is true, which we do not expect

When using an non-intrinsify implementation:
    Because Rarg1 is loaded from the stack using sign-extended instructions
    ld.w, the situation described in Case 2 above does not occur

Benchmarks on linux/loong64:
name     old time/op  new time/op  delta
Cas      50.0ns ± 0%  50.1ns ± 0%   ~     (p=1.000 n=1+1)
Cas64    50.0ns ± 0%  50.1ns ± 0%   ~     (p=1.000 n=1+1)
Cas-4    56.0ns ± 0%  56.0ns ± 0%   ~     (p=1.000 n=1+1)
Cas64-4  56.0ns ± 0%  56.0ns ± 0%   ~     (p=1.000 n=1+1)

Benchmarks on Loongson 3A4000 (GOARCH=mips64le, 1.8GHz)
name     old time/op  new time/op  delta
Cas      70.4ns ± 0%  70.3ns ± 0%   ~     (p=1.000 n=1+1)
Cas64    70.7ns ± 0%  70.6ns ± 0%   ~     (p=1.000 n=1+1)
Cas-4    81.1ns ± 0%  80.8ns ± 0%   ~     (p=1.000 n=1+1)
Cas64-4  80.9ns ± 0%  80.9ns ± 0%   ~     (p=1.000 n=1+1)

Fixes #57282

Change-Id: I190a7fc648023b15fa392f7fdda5ac18c1561bac
Reviewed-on: https://go-review.googlesource.com/c/go/+/457135
Run-TryBot: Than McIntosh <thanm@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Wayne Zuo <wdvxdr@golangcn.org>
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: David Chase <drchase@google.com>
This commit is contained in:
Guoqi Chen 2022-12-19 05:04:48 +08:00 • committed by David Chase
parent 8bcc490667
commit 0b2ad1d815
7 changed files with 101 additions and 9 deletions
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24
src/cmd/compile/internal/ssa/rewriteRISCV64.go
View file

@ -61,8 +61,7 @@ func rewriteValueRISCV64(v *Value) bool {
case OpAtomicAnd8:
return rewriteValueRISCV64_OpAtomicAnd8(v)
case OpAtomicCompareAndSwap32:
v.Op = OpRISCV64LoweredAtomicCas32
return true
return rewriteValueRISCV64_OpAtomicCompareAndSwap32(v)
case OpAtomicCompareAndSwap64:
v.Op = OpRISCV64LoweredAtomicCas64
return true
@ -776,6 +775,27 @@ func rewriteValueRISCV64_OpAtomicAnd8(v *Value) bool {
return true
}
}
func rewriteValueRISCV64_OpAtomicCompareAndSwap32(v *Value) bool {
v_3 := v.Args[3]
v_2 := v.Args[2]
v_1 := v.Args[1]
v_0 := v.Args[0]
b := v.Block
typ := &b.Func.Config.Types
// match: (AtomicCompareAndSwap32 ptr old new mem)
// result: (LoweredAtomicCas32 ptr (SignExt32to64 old) new mem)
for {
ptr := v_0
old := v_1
new := v_2
mem := v_3
v.reset(OpRISCV64LoweredAtomicCas32)
v0 := b.NewValue0(v.Pos, OpSignExt32to64, typ.Int64)
v0.AddArg(old)
v.AddArg4(ptr, v0, new, mem)
return true
}
}
func rewriteValueRISCV64_OpAtomicOr8(v *Value) bool {
v_2 := v.Args[2]
v_1 := v.Args[1]