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| author | Mark Ryan <markdryan@rivosinc.com> | 2025-11-13 12:28:29 +0100 |
|---|---|---|
| committer | Gopher Robot <gobot@golang.org> | 2025-11-14 11:01:26 -0800 |
| commit | a0e738c657d33e2a648838546812fb50cf42e41d (patch) | |
| tree | 11e98e584095a39f897723b2386960a4be9a7742 /src/cmd | |
| parent | 2cdcc4150bc577e0b40a9cedaaa7c8301f2860cd (diff) | |
| download | go-a0e738c657d33e2a648838546812fb50cf42e41d.tar.xz | |
cmd/compile/internal: remove incorrect riscv64 SLTI rule
The rule
(SLTI [x] (ORI [y] _)) && y >= 0 && int64(y) >= int64(x) => (MOVDconst [0])
is incorrect as it only generates correct code if the unknown value
being compared is >= 0. If the unknown value is < 0 the rule will
incorrectly produce a constant value of 0, whereas the code optimized
away by the rule would have produced a value of 1.
A new test that causes the faulty rule to generate incorrect code
is also added to ensure that the error does not return.
Change-Id: I69224e0776596f1b9538acf9dacf9009d305f966
Reviewed-on: https://go-review.googlesource.com/c/go/+/720220
Reviewed-by: Meng Zhuo <mengzhuo1203@gmail.com>
Reviewed-by: Junyang Shao <shaojunyang@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Joel Sing <joel@sing.id.au>
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Diffstat (limited to 'src/cmd')
| -rw-r--r-- | src/cmd/compile/internal/ssa/_gen/RISCV64.rules | 1 | ||||
| -rw-r--r-- | src/cmd/compile/internal/ssa/rewriteRISCV64.go | 16 | ||||
| -rw-r--r-- | src/cmd/compile/internal/test/testdata/arith_test.go | 14 |
3 files changed, 14 insertions, 17 deletions
diff --git a/src/cmd/compile/internal/ssa/_gen/RISCV64.rules b/src/cmd/compile/internal/ssa/_gen/RISCV64.rules index 6166bd5584..13a8cab3b5 100644 --- a/src/cmd/compile/internal/ssa/_gen/RISCV64.rules +++ b/src/cmd/compile/internal/ssa/_gen/RISCV64.rules @@ -792,7 +792,6 @@ // SLTI/SLTIU with known outcomes. (SLTI [x] (ANDI [y] _)) && y >= 0 && int64(y) < int64(x) => (MOVDconst [1]) (SLTIU [x] (ANDI [y] _)) && y >= 0 && uint64(y) < uint64(x) => (MOVDconst [1]) -(SLTI [x] (ORI [y] _)) && y >= 0 && int64(y) >= int64(x) => (MOVDconst [0]) (SLTIU [x] (ORI [y] _)) && y >= 0 && uint64(y) >= uint64(x) => (MOVDconst [0]) // SLT/SLTU with known outcomes. diff --git a/src/cmd/compile/internal/ssa/rewriteRISCV64.go b/src/cmd/compile/internal/ssa/rewriteRISCV64.go index 24fef3fe72..284d88967b 100644 --- a/src/cmd/compile/internal/ssa/rewriteRISCV64.go +++ b/src/cmd/compile/internal/ssa/rewriteRISCV64.go @@ -7362,22 +7362,6 @@ func rewriteValueRISCV64_OpRISCV64SLTI(v *Value) bool { v.AuxInt = int64ToAuxInt(1) return true } - // match: (SLTI [x] (ORI [y] _)) - // cond: y >= 0 && int64(y) >= int64(x) - // result: (MOVDconst [0]) - for { - x := auxIntToInt64(v.AuxInt) - if v_0.Op != OpRISCV64ORI { - break - } - y := auxIntToInt64(v_0.AuxInt) - if !(y >= 0 && int64(y) >= int64(x)) { - break - } - v.reset(OpRISCV64MOVDconst) - v.AuxInt = int64ToAuxInt(0) - return true - } return false } func rewriteValueRISCV64_OpRISCV64SLTIU(v *Value) bool { diff --git a/src/cmd/compile/internal/test/testdata/arith_test.go b/src/cmd/compile/internal/test/testdata/arith_test.go index 8984cd3e26..34ac73c068 100644 --- a/src/cmd/compile/internal/test/testdata/arith_test.go +++ b/src/cmd/compile/internal/test/testdata/arith_test.go @@ -445,6 +445,19 @@ func testBitwiseRshU_ssa(a uint32, b, c uint32) uint32 { } //go:noinline +func orLt_ssa(x int) bool { + y := x - x + return (x | 2) < y +} + +// test riscv64 SLTI rules +func testSetIfLessThan(t *testing.T) { + if want, got := true, orLt_ssa(-7); got != want { + t.Errorf("orLt_ssa(-7) = %t want %t", got, want) + } +} + +//go:noinline func testShiftCX_ssa() int { v1 := uint8(3) v4 := (v1 * v1) ^ v1 | v1 - v1 - v1&v1 ^ uint8(3+2) + v1*1>>0 - v1 | 1 | v1<<(2*3|0-0*0^1) @@ -977,6 +990,7 @@ func TestArithmetic(t *testing.T) { testRegallocCVSpill(t) testSubqToNegq(t) testBitwiseLogic(t) + testSetIfLessThan(t) testOcom(t) testLrot(t) testShiftCX(t) |