From 7c84e984e675e44a2abc9aa25dd68cb9c9d08ec5 Mon Sep 17 00:00:00 2001 From: David Chase Date: Wed, 20 Aug 2025 12:29:02 -0400 Subject: [PATCH] [dev.simd] cmd/compile: rewrite to elide Slicemask from len==c>0 slicing This might have been something that prove could be educated into figuring out, but this also works, and it also helps prove downstream. Adjusted the prove test, because this change moved a message. Change-Id: I5eabe639eff5db9cd9766a6a8666fdb4973829cb Reviewed-on: https://go-review.googlesource.com/c/go/+/697715 Commit-Queue: David Chase Reviewed-by: Cherry Mui TryBot-Bypass: David Chase --- .../compile/internal/ssa/_gen/generic.rules | 4 + .../compile/internal/ssa/rewritegeneric.go | 87 +++++++++++++++++++ test/prove.go | 4 +- 3 files changed, 93 insertions(+), 2 deletions(-) diff --git a/src/cmd/compile/internal/ssa/_gen/generic.rules b/src/cmd/compile/internal/ssa/_gen/generic.rules index 00e8fcbe32..8583cfae40 100644 --- a/src/cmd/compile/internal/ssa/_gen/generic.rules +++ b/src/cmd/compile/internal/ssa/_gen/generic.rules @@ -989,6 +989,10 @@ (Const64 [0]) (Const64 [0])) +// Special rule to help constant slicing; len > 0 implies cap > 0 implies Slicemask is all 1 +(SliceMake (AddPtr x (And64 y (Slicemask _))) w:(Const64 [c]) z) && c > 0 => (SliceMake (AddPtr x y) w z) +(SliceMake (AddPtr x (And32 y (Slicemask _))) w:(Const32 [c]) z) && c > 0 => (SliceMake (AddPtr x y) w z) + // interface ops (ConstInterface) => (IMake diff --git a/src/cmd/compile/internal/ssa/rewritegeneric.go b/src/cmd/compile/internal/ssa/rewritegeneric.go index fe61ceaff2..c9cff8651b 100644 --- a/src/cmd/compile/internal/ssa/rewritegeneric.go +++ b/src/cmd/compile/internal/ssa/rewritegeneric.go @@ -422,6 +422,8 @@ func rewriteValuegeneric(v *Value) bool { return rewriteValuegeneric_OpSliceCap(v) case OpSliceLen: return rewriteValuegeneric_OpSliceLen(v) + case OpSliceMake: + return rewriteValuegeneric_OpSliceMake(v) case OpSlicePtr: return rewriteValuegeneric_OpSlicePtr(v) case OpSlicemask: @@ -30645,6 +30647,91 @@ func rewriteValuegeneric_OpSliceLen(v *Value) bool { } return false } +func rewriteValuegeneric_OpSliceMake(v *Value) bool { + v_2 := v.Args[2] + v_1 := v.Args[1] + v_0 := v.Args[0] + b := v.Block + // match: (SliceMake (AddPtr x (And64 y (Slicemask _))) w:(Const64 [c]) z) + // cond: c > 0 + // result: (SliceMake (AddPtr x y) w z) + for { + if v_0.Op != OpAddPtr { + break + } + t := v_0.Type + _ = v_0.Args[1] + x := v_0.Args[0] + v_0_1 := v_0.Args[1] + if v_0_1.Op != OpAnd64 { + break + } + _ = v_0_1.Args[1] + v_0_1_0 := v_0_1.Args[0] + v_0_1_1 := v_0_1.Args[1] + for _i0 := 0; _i0 <= 1; _i0, v_0_1_0, v_0_1_1 = _i0+1, v_0_1_1, v_0_1_0 { + y := v_0_1_0 + if v_0_1_1.Op != OpSlicemask { + continue + } + w := v_1 + if w.Op != OpConst64 { + continue + } + c := auxIntToInt64(w.AuxInt) + z := v_2 + if !(c > 0) { + continue + } + v.reset(OpSliceMake) + v0 := b.NewValue0(v.Pos, OpAddPtr, t) + v0.AddArg2(x, y) + v.AddArg3(v0, w, z) + return true + } + break + } + // match: (SliceMake (AddPtr x (And32 y (Slicemask _))) w:(Const32 [c]) z) + // cond: c > 0 + // result: (SliceMake (AddPtr x y) w z) + for { + if v_0.Op != OpAddPtr { + break + } + t := v_0.Type + _ = v_0.Args[1] + x := v_0.Args[0] + v_0_1 := v_0.Args[1] + if v_0_1.Op != OpAnd32 { + break + } + _ = v_0_1.Args[1] + v_0_1_0 := v_0_1.Args[0] + v_0_1_1 := v_0_1.Args[1] + for _i0 := 0; _i0 <= 1; _i0, v_0_1_0, v_0_1_1 = _i0+1, v_0_1_1, v_0_1_0 { + y := v_0_1_0 + if v_0_1_1.Op != OpSlicemask { + continue + } + w := v_1 + if w.Op != OpConst32 { + continue + } + c := auxIntToInt32(w.AuxInt) + z := v_2 + if !(c > 0) { + continue + } + v.reset(OpSliceMake) + v0 := b.NewValue0(v.Pos, OpAddPtr, t) + v0.AddArg2(x, y) + v.AddArg3(v0, w, z) + return true + } + break + } + return false +} func rewriteValuegeneric_OpSlicePtr(v *Value) bool { v_0 := v.Args[0] // match: (SlicePtr (SliceMake (SlicePtr x) _ _)) diff --git a/test/prove.go b/test/prove.go index 70a27865cf..6d2bb0962b 100644 --- a/test/prove.go +++ b/test/prove.go @@ -511,10 +511,10 @@ func f19() (e int64, err error) { func sm1(b []int, x int) { // Test constant argument to slicemask. - useSlice(b[2:8]) // ERROR "Proved slicemask not needed$" + useSlice(b[2:8]) // optimized away earlier by rewrite // Test non-constant argument with known limits. if cap(b) > 10 { - useSlice(b[2:]) + useSlice(b[2:]) // ERROR "Proved slicemask not needed$" } } -- 2.52.0