From c584f42dcf43351e4cd1e5df22a063f020c00777 Mon Sep 17 00:00:00 2001 From: Joel Sing Date: Mon, 30 Nov 2020 23:47:27 +1100 Subject: [PATCH] cmd/compile: change riscv64 Eq32/Neq32 to zero extend before subtraction As done with other equality tests, zero extend before subtraction rather than after (or in this case, at the same time). While at face value this appears to require more instructions, in reality it allows for most sign extensions to be completely eliminated due to correctly typed loads. Existing optimisations (such as subtraction of zero) then become more effective. This removes more than 10,000 instructions from the Go binary and in particular, a writeBarrier check only requires three instructions (AUIPC, LWU, BNEZ) instead of the current four (AUIPC, LWU, NEGW, BNEZ). Change-Id: I7afdc1921c4916ddbd414c3b3f5c2089107ec016 Reviewed-on: https://go-review.googlesource.com/c/go/+/274066 Trust: Joel Sing Reviewed-by: Cherry Zhang Run-TryBot: Cherry Zhang --- .../compile/internal/ssa/gen/RISCV64.rules | 4 ++-- .../compile/internal/ssa/rewriteRISCV64.go | 22 ++++++++++++++----- 2 files changed, 18 insertions(+), 8 deletions(-) diff --git a/src/cmd/compile/internal/ssa/gen/RISCV64.rules b/src/cmd/compile/internal/ssa/gen/RISCV64.rules index 4380a5efef7..15361fd37a9 100644 --- a/src/cmd/compile/internal/ssa/gen/RISCV64.rules +++ b/src/cmd/compile/internal/ssa/gen/RISCV64.rules @@ -251,7 +251,7 @@ (EqPtr x y) => (SEQZ (SUB x y)) (Eq64 x y) => (SEQZ (SUB x y)) -(Eq32 x y) => (SEQZ (SUBW x y)) +(Eq32 x y) => (SEQZ (SUB (ZeroExt32to64 x) (ZeroExt32to64 y))) (Eq16 x y) => (SEQZ (SUB (ZeroExt16to64 x) (ZeroExt16to64 y))) (Eq8 x y) => (SEQZ (SUB (ZeroExt8to64 x) (ZeroExt8to64 y))) (Eq64F ...) => (FEQD ...) @@ -259,7 +259,7 @@ (NeqPtr x y) => (SNEZ (SUB x y)) (Neq64 x y) => (SNEZ (SUB x y)) -(Neq32 x y) => (SNEZ (SUBW x y)) +(Neq32 x y) => (SNEZ (SUB (ZeroExt32to64 x) (ZeroExt32to64 y))) (Neq16 x y) => (SNEZ (SUB (ZeroExt16to64 x) (ZeroExt16to64 y))) (Neq8 x y) => (SNEZ (SUB (ZeroExt8to64 x) (ZeroExt8to64 y))) (Neq64F ...) => (FNED ...) diff --git a/src/cmd/compile/internal/ssa/rewriteRISCV64.go b/src/cmd/compile/internal/ssa/rewriteRISCV64.go index fb507b65c4c..1abdf1aa063 100644 --- a/src/cmd/compile/internal/ssa/rewriteRISCV64.go +++ b/src/cmd/compile/internal/ssa/rewriteRISCV64.go @@ -890,14 +890,19 @@ func rewriteValueRISCV64_OpEq32(v *Value) bool { v_1 := v.Args[1] v_0 := v.Args[0] b := v.Block + typ := &b.Func.Config.Types // match: (Eq32 x y) - // result: (SEQZ (SUBW x y)) + // result: (SEQZ (SUB (ZeroExt32to64 x) (ZeroExt32to64 y))) for { x := v_0 y := v_1 v.reset(OpRISCV64SEQZ) - v0 := b.NewValue0(v.Pos, OpRISCV64SUBW, x.Type) - v0.AddArg2(x, y) + v0 := b.NewValue0(v.Pos, OpRISCV64SUB, x.Type) + v1 := b.NewValue0(v.Pos, OpZeroExt32to64, typ.UInt64) + v1.AddArg(x) + v2 := b.NewValue0(v.Pos, OpZeroExt32to64, typ.UInt64) + v2.AddArg(y) + v0.AddArg2(v1, v2) v.AddArg(v0) return true } @@ -2466,14 +2471,19 @@ func rewriteValueRISCV64_OpNeq32(v *Value) bool { v_1 := v.Args[1] v_0 := v.Args[0] b := v.Block + typ := &b.Func.Config.Types // match: (Neq32 x y) - // result: (SNEZ (SUBW x y)) + // result: (SNEZ (SUB (ZeroExt32to64 x) (ZeroExt32to64 y))) for { x := v_0 y := v_1 v.reset(OpRISCV64SNEZ) - v0 := b.NewValue0(v.Pos, OpRISCV64SUBW, x.Type) - v0.AddArg2(x, y) + v0 := b.NewValue0(v.Pos, OpRISCV64SUB, x.Type) + v1 := b.NewValue0(v.Pos, OpZeroExt32to64, typ.UInt64) + v1.AddArg(x) + v2 := b.NewValue0(v.Pos, OpZeroExt32to64, typ.UInt64) + v2.AddArg(y) + v0.AddArg2(v1, v2) v.AddArg(v0) return true }