cmd/compile: remove NEG when used with SEQZ/SNEZ on riscv64

The negation does not change the comparison to zero.

Also remove unnecessary x.Uses == 1 condition from equivalent BEQZ/BNEZ rules.

Change-Id: I62dd8e383e42bfe5c46d11bbf78d8e5ff862a1d5
Reviewed-on: https://go-review.googlesource.com/c/go/+/426262
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: Heschi Kreinick <heschi@google.com>

src/cmd/compile/internal/ssa/gen/RISCV64.rules

@@ -601,9 +601,9 @@
 (BNEZ (SEQZ x) yes no) => (BEQZ x yes no)
 (BNEZ (SNEZ x) yes no) => (BNEZ x yes no)
 
-// Absorb NEG into branch when possible.
+// Absorb NEG into branch.
-(BEQZ x:(NEG y) yes no) && x.Uses == 1 => (BEQZ y yes no)
+(BEQZ (NEG x) yes no) => (BEQZ x yes no)
-(BNEZ x:(NEG y) yes no) && x.Uses == 1 => (BNEZ y yes no)
+(BNEZ (NEG x) yes no) => (BNEZ x yes no)
 
 // Convert BEQZ/BNEZ into more optimal branch conditions.
 (BEQZ (SUB x y) yes no) => (BEQ x y yes no)
@@ -623,6 +623,10 @@
 (BGE (MOVDconst [0]) cond yes no) => (BLEZ cond yes no)
 (BGE cond (MOVDconst [0]) yes no) => (BGEZ cond yes no)
 
+// Remove NEG when used with SEQZ/SNEZ.
+(SEQZ (NEG x)) => (SEQZ x)
+(SNEZ (NEG x)) => (SNEZ x)
+
 // Store zero
 (MOVBstore [off] {sym} ptr (MOVDconst [0]) mem) => (MOVBstorezero [off] {sym} ptr mem)
 (MOVHstore [off] {sym} ptr (MOVDconst [0]) mem) => (MOVHstorezero [off] {sym} ptr mem)

src/cmd/compile/internal/ssa/rewriteRISCV64.go

@@ -505,6 +505,8 @@ func rewriteValueRISCV64(v *Value) bool {
 		return rewriteValueRISCV64_OpRISCV64OR(v)
 	case OpRISCV64ORI:
 		return rewriteValueRISCV64_OpRISCV64ORI(v)
+	case OpRISCV64SEQZ:
+		return rewriteValueRISCV64_OpRISCV64SEQZ(v)
 	case OpRISCV64SLL:
 		return rewriteValueRISCV64_OpRISCV64SLL(v)
 	case OpRISCV64SLLI:
@@ -517,6 +519,8 @@ func rewriteValueRISCV64(v *Value) bool {
 		return rewriteValueRISCV64_OpRISCV64SLTIU(v)
 	case OpRISCV64SLTU:
 		return rewriteValueRISCV64_OpRISCV64SLTU(v)
+	case OpRISCV64SNEZ:
+		return rewriteValueRISCV64_OpRISCV64SNEZ(v)
 	case OpRISCV64SRA:
 		return rewriteValueRISCV64_OpRISCV64SRA(v)
 	case OpRISCV64SRAI:
@@ -5000,6 +5004,21 @@ func rewriteValueRISCV64_OpRISCV64ORI(v *Value) bool {
 	}
 	return false
 }
+func rewriteValueRISCV64_OpRISCV64SEQZ(v *Value) bool {
+	v_0 := v.Args[0]
+	// match: (SEQZ (NEG x))
+	// result: (SEQZ x)
+	for {
+		if v_0.Op != OpRISCV64NEG {
+			break
+		}
+		x := v_0.Args[0]
+		v.reset(OpRISCV64SEQZ)
+		v.AddArg(x)
+		return true
+	}
+	return false
+}
 func rewriteValueRISCV64_OpRISCV64SLL(v *Value) bool {
 	v_1 := v.Args[1]
 	v_0 := v.Args[0]
@@ -5102,6 +5121,21 @@ func rewriteValueRISCV64_OpRISCV64SLTU(v *Value) bool {
 	}
 	return false
 }
+func rewriteValueRISCV64_OpRISCV64SNEZ(v *Value) bool {
+	v_0 := v.Args[0]
+	// match: (SNEZ (NEG x))
+	// result: (SNEZ x)
+	for {
+		if v_0.Op != OpRISCV64NEG {
+			break
+		}
+		x := v_0.Args[0]
+		v.reset(OpRISCV64SNEZ)
+		v.AddArg(x)
+		return true
+	}
+	return false
+}
 func rewriteValueRISCV64_OpRISCV64SRA(v *Value) bool {
 	v_1 := v.Args[1]
 	v_0 := v.Args[0]
@@ -6893,16 +6927,12 @@ func rewriteBlockRISCV64(b *Block) bool {
 			b.resetWithControl(BlockRISCV64BEQZ, x)
 			return true
 		}
-		// match: (BEQZ x:(NEG y) yes no)
+		// match: (BEQZ (NEG x) yes no)
-		// cond: x.Uses == 1
+		// result: (BEQZ x yes no)
-		// result: (BEQZ y yes no)
 		for b.Controls[0].Op == OpRISCV64NEG {
-			x := b.Controls[0]
+			v_0 := b.Controls[0]
-			y := x.Args[0]
+			x := v_0.Args[0]
-			if !(x.Uses == 1) {
+			b.resetWithControl(BlockRISCV64BEQZ, x)
-				break
-			}
-			b.resetWithControl(BlockRISCV64BEQZ, y)
 			return true
 		}
 		// match: (BEQZ (SUB x y) yes no)
@@ -7018,16 +7048,12 @@ func rewriteBlockRISCV64(b *Block) bool {
 			b.resetWithControl(BlockRISCV64BNEZ, x)
 			return true
 		}
-		// match: (BNEZ x:(NEG y) yes no)
+		// match: (BNEZ (NEG x) yes no)
-		// cond: x.Uses == 1
+		// result: (BNEZ x yes no)
-		// result: (BNEZ y yes no)
 		for b.Controls[0].Op == OpRISCV64NEG {
-			x := b.Controls[0]
+			v_0 := b.Controls[0]
-			y := x.Args[0]
+			x := v_0.Args[0]
-			if !(x.Uses == 1) {
+			b.resetWithControl(BlockRISCV64BNEZ, x)
-				break
-			}
-			b.resetWithControl(BlockRISCV64BNEZ, y)
 			return true
 		}
 		// match: (BNEZ (SUB x y) yes no)