cmd/compile: fix boolean comparison on RISCV64

Following CL 405114, for RISCV64.

May fix RISCV64 builds.

Updates #52788.

Change-Id: Ifc34658703d1e8b97665e7b862060152e3005d71
Reviewed-on: https://go-review.googlesource.com/c/go/+/405553
Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>

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

@@ -583,7 +583,7 @@
 (AtomicOr32  ...) => (LoweredAtomicOr32  ...)
 
 // Conditional branches
-(If cond yes no) => (BNEZ cond yes no)
+(If cond yes no) => (BNEZ (MOVBUreg <typ.UInt64> cond) yes no)
 
 // Optimizations
 
@@ -621,6 +621,10 @@
 (MOVWstore [off] {sym} ptr (MOVDconst [0]) mem) => (MOVWstorezero [off] {sym} ptr mem)
 (MOVDstore [off] {sym} ptr (MOVDconst [0]) mem) => (MOVDstorezero [off] {sym} ptr mem)
 
+// Boolean ops are already extended.
+(MOVBUreg x:((SEQZ|SNEZ) _)) => x
+(MOVBUreg x:((SLT|SLTU) _ _)) => x
+
 // Avoid sign/zero extension for consts.
 (MOVBreg  (MOVDconst [c])) => (MOVDconst [int64(int8(c))])
 (MOVHreg  (MOVDconst [c])) => (MOVDconst [int64(int16(c))])

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

@@ -3152,6 +3152,46 @@ func rewriteValueRISCV64_OpRISCV64MOVBUload(v *Value) bool {
 func rewriteValueRISCV64_OpRISCV64MOVBUreg(v *Value) bool {
 	v_0 := v.Args[0]
 	b := v.Block
+	// match: (MOVBUreg x:(SEQZ _))
+	// result: x
+	for {
+		x := v_0
+		if x.Op != OpRISCV64SEQZ {
+			break
+		}
+		v.copyOf(x)
+		return true
+	}
+	// match: (MOVBUreg x:(SNEZ _))
+	// result: x
+	for {
+		x := v_0
+		if x.Op != OpRISCV64SNEZ {
+			break
+		}
+		v.copyOf(x)
+		return true
+	}
+	// match: (MOVBUreg x:(SLT _ _))
+	// result: x
+	for {
+		x := v_0
+		if x.Op != OpRISCV64SLT {
+			break
+		}
+		v.copyOf(x)
+		return true
+	}
+	// match: (MOVBUreg x:(SLTU _ _))
+	// result: x
+	for {
+		x := v_0
+		if x.Op != OpRISCV64SLTU {
+			break
+		}
+		v.copyOf(x)
+		return true
+	}
 	// match: (MOVBUreg (MOVDconst [c]))
 	// result: (MOVDconst [int64(uint8(c))])
 	for {
@@ -6483,6 +6523,7 @@ func rewriteValueRISCV64_OpZero(v *Value) bool {
 	}
 }
 func rewriteBlockRISCV64(b *Block) bool {
+	typ := &b.Func.Config.Types
 	switch b.Kind {
 	case BlockRISCV64BEQ:
 		// match: (BEQ (MOVDconst [0]) cond yes no)
@@ -6690,10 +6731,12 @@ func rewriteBlockRISCV64(b *Block) bool {
 		}
 	case BlockIf:
 		// match: (If cond yes no)
-		// result: (BNEZ cond yes no)
+		// result: (BNEZ (MOVBUreg <typ.UInt64> cond) yes no)
 		for {
 			cond := b.Controls[0]
-			b.resetWithControl(BlockRISCV64BNEZ, cond)
+			v0 := b.NewValue0(cond.Pos, OpRISCV64MOVBUreg, typ.UInt64)
+			v0.AddArg(cond)
+			b.resetWithControl(BlockRISCV64BNEZ, v0)
 			return true
 		}
 	}