[release-branch.go1.18] cmd/compile: fix boolean comparison on RISCV64

Following CL 421457, for RISCV64.

May fix RISCV64 builds.

Updates #52788.
Updates #53397.

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>
Reviewed-on: https://go-review.googlesource.com/c/go/+/421460
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>

Author: cherrymui

Diff for: 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))])