cmd/compile/internal/ssagen: set BitLen32 as intrinsic on PPC64

It was noticed through some other investigation that BitLen32
was not generating the best code and found that it wasn't recognized
as an intrinsic. This corrects that and enables the test for PPC64.

Change-Id: Iab496a8830c8552f507b7292649b1b660f3848b5
Reviewed-on: https://go-review.googlesource.com/c/go/+/355872
Run-TryBot: Lynn Boger <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Trust: Lynn Boger <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>

Author: laboger

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

@@ -4421,7 +4421,7 @@ func InitTables() {
 		func(s *state, n *ir.CallExpr, args []*ssa.Value) *ssa.Value {
 			return s.newValue1(ssa.OpBitLen32, types.Types[types.TINT], args[0])
 		},
-		sys.AMD64, sys.ARM64)
+		sys.AMD64, sys.ARM64, sys.PPC64)
 	addF("math/bits", "Len32",
 		func(s *state, n *ir.CallExpr, args []*ssa.Value) *ssa.Value {
 			if s.config.PtrSize == 4 {
@@ -4430,7 +4430,7 @@ func InitTables() {
 			x := s.newValue1(ssa.OpZeroExt32to64, types.Types[types.TUINT64], args[0])
 			return s.newValue1(ssa.OpBitLen64, types.Types[types.TINT], x)
 		},
-		sys.ARM, sys.S390X, sys.MIPS, sys.PPC64, sys.Wasm)
+		sys.ARM, sys.S390X, sys.MIPS, sys.Wasm)
 	addF("math/bits", "Len16",
 		func(s *state, n *ir.CallExpr, args []*ssa.Value) *ssa.Value {
 			if s.config.PtrSize == 4 {

test/codegen/mathbits.go

@@ -93,6 +93,8 @@ func Len32(n uint32) int {
 	// arm:"CLZ" arm64:"CLZ"
 	// mips:"CLZ"
 	// wasm:"I64Clz"
+	// ppc64: "CNTLZW"
+	// ppc64le: "CNTLZW"
 	return bits.Len32(n)
 }