[RISCV] Use llvm::bit_floor and std::clamp (NFC)

Author: kazutakahirata

llvm/lib/Target/RISCV/RISCVSubtarget.cpp

@@ -157,8 +157,7 @@ unsigned RISCVSubtarget::getMaxLMULForFixedLengthVectors() const {
          "Tried to get vector length without Zve or V extension support!");
   assert(RVVVectorLMULMax <= 8 && isPowerOf2_32(RVVVectorLMULMax) &&
          "V extension requires a LMUL to be at most 8 and a power of 2!");
-  return PowerOf2Floor(
-      std::max<unsigned>(std::min<unsigned>(RVVVectorLMULMax, 8), 1));
+  return llvm::bit_floor(std::clamp<unsigned>(RVVVectorLMULMax, 1, 8));
 }
 
 bool RISCVSubtarget::useRVVForFixedLengthVectors() const {

llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp

@@ -222,8 +222,8 @@ std::optional<unsigned> RISCVTTIImpl::getVScaleForTuning() const {
 
 TypeSize
 RISCVTTIImpl::getRegisterBitWidth(TargetTransformInfo::RegisterKind K) const {
-  unsigned LMUL = PowerOf2Floor(
-      std::max<unsigned>(std::min<unsigned>(RVVRegisterWidthLMUL, 8), 1));
+  unsigned LMUL =
+      llvm::bit_floor(std::clamp<unsigned>(RVVRegisterWidthLMUL, 1, 8));
   switch (K) {
   case TargetTransformInfo::RGK_Scalar:
     return TypeSize::getFixed(ST->getXLen());