[RISCV] Add hasREV8Like helper to RISCVSubtarget. NFC (#158775)

Author: topperc

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

@@ -378,13 +378,8 @@ RISCVTargetLowering::RISCVTargetLowering(const TargetMachine &TM,
     setOperationAction({ISD::ROTL, ISD::ROTR}, XLenVT, Expand);
   }
 
-  // With Zbb we have an XLen rev8 instruction, but not GREVI. So we'll
-  // pattern match it directly in isel.
   setOperationAction(ISD::BSWAP, XLenVT,
-                     (Subtarget.hasStdExtZbb() || Subtarget.hasStdExtZbkb() ||
-                      Subtarget.hasVendorXTHeadBb())
-                         ? Legal
-                         : Expand);
+                     Subtarget.hasREV8Like() ? Legal : Expand);
 
   if ((Subtarget.hasVendorXCVbitmanip() || Subtarget.hasVendorXqcibm()) &&
       !Subtarget.is64Bit()) {

llvm/lib/Target/RISCV/RISCVSubtarget.h

@@ -196,6 +196,9 @@ class RISCVSubtarget : public RISCVGenSubtargetInfo {
   bool hasCPOPLike() const {
     return HasStdExtZbb || (HasVendorXCVbitmanip && !IsRV64);
   }
+  bool hasREV8Like() const {
+    return HasStdExtZbb || HasStdExtZbkb || HasVendorXTHeadBb;
+  }
 
   bool hasBEXTILike() const { return HasStdExtZbs || HasVendorXTHeadBs; }