[RISCV] Use heuristic getPreferredAddressingMode

See https://reviews.llvm.org/D96600 for details

Author: PhilippvK

llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp

@@ -1012,6 +1012,15 @@ bool RISCVTTIImpl::shouldFavorPostInc() const {
   return ST->hasExtXcvmem();
 }
 
+TTI::AddressingModeKind
+RISCVTTIImpl::getPreferredAddressingMode(const Loop *L,
+                                       ScalarEvolution *SE) const {
+  if (ST->hasExtXcvmem())
+    return TTI::AMK_PostIndexed;
+
+  return TTI::AMK_None;
+}
+
 bool RISCVTTIImpl::isHardwareLoopProfitable(Loop *L, ScalarEvolution &SE,
                                             AssumptionCache &AC,
                                             TargetLibraryInfo *LibInfo,

llvm/lib/Target/RISCV/RISCVTargetTransformInfo.h

@@ -308,8 +308,11 @@ class RISCVTTIImpl : public BasicTTIImplBase<RISCVTTIImpl> {
     }
     llvm_unreachable("unknown register class");
   }
-  
+
   bool shouldFavorPostInc() const;
+  TTI::AddressingModeKind
+    getPreferredAddressingMode(const Loop *L, ScalarEvolution *SE) const;
+
   bool isHardwareLoopProfitable(Loop *L, ScalarEvolution &SE,
                                 AssumptionCache &AC,
                                 TargetLibraryInfo *LibInfo,