[AMDGPUPromoteAlloca][NFC] Avoid unnecessary APInt/int64_t conversions (#157864)

Follow-up to #157682

Author: ritter-x2a

llvm/lib/Target/AMDGPU/AMDGPUPromoteAlloca.cpp

@@ -406,6 +406,7 @@ static Value *GEPToVectorIndex(GetElementPtrInst *GEP, AllocaInst *Alloca,
                                SmallVector<Instruction *> &NewInsts) {
   // TODO: Extracting a "multiple of X" from a GEP might be a useful generic
   // helper.
+  LLVMContext &Ctx = GEP->getContext();
   unsigned BW = DL.getIndexTypeSizeInBits(GEP->getType());
   SmallMapVector<Value *, APInt, 4> VarOffsets;
   APInt ConstOffset(BW, 0);
@@ -438,27 +439,24 @@ static Value *GEPToVectorIndex(GetElementPtrInst *GEP, AllocaInst *Alloca,
 
   assert(CurPtr == Alloca && "GEP not based on alloca");
 
-  unsigned VecElemSize = DL.getTypeAllocSize(VecElemTy);
+  int64_t VecElemSize = DL.getTypeAllocSize(VecElemTy);
   if (VarOffsets.size() > 1)
     return nullptr;
 
   APInt IndexQuot;
-  APInt Rem;
-  APInt::sdivrem(ConstOffset, APInt(ConstOffset.getBitWidth(), VecElemSize),
-                 IndexQuot, Rem);
-  if (!Rem.isZero())
+  int64_t Rem;
+  APInt::sdivrem(ConstOffset, VecElemSize, IndexQuot, Rem);
+  if (Rem != 0)
     return nullptr;
   if (VarOffsets.size() == 0)
-    return ConstantInt::get(GEP->getContext(), IndexQuot);
+    return ConstantInt::get(Ctx, IndexQuot);
 
   IRBuilder<> Builder(GEP);
 
   const auto &VarOffset = VarOffsets.front();
   APInt OffsetQuot;
-  APInt::sdivrem(VarOffset.second,
-                 APInt(VarOffset.second.getBitWidth(), VecElemSize), OffsetQuot,
-                 Rem);
-  if (!Rem.isZero() || OffsetQuot.isZero())
+  APInt::sdivrem(VarOffset.second, VecElemSize, OffsetQuot, Rem);
+  if (Rem != 0 || OffsetQuot.isZero())
     return nullptr;
 
   Value *Offset = VarOffset.first;
@@ -468,7 +466,7 @@ static Value *GEPToVectorIndex(GetElementPtrInst *GEP, AllocaInst *Alloca,
 
   if (!OffsetQuot.isOne()) {
     ConstantInt *ConstMul =
-        ConstantInt::get(OffsetType, OffsetQuot.getSExtValue());
+        ConstantInt::get(Ctx, OffsetQuot.sext(OffsetType->getBitWidth()));
     Offset = Builder.CreateMul(Offset, ConstMul);
     if (Instruction *NewInst = dyn_cast<Instruction>(Offset))
       NewInsts.push_back(NewInst);
@@ -477,7 +475,7 @@ static Value *GEPToVectorIndex(GetElementPtrInst *GEP, AllocaInst *Alloca,
     return Offset;
 
   ConstantInt *ConstIndex =
-      ConstantInt::get(OffsetType, IndexQuot.getSExtValue());
+      ConstantInt::get(Ctx, IndexQuot.sext(OffsetType->getBitWidth()));
   Value *IndexAdd = Builder.CreateAdd(Offset, ConstIndex);
   if (Instruction *NewInst = dyn_cast<Instruction>(IndexAdd))
     NewInsts.push_back(NewInst);