Fix incorrect GEP bitwidth in areNonOverlapSameBaseLoadAndStore()

[arichardson]

Summary

When using a datalayout that has pointer index width != pointer size this
code triggers an assertion in Value::stripAndAccumulateConstantOffsets().
I encountered this this while compiling FreeBSD for CHERI-RISC-V.
Also update LoadsTest.cpp to use a DataLayout with index width != pointer
width to ensure this case is tested.

[nikic]

LGTM

llvm/lib/Analysis/Loads.cpp

 
 // Check if the load and the store have the same base, constant offsets and
 // non-overlapping access ranges.
 static bool areNonOverlapSameBaseLoadAndStore(const Value *LoadPtr,
                                               Type *LoadTy,
                                               const Value *StorePtr,
                                               Type *StoreTy,
                                               const DataLayout &DL) {
-  APInt LoadOffset(DL.getTypeSizeInBits(LoadPtr->getType()), 0);
-  APInt StoreOffset(DL.getTypeSizeInBits(StorePtr->getType()), 0);
+  APInt LoadOffset(DL.getIndexTypeSizeInBits(LoadPtr->getType()), 0);
+  APInt StoreOffset(DL.getIndexTypeSizeInBits(StorePtr->getType()), 0);
   const Value *LoadBase = LoadPtr->stripAndAccumulateConstantOffsets(
       DL, LoadOffset, /* AllowNonInbounds */ false);
   const Value *StoreBase = StorePtr->stripAndAccumulateConstantOffsets(
       DL, StoreOffset, /* AllowNonInbounds */ false);
   if (LoadBase != StoreBase)
     return false;
   auto LoadAccessSize = LocationSize::precise(DL.getTypeStoreSize(LoadTy));
   auto StoreAccessSize = LocationSize::precise(DL.getTypeStoreSize(StoreTy));

llvm/unittests/Analysis/LoadsTest.cpp

if (!Mod)
     Err.print("AnalysisTests", errs());
   return Mod;
 }
 
 TEST(LoadsTest, FindAvailableLoadedValueSameBasePtrConstantOffsetsNullAA) {
   LLVMContext C;
   std::unique_ptr<Module> M = parseIR(C,
                                       R"IR(
+target datalayout = "p:64:64:64:32"
 %class = type <{ i32, i32 }>
 
 define i32 @f() {
 entry:
   %o = alloca %class
   %f1 = getelementptr inbounds %class, %class* %o, i32 0, i32 0
   store i32 42, i32* %f1
   %f2 = getelementptr inbounds %class, %class* %o, i32 0, i32 1