[llvm] [InstCombine] Handle more scalable geps in EmitGEPOffset (PR #71699)

[Nikita Popov via llvm-commits]

================
@@ -36,25 +36,18 @@ Value *llvm::emitGEPOffset(IRBuilderBase *Builder, const DataLayout &DL,
       Result = Offset;
   };
 
-  // Build a mask for high order bits.
-  unsigned IntPtrWidth = IntIdxTy->getScalarType()->getIntegerBitWidth();
-  uint64_t PtrSizeMask =
-      std::numeric_limits<uint64_t>::max() >> (64 - IntPtrWidth);
-
   gep_type_iterator GTI = gep_type_begin(GEP);
   for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end(); i != e;
        ++i, ++GTI) {
     Value *Op = *i;
-    TypeSize TSize = DL.getTypeAllocSize(GTI.getIndexedType());
-    uint64_t Size = TSize.getKnownMinValue() & PtrSizeMask;
     if (Constant *OpC = dyn_cast<Constant>(Op)) {
       if (OpC->isZeroValue())
         continue;
 
       // Handle a struct index, which adds its field offset to the pointer.
       if (StructType *STy = GTI.getStructTypeOrNull()) {
         uint64_t OpValue = OpC->getUniqueInteger().getZExtValue();
-        Size = DL.getStructLayout(STy)->getElementOffset(OpValue);
+        unsigned Size = DL.getStructLayout(STy)->getElementOffset(OpValue);
----------------
nikic wrote:

```suggestion
        uint64_t Size = DL.getStructLayout(STy)->getElementOffset(OpValue);
```

https://github.com/llvm/llvm-project/pull/71699