[ConstraintElimination] Do not crash on vector GEP in decomposeGEP

[bjope]

Summary

Commit 359bc5c541ae4b02 caused
Assertion `isa<To>(Val) && "cast<Ty>() argument of incompatible type!"'
failures in decomposeGEP when the GEP pointer operand is a vector.

Fix is to use DataLayout::getIndexTypeSizeInBits when fetching the
index size, as it will use the scalar type in case of a ptr vector.

[fhahn]

Thanks! I'll extend the test coverage a bit.

llvm/lib/Transforms/Scalar/ConstraintElimination.cpp

 }
 
 static SmallVector<DecompEntry, 4>
 decomposeGEP(GetElementPtrInst &GEP,
              SmallVector<PreconditionTy, 4> &Preconditions, bool IsSigned,
              const DataLayout &DL) {
   // Do not reason about pointers where the index size is larger than 64 bits,
   // as the coefficients used to encode constraints are 64 bit integers.
-  unsigned AS =
-      cast<PointerType>(GEP.getPointerOperand()->getType())->getAddressSpace();
-  if (DL.getIndexSizeInBits(AS) > 64)
+  if (DL.getIndexTypeSizeInBits(GEP.getPointerOperand()->getType()) > 64)
     return {};
 
   if (!GEP.isInBounds())
     return {{0, nullptr}, {1, &GEP}};
 
   // Handle the (gep (gep ....), C) case by incrementing the constant
   // coefficient of the inner GEP, if C is a constant.
   auto *InnerGEP = dyn_cast<GetElementPtrInst>(GEP.getPointerOperand());

llvm/test/Transforms/ConstraintElimination/geps-ptrvector.ll

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -passes=constraint-elimination -S %s | FileCheck %s
+
+; Should not crash when GEP pointer operand is a vector.
+define <2 x i1> @test.vectorgep(<2 x ptr> %vec) {
+; CHECK-LABEL: @test.vectorgep(
+; CHECK-NEXT:    [[GEP:%.*]] = getelementptr inbounds i32, <2 x ptr> [[VEC:%.*]], i64 0
+; CHECK-NEXT:    [[COND:%.*]] = icmp ule <2 x ptr> [[GEP]], zeroinitializer
+; CHECK-NEXT:    ret <2 x i1> [[COND]]
+;
+  %gep = getelementptr inbounds i32, <2 x ptr> %vec, i64 0
+  %cond = icmp ule <2 x ptr> %gep, zeroinitializer
+  ret <2 x i1> %cond
+}