ConstantFolding: Don't crash when encountering vector GEP

[loladiro]

Summary

ConstantFolding tried to cast one of the scalar indices to a vector
type. Instead, use the vector type only for the first index (which
is the only one allowed to be a vector) and use its scalar type
otherwise.

Fixes PR31250.

[davide]

This seems is fixing the same problem of https://reviews.llvm.org/D26060
Probably I like your fix better, anyway, I'm happy as long as one of the two reviews land.

[majnemer]

LGTM

lib/Analysis/ConstantFolding.cpp

735–736

I believe this can be simplified to IntPtrScalarTy = IntPtrTy->getScalarType();

lib/Analysis/ConstantFolding.cpp

 }
 
 /// If array indices are not pointer-sized integers, explicitly cast them so
 /// that they aren't implicitly casted by the getelementptr.
 Constant *CastGEPIndices(Type *SrcElemTy, ArrayRef<Constant *> Ops,
                          Type *ResultTy, Optional<unsigned> InRangeIndex,
                          const DataLayout &DL, const TargetLibraryInfo *TLI) {
   Type *IntPtrTy = DL.getIntPtrType(ResultTy);
+  Type *IntPtrScalarTy =
+      IntPtrTy->isVectorTy() ? IntPtrTy->getScalarType() : IntPtrTy;
 
   bool Any = false;
   SmallVector<Constant*, 32> NewIdxs;
   for (unsigned i = 1, e = Ops.size(); i != e; ++i) {
     if ((i == 1 ||
-         !isa<StructType>(GetElementPtrInst::getIndexedType(SrcElemTy,
-             Ops.slice(1, i - 1)))) &&
-        Ops[i]->getType() != IntPtrTy) {
+         !isa<StructType>(GetElementPtrInst::getIndexedType(
+             SrcElemTy, Ops.slice(1, i - 1)))) &&
+        Ops[i]->getType() != (i == 1 ? IntPtrTy : IntPtrScalarTy)) {
       Any = true;
       NewIdxs.push_back(ConstantExpr::getCast(CastInst::getCastOpcode(Ops[i],
                                                                       true,
                                                                       IntPtrTy,
                                                                       true),
                                               Ops[i], IntPtrTy));
     } else
       NewIdxs.push_back(Ops[i]);

test/Analysis/ConstantFolding/vectorgep-crash.ll

+; RUN: opt -instcombine -S -o - %s | FileCheck %s
+; Tests that we don't crash upon encountering a vector GEP
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+%Dual = type { %Dual.72, %Partials.73 }
+%Dual.72 = type { double, %Partials }
+%Partials = type { [2 x double] }
+%Partials.73 = type { [2 x %Dual.72] }
+
+; Function Attrs: sspreq
+define <8 x i64*> @"julia_axpy!_65480"(%Dual* %arg1, <8 x i64> %arg2) {
+top:
+; CHECK: %VectorGep14 = getelementptr inbounds %Dual, %Dual* %arg1, <8 x i64> %arg2, i32 1, i32 0, i64 0, i32 1, i32 0, i64 0
+  %VectorGep14 = getelementptr inbounds %Dual, %Dual* %arg1, <8 x i64> %arg2, i32 1, i32 0, i64 0, i32 1, i32 0, i64 0
+  %0 = bitcast <8 x double*> %VectorGep14 to <8 x i64*>
+  ret <8 x i64*> %0
+}