[SLPVectorizer][OpaquePtrs] Check GEP source element type

[aeubanks]

Summary

Fixes a miscompile with opaque pointers.

[nikic]

LGTM

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

case Instruction::GetElementPtr: {
           newTreeEntry(VL, None /*not vectorized*/, S, UserTreeIdx,
                        ReuseShuffleIndicies);
           return;
         }
       }
 
       // We can't combine several GEPs into one vector if they operate on
       // different types.
-      Type *Ty0 = VL0->getOperand(0)->getType();
+      Type *Ty0 = cast<GEPOperator>(VL0)->getSourceElementType();
       for (Value *V : VL) {
-        Type *CurTy = cast<Instruction>(V)->getOperand(0)->getType();
+        Type *CurTy = cast<GEPOperator>(V)->getSourceElementType();
         if (Ty0 != CurTy) {
           LLVM_DEBUG(dbgs()
                      << "SLP: not-vectorizable GEP (different types).\n");
           BS.cancelScheduling(VL, VL0);
           newTreeEntry(VL, None /*not vectorized*/, S, UserTreeIdx,
                        ReuseShuffleIndicies);
           return;
         }

llvm/test/Transforms/SLPVectorizer/X86/opaque-ptr-2.ll

 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt -S -slp-vectorizer -opaque-pointers < %s | FileCheck %s
 
 target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 define void @test(ptr %arg, ptr %arg1, ptr %arg2) {
 ; CHECK-LABEL: @test(
-; CHECK-NEXT:    [[TMP1:%.*]] = insertelement <2 x ptr> poison, ptr [[ARG1:%.*]], i32 0
-; CHECK-NEXT:    [[TMP2:%.*]] = insertelement <2 x ptr> [[TMP1]], ptr [[ARG2:%.*]], i32 1
-; CHECK-NEXT:    [[TMP3:%.*]] = getelementptr ptr, <2 x ptr> [[TMP2]], <2 x i64> <i64 -1, i64 128>
+; CHECK-NEXT:    [[TMP:%.*]] = getelementptr inbounds i8, ptr [[ARG2:%.*]], i64 128
+; CHECK-NEXT:    [[TMP3:%.*]] = getelementptr inbounds ptr, ptr [[ARG1:%.*]], i64 -1
 ; CHECK-NEXT:    [[TMP4:%.*]] = getelementptr inbounds ptr, ptr [[ARG:%.*]], i64 0
 ; CHECK-NEXT:    [[TMP5:%.*]] = getelementptr inbounds ptr, ptr [[ARG]], i64 1
-; CHECK-NEXT:    store <2 x ptr> [[TMP3]], ptr [[TMP4]], align 8
+; CHECK-NEXT:    store ptr [[TMP3]], ptr [[TMP4]], align 8
+; CHECK-NEXT:    store ptr [[TMP]], ptr [[TMP5]], align 8
 ; CHECK-NEXT:    ret void
 ;
   %tmp = getelementptr inbounds i8, ptr %arg2, i64 128
   %tmp3 = getelementptr inbounds ptr, ptr %arg1, i64 -1
   %tmp4 = getelementptr inbounds ptr, ptr %arg, i64 0
   %tmp5 = getelementptr inbounds ptr, ptr %arg, i64 1
   store ptr %tmp3, ptr %tmp4, align 8
   store ptr %tmp, ptr %tmp5, align 8
   ret void
 }