[CaptureTracking] Treat vector GEPs as captures

Because AA does not support vectors of pointers, we have to
treat pointers that are inserted into a vector as captures. We
mostly already do so, but missed the case where getelementptr
is used to produce a vector.

Author: nikic

llvm/lib/Analysis/CaptureTracking.cpp

@@ -361,8 +361,13 @@ UseCaptureKind llvm::DetermineUseCaptureKind(
       return UseCaptureKind::MAY_CAPTURE;
     return UseCaptureKind::NO_CAPTURE;
   }
-  case Instruction::BitCast:
   case Instruction::GetElementPtr:
+    // AA does not support pointers of vectors, so GEP vector splats need to
+    // be considered as captures.
+    if (I->getType()->isVectorTy())
+      return UseCaptureKind::MAY_CAPTURE;
+    return UseCaptureKind::PASSTHROUGH;
+  case Instruction::BitCast:
   case Instruction::PHI:
   case Instruction::Select:
   case Instruction::AddrSpaceCast:

llvm/test/Transforms/GVN/captured-before.ll

@@ -133,15 +133,15 @@ loop:
   br label %loop
 }
 
-; FIXME: This is a miscompile.
 define i32 @test_splat_gep_capture(<1 x i32> %index) {
 ; CHECK-LABEL: define i32 @test_splat_gep_capture(
 ; CHECK-SAME: <1 x i32> [[INDEX:%.*]]) {
 ; CHECK-NEXT:    [[A:%.*]] = alloca i32, align 4
 ; CHECK-NEXT:    store i32 123, ptr [[A]], align 4
 ; CHECK-NEXT:    [[PTRS:%.*]] = getelementptr inbounds i32, ptr [[A]], <1 x i32> [[INDEX]]
 ; CHECK-NEXT:    call void @some_call(<1 x ptr> [[PTRS]])
-; CHECK-NEXT:    ret i32 123
+; CHECK-NEXT:    [[RELOAD:%.*]] = load i32, ptr [[A]], align 4
+; CHECK-NEXT:    ret i32 [[RELOAD]]
 ;
   %a = alloca i32
   store i32 123, ptr %a