Index: llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
===================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -3408,8 +3408,15 @@
 
   // Turn icmp (ptrtoint x), (ptrtoint/c) into a compare of the input if the
   // integer type is the same size as the pointer type.
+  const auto& CompatibleSizes = [&](Type* SrcTy, Type* DestTy) -> bool {
+    if (isa<VectorType>(SrcTy)) {
+      SrcTy = cast<VectorType>(SrcTy)->getElementType();
+      DestTy = cast<VectorType>(DestTy)->getElementType();
+    }
+    return DL.getPointerTypeSizeInBits(SrcTy) == DestTy->getIntegerBitWidth();
+  };
   if (LHSCI->getOpcode() == Instruction::PtrToInt &&
-      DL.getPointerTypeSizeInBits(SrcTy) == DestTy->getIntegerBitWidth()) {
+      CompatibleSizes(SrcTy, DestTy)) {
     Value *RHSOp = nullptr;
     if (auto *RHSC = dyn_cast<PtrToIntOperator>(ICmp.getOperand(1))) {
       Value *RHSCIOp = RHSC->getOperand(0);
Index: llvm/trunk/test/Transforms/InstCombine/icmp.ll
===================================================================
--- llvm/trunk/test/Transforms/InstCombine/icmp.ll
+++ llvm/trunk/test/Transforms/InstCombine/icmp.ll
@@ -3302,3 +3302,15 @@
   ret i1 %cmp
 }
 
+; Don't crash by assuming the compared values are integers.
+define <2 x i1> @PR36583(<2 x i8*>)  {
+; CHECK-LABEL: @PR36583(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[RES:%.*]] = icmp eq <2 x i8*> %0, zeroinitializer
+; CHECK-NEXT:    ret <2 x i1> [[RES]]
+;
+entry:
+  %cast = ptrtoint <2 x i8*> %0 to <2 x i64>
+  %res = icmp eq <2 x i64> %cast, zeroinitializer
+  ret <2 x i1> %res
+}