Index: llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -10616,9 +10616,9 @@
     DenseMap<int, int> &ArgCopyElisionFrameIndexMap,
     SmallPtrSetImpl<const Instruction *> &ElidedArgCopyInstrs,
     ArgCopyElisionMapTy &ArgCopyElisionCandidates, const Argument &Arg,
-    SDValue ArgVal, bool &ArgHasUses) {
+    ArrayRef<SDValue> ArgVals, bool &ArgHasUses) {
   // Check if this is a load from a fixed stack object.
-  auto *LNode = dyn_cast<LoadSDNode>(ArgVal);
+  auto *LNode = dyn_cast<LoadSDNode>(ArgVals[0]);
   if (!LNode)
     return;
   auto *FINode = dyn_cast<FrameIndexSDNode>(LNode->getBasePtr().getNode());
@@ -10661,7 +10661,8 @@
   MFI.setIsImmutableObjectIndex(FixedIndex, false);
   AllocaIndex = FixedIndex;
   ArgCopyElisionFrameIndexMap.insert({OldIndex, FixedIndex});
-  Chains.push_back(ArgVal.getValue(1));
+  for (SDValue ArgVal : ArgVals)
+    Chains.push_back(ArgVal.getValue(1));
 
   // Avoid emitting code for the store implementing the copy.
   const StoreInst *SI = ArgCopyIter->second.second;
@@ -10922,9 +10923,14 @@
     // Elide the copying store if the target loaded this argument from a
     // suitable fixed stack object.
     if (Ins[i].Flags.isCopyElisionCandidate()) {
+      unsigned NumParts = 0;
+      for (EVT VT : ValueVTs)
+        NumParts += TLI->getNumRegistersForCallingConv(*CurDAG->getContext(),
+                                                       F.getCallingConv(), VT);
+
       tryToElideArgumentCopy(*FuncInfo, Chains, ArgCopyElisionFrameIndexMap,
                              ElidedArgCopyInstrs, ArgCopyElisionCandidates, Arg,
-                             InVals[i], ArgHasUses);
+                             ArrayRef(&InVals[i], NumParts), ArgHasUses);
     }
 
     // If this argument is unused then remember its value. It is used to generate
Index: llvm/test/CodeGen/X86/pr63430.ll
===================================================================
--- llvm/test/CodeGen/X86/pr63430.ll
+++ llvm/test/CodeGen/X86/pr63430.ll
@@ -1,14 +1,14 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --no_x86_scrub_sp --version 2
 ; RUN: llc -mtriple=x86_64-unknown-linux < %s | FileCheck %s
 
-; TODO: This is a miscompile.
+; Make sure the argument is read before the stack slot is over-written.
 define i1 @test(ptr %a0, ptr %a1, ptr %a2, ptr %a3, ptr %a4, ptr %a5, i128 %x) {
 ; CHECK-LABEL: test:
 ; CHECK:       # %bb.0:
 ; CHECK-NEXT:    movq 8(%rsp), %rax
 ; CHECK-NEXT:    xorps %xmm0, %xmm0
-; CHECK-NEXT:    movaps %xmm0, 8(%rsp)
 ; CHECK-NEXT:    andq 16(%rsp), %rax
+; CHECK-NEXT:    movaps %xmm0, 8(%rsp)
 ; CHECK-NEXT:    cmpq $-1, %rax
 ; CHECK-NEXT:    sete %al
 ; CHECK-NEXT:    retq