fix byval arguments in tail calls

Author: folkertdev

llvm/lib/Target/X86/X86ISelLoweringCall.cpp

@@ -2493,6 +2493,10 @@ X86TargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
     // would clobber.
     Chain = DAG.getStackArgumentTokenFactor(Chain);
 
+    if (ByValTempChain)
+      Chain =
+          DAG.getNode(ISD::TokenFactor, dl, MVT::Other, Chain, ByValTempChain);
+
     SmallVector<SDValue, 8> MemOpChains2;
     SDValue FIN;
     int FI = 0;
@@ -2536,12 +2540,12 @@ X86TargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
           NeedsStackCopy = !isTailCall;
         }
 
-        SDValue Source = DAG.getIntPtrConstant(VA.getLocMemOffset(), dl);
-        Source = DAG.getNode(ISD::ADD, dl, getPointerTy(DAG.getDataLayout()),
-                             ByValSrc, Source);
+        auto PtrVT = getPointerTy(DAG.getDataLayout());
+        SDValue DstAddr = DAG.getFrameIndex(FI, PtrVT);
 
-        MemOpChains2.push_back(
-            CreateCopyOfByValArgument(Source, FIN, Chain, Flags, DAG, dl));
+        // Copy the struct contents from ByValSrc to DstAddr.
+        MemOpChains2.push_back(CreateCopyOfByValArgument(
+            ByValSrc, DstAddr, Chain, Flags, DAG, dl));
       } else {
         // Store relative to framepointer.
         MemOpChains2.push_back(DAG.getStore(