Correction to tail call optimization code. The new return address

was stored to the acutal stack slot before the parameters were
lowered to their stack slot. This could cause arguments to be
overwritten by the return address if the called function had less
parameters than the caller function. The update should remove the
last failing test case of llc-beta: SPASS.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@43027 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 19 insertions, 11 deletions

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 8726c587ca..53bb81dd30 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -707,10 +707,11 @@ SDOperand X86TargetLowering::LowerRET(SDOperand Op, SelectionDAG &DAG) {
     Operands.push_back(StackAdjustment);
     // Copy registers used by the call. Last operand is a flag so it is not
     // copied.
-    for(unsigned i=3; i < TailCall.getNumOperands()-1;i++) {
+    for (unsigned i=3; i < TailCall.getNumOperands()-1; i++) {
       Operands.push_back(Chain.getOperand(i));
     }
-    return DAG.getNode(X86ISD::TC_RETURN, MVT::Other, &Operands[0], Operands.size()); 
+    return DAG.getNode(X86ISD::TC_RETURN, MVT::Other, &Operands[0], 
+                       Operands.size());
   }
   
   // Regular return.
@@ -1520,23 +1521,25 @@ SDOperand X86TargetLowering::LowerX86_TailCallTo(SDOperand Op,
   if (FPDiff < (MF.getInfo<X86MachineFunctionInfo>()->getTCReturnAddrDelta()))
     MF.getInfo<X86MachineFunctionInfo>()->setTCReturnAddrDelta(FPDiff);
 
-  // Adjust the ret address stack slot.
+  Chain = DAG.
+   getCALLSEQ_START(Chain, DAG.getConstant(NumBytesToBePushed, getPointerTy()));
+
+  // Adjust the Return address stack slot.
+  SDOperand RetAddrFrIdx, NewRetAddrFrIdx;
   if (FPDiff) {
     MVT::ValueType VT = is64Bit ? MVT::i64 : MVT::i32;
-    SDOperand RetAddrFrIdx = getReturnAddressFrameIndex(DAG); 
+    RetAddrFrIdx = getReturnAddressFrameIndex(DAG);
+    // Load the "old" Return address.
     RetAddrFrIdx = 
-      DAG.getLoad(VT, DAG.getEntryNode(),RetAddrFrIdx, NULL, 0);
-    // Emit a store of the saved ret value to the new location.
+      DAG.getLoad(VT, Chain,RetAddrFrIdx, NULL, 0);
+    // Calculate the new stack slot for the return address.
     int SlotSize = is64Bit ? 8 : 4;
     int NewReturnAddrFI = 
       MF.getFrameInfo()->CreateFixedObject(SlotSize, FPDiff-SlotSize);
-    SDOperand NewRetAddrFrIdx = DAG.getFrameIndex(NewReturnAddrFI, VT);
-    Chain = DAG.getStore(Chain,RetAddrFrIdx, NewRetAddrFrIdx, NULL, 0);
+    NewRetAddrFrIdx = DAG.getFrameIndex(NewReturnAddrFI, VT);
+    Chain = SDOperand(RetAddrFrIdx.Val, 1);
   }
 
-  Chain = DAG.
-   getCALLSEQ_START(Chain, DAG.getConstant(NumBytesToBePushed, getPointerTy()));
-
   SmallVector<std::pair<unsigned, SDOperand>, 8> RegsToPass;
   SmallVector<SDOperand, 8> MemOpChains;
   SmallVector<SDOperand, 8> MemOpChains2;
@@ -1592,6 +1595,7 @@ SDOperand X86TargetLowering::LowerX86_TailCallTo(SDOperand Op,
     InFlag = Chain.getValue(1);
   }
   InFlag = SDOperand();
+
   // Copy from stack slots to stack slot of a tail called function. This needs
   // to be done because if we would lower the arguments directly to their real
   // stack slot we might end up overwriting each other.
@@ -1637,6 +1641,10 @@ SDOperand X86TargetLowering::LowerX86_TailCallTo(SDOperand Op,
     Chain = DAG.getNode(ISD::TokenFactor, MVT::Other,
                         &MemOpChains2[0], MemOpChains.size());
 
+  // Store the return address to the appropriate stack slot.
+  if (FPDiff)
+    Chain = DAG.getStore(Chain,RetAddrFrIdx, NewRetAddrFrIdx, NULL, 0);
+
   // ELF / PIC requires GOT in the EBX register before function calls via PLT
   // GOT pointer.
   // Does not work with tail call since ebx is not restored correctly by