[LLVMbugs] [Bug 9010] New: Function parameter corruption when using tail call optimization in Windows 64

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=9010

           Summary: Function parameter corruption when using tail call
                    optimization in Windows 64
           Product: libraries
           Version: trunk
          Platform: PC
        OS/Version: Windows XP
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: X86
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: artiom.myaskouvskey at intel.com
                CC: llvmbugs at cs.uiuc.edu


Created an attachment (id=6028)
 --> (http://llvm.org/bugs/attachment.cgi?id=6028)
.ll and generated .s file

Tail call optimization is erroneously applied in Windows 64.
As result stack area which contains function parameters is released (RSP is
updated) before the call (replaced by jump in tail call optimization). It may
cause to wrong function behavior. See attached .s example. Specifically these 3
lines may explain the problem:

lea    R8, QWORD PTR [RSP + 32] ; using stack to for parameter storage
...
add    RSP, 232  ;; Stack is freed and allocated parameter with it
jmp    testcall                # TAILCALL


Attached are .ll and .s file generated with latest llc.

The simple inlined fix is solves the problem.

Index: lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- lib/Target/X86/X86ISelLowering.cpp    (revision 2609)
+++ lib/Target/X86/X86ISelLowering.cpp    (working copy)
@@ -2501,6 +2501,9 @@
     SmallVector<CCValAssign, 16> ArgLocs;
     CCState CCInfo(CalleeCC, isVarArg, getTargetMachine(),
                    ArgLocs, *DAG.getContext());
+    if (Subtarget->isTargetWin64()) {  
+      CCInfo.AllocateStack(32, 8); 
+    }
     CCInfo.AnalyzeCallOperands(Outs, CCAssignFnForNode(CalleeCC));
     if (CCInfo.getNextStackOffset()) {
       MachineFunction &MF = DAG.getMachineFunction();

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