ARM: tail-call inside a function where part of a byval argument is on caller's

local frame causes problem.

For example:
void f(StructToPass s) {
  g(&s, sizeof(s));
}
will cause problem with tail-call since part of s is passed via registers and
saved in f's local frame. When g tries to access s, part of s may be corrupted
since f's local frame is popped out before the tail-call.

The current fix is to disable tail-call if getVarArgsRegSaveSize is not 0 for
the caller. This is a conservative approach, if we can prove the address of
s or part of s is not taken and passed to g, it should be okay to perform
tail-call.

rdar://12442472


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165853 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 8 insertions, 0 deletions

diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index bd0c659414..21e7e98c85 100644
--- a/lib/Target/ARM/ARMISelLowering.cpp
+++ b/lib/Target/ARM/ARMISelLowering.cpp
@@ -1804,6 +1804,14 @@ ARMTargetLowering::IsEligibleForTailCallOptimization(SDValue Callee,
     }
   }
 
+  // If Caller's vararg or byval argument has been split between registers and
+  // stack, do not perform tail call, since part of the argument is in caller's
+  // local frame.
+  const ARMFunctionInfo *AFI_Caller = DAG.getMachineFunction().
+                                      getInfo<ARMFunctionInfo>();
+  if (AFI_Caller->getVarArgsRegSaveSize())
+    return false;
+
   // If the callee takes no arguments then go on to check the results of the
   // call.
   if (!Outs.empty()) {