fix rdar://7590304, a miscompilation of objc apps on arm. The caller

of objc message send was getting marked arm_apcscc, but the prototype
isn't.  This is fine at runtime because objcmsgsend is implemented in
assembly.  Only turn a mismatched caller and callee into 'unreachable'
if the callee is a definition.

llvm-svn: 94986

1 files changed, 7 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 9c420c83873..5de846e90cf 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -692,10 +692,14 @@ Instruction *InstCombiner::visitCallSite(CallSite CS) {
   Value *Callee = CS.getCalledValue();
 
   if (Function *CalleeF = dyn_cast<Function>(Callee))
-    if (CalleeF->getCallingConv() != CS.getCallingConv()) {
+    // If the call and callee calling conventions don't match, this call must
+    // be unreachable, as the call is undefined.
+    if (CalleeF->getCallingConv() != CS.getCallingConv() &&
+        // Only do this for calls to a function with a body.  A prototype may
+        // not actually end up matching the implementation's calling conv for a
+        // variety of reasons (e.g. it may be written in assembly).
+        !CalleeF->isDeclaration()) {
       Instruction *OldCall = CS.getInstruction();
-      // If the call and callee calling conventions don't match, this call must
-      // be unreachable, as the call is undefined.
       new StoreInst(ConstantInt::getTrue(Callee->getContext()),
                 UndefValue::get(Type::getInt1PtrTy(Callee->getContext())), 
                                   OldCall);