Let StructRetPromotion check if it's users are really calling it and not

passing its pointer. Fixes test with added testcase.

llvm-svn: 51991

llvm/lib/Transforms/IPO/StructRetPromotion.cpp

@@ -158,6 +158,10 @@ bool SRETPromotion::isSafeToUpdateAllCallers(Function *F) {
 
   for (Value::use_iterator FnUseI = F->use_begin(), FnUseE = F->use_end();
        FnUseI != FnUseE; ++FnUseI) {
+    // The function is passed in as an argument to (possibly) another function,
+    // we can't change it!
+    if (FnUseI.getOperandNo() != 0)
+      return false;
 
     CallSite CS = CallSite::get(*FnUseI);
     Instruction *Call = CS.getInstruction();

llvm/test/Transforms/SRETPromotion/2008-06-04-function-pointer-passing.ll

@@ -0,0 +1,24 @@
+; This test lures sretpromotion into promoting the sret argument of foo, even
+; when the function is used as an argument to bar. It used to not check for
+; this, assuming that all users of foo were direct calls, resulting in an
+; assertion failure later on.
+
+; We're mainly testing for opt not to crash, but we'll check to see if the sret
+; attribute is still there for good measure.
+; RUN: llvm-as < %s | opt -sretpromotion | llvm-dis | grep sret
+
+%struct.S = type <{ i32, i32 }>
+
+define i32 @main() {
+entry:
+	%tmp = alloca %struct.S		; <%struct.S*> [#uses=1]
+	call void @bar( %struct.S* sret  %tmp, void (%struct.S*, ...)* @foo )
+	ret i32 undef
+}
+
+declare void @bar(%struct.S* sret , void (%struct.S*, ...)*)
+
+define internal void @foo(%struct.S* sret  %agg.result, ...) {
+entry:
+	ret void
+}