Prevent tailcallelim from breaking "recursive" calls to builtins.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@41804 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/TailRecursionElimination.cpp b/lib/Transforms/Scalar/TailRecursionElimination.cpp
index 497b81f..7eb47dd 100644
--- a/lib/Transforms/Scalar/TailRecursionElimination.cpp
+++ b/lib/Transforms/Scalar/TailRecursionElimination.cpp
@@ -302,6 +302,15 @@
if (&BB->front() == Ret) // Make sure there is something before the ret...
return false;
+
+ // If the return is in the entry block, then making this transformation would
+ // turn infinite recursion into an infinite loop. This transformation is ok
+ // in theory, but breaks some code like:
+ // double fabs(double f) { return __builtin_fabs(f); } // a 'fabs' call
+ // disable this xform in this case, because the code generator will lower the
+ // call to fabs into inline code.
+ if (BB == &F->getEntryBlock())
+ return false;
// Scan backwards from the return, checking to see if there is a tail call in
// this block. If so, set CI to it.