diff options
| -rw-r--r-- | lib/Transforms/Scalar/TailRecursionElimination.cpp | 9 | ||||
| -rw-r--r-- | test/Transforms/TailCallElim/inf-recursion.ll | 10 |
2 files changed, 19 insertions, 0 deletions
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 @@ bool TailCallElim::ProcessReturningBlock(ReturnInst *Ret, BasicBlock *&OldEntry, 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. diff --git a/test/Transforms/TailCallElim/inf-recursion.ll b/test/Transforms/TailCallElim/inf-recursion.ll new file mode 100644 index 0000000..d346171 --- /dev/null +++ b/test/Transforms/TailCallElim/inf-recursion.ll @@ -0,0 +1,10 @@ +; RUN: llvm-as < %s | opt -tailcallelim | grep call +; Don't turn this into an infinite loop, this is probably the implementation +; of fabs and we expect the codegen to lower fabs. + +define double @fabs(double %f) { +entry: + %tmp2 = call double @fabs( double %f ) ; <double> [#uses=1] + ret double %tmp2 +} + |