3 ms·

At the very least, can check when the target isn't a basic block and thus it's a clear win. Will fix your case. I'm dubious about the whole thing though. Seems

At the very least, can check when the target isn't a basic block and thus it's a clear win. Will fix your case. I'm dubious about the whole thing though. Seems like it may day from when branching "down" vs. "up" mattered to branch prediction.

pyler 5y ago
It seems that that code handles just the case when target is function. https://github.com/llvm/llvm-project/blob/535df472b04208d6ae88e017c8f1d831fb239346/llvm/lib/Target/X86/X86InstrInfo.cpp#L2870 https://github.com/llvm/llvm-project/blob/535df472b04208d6ae...
ndesaulniers 5y ago
commit a468601e0ead ("[X86] Re-enable conditional tail calls and fix PR31257.") https://reviews.llvm.org/D29856 https://reviews.llvm.org/D29856 added the comment. If I remove the check for `OptForSize` and `PredTBB == MBB`, we can optimize OP's report, but seem to regress basic tests like llvm/test/CodeGen/X86/conditional-tailcall.ll, literally flipping the branches incorrectly IIUC. Filed: https://bugs.llvm.org/show_bug.cgi?id=50130 https://bugs.llvm.org/show_bug.cgi?id=50130