Well, I don't know much about what Clang will actually do here, but I'll follow your advice and add -O0 and pipe to opt -S -mem2reg. I'll also add a test case in LLVM (test/CodeGen/PowerPC) that will test that after opt and llc, we generate the desired code for these builtins.
Thanks Sanjay and Bjorn. On Wed, Sep 28, 2016 at 6:53 PM, Sanjay Patel <spa...@rotateright.com> wrote: > spatel added a comment. > > In https://reviews.llvm.org/D24397#555552, @nemanjai wrote: > > > In https://reviews.llvm.org/D24397#555470, @spatel wrote: > > > > > Having a clang regression/unit test that depends on optimizer behavior > is generally viewed as wrong. Can the tests be split into front-end (clang) > tests and separate tests for the IR optimizer? Both x86 and AArch64 have > done something like that in the last few months for testing of > builtins/intrinsics. > > > > > > Yeah, that sounds reasonable. I'll remove the -O2 from the test case and > remove the checks for the select instructions. That's really the only major > difference. So am I to understand the nsw/nuw flags will not be added > without -O2 and the aforementioned changes will suffice? > > > Changing to -O0 or using -disable-llvm-optzns should keep the clang tests > from breaking due to underlying changes in the IR optimizer. That may lead > to a lot of bloat though. In http://lists.llvm.org/ > pipermail/cfe-commits/Week-of-Mon-20160307/152324.html , it was viewed as > ok, if not ideal, to pipe the clang IR output using "opt -S -mem2reg". > > Note that clang itself uses APIs like IRBuilder::CreateNUWSub(), so I > think it's possible to see no-wrap IR even without the IR optimizer kicking > in (but probably isn't a concern in this case?). > > > Repository: > rL LLVM > > https://reviews.llvm.org/D24397 > > > >
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