craig.topper added inline comments.
================ Comment at: clang/lib/Basic/Targets/X86.cpp:159 + // Enable CRC32 if SSE4.2 is enabled. + // NOTE: In conformance with GCC behavior, CRC32 is still available even if + // it's explicitly disabled. ---------------- hjl.tools wrote: > tianqing wrote: > > craig.topper wrote: > > > This doesn't seem to be true. It causes gcc to crash. > > > https://godbolt.org/z/39rEbsejh > > Well I was using GCC 11.1, it compiles. > > > > The way I see it, crash means a bug (not surprising since it's trunk), and > > can be interpreted as incompletely defined behavior until it's fixed. > > > > Some tests on GCC trunk: > > 1. -msse4.2: Pass - sse4.2 enables crc32. > > 2. -mcrc32 -mno-sse4.2: Pass - no-sse4.2 doesn't disable crc32. > > 3. -msse4.2 -mno-sse4.2: Error - no-sse4.2 disables crc32. > > 4. -mno-crc32 -msse4.2: Crash - undefined behavior > > 5. -msse4.2 -mno-crc32: Crash - undefined behavior > > > > > > It's hard to extract some consistent underlying logic from the GCC results. > I posted a patch: > https://gcc.gnu.org/pipermail/gcc-patches/2021-July/575741.html @hjl.tools does that turn the crash into making -mno-crc32 into making crc32 instruction disabled? Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D105462/new/ https://reviews.llvm.org/D105462 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
