https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97585
Bug ID: 97585 Summary: Improve documentation for -march=x86-64 to say MMX, SSE, SSE2 are implied Product: gcc Version: 10.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: other Assignee: unassigned at gcc dot gnu.org Reporter: max at quendi dot de Target Milestone: --- The documentation at https://gcc.gnu.org/onlinedocs/gcc/x86-Options.html is pretty good when it comes to indicating which instruction set extensions are supported by which `march` value. But -march=x86-64 is an exception: It just states "A generic CPU with 64-bit extensions." but does not make it clear that this implies MMX, SSE, SSE2 (according to the content of gcc/common/config/i386/i386-common.c). This is only mentioned (as far as I could tell) in one place, indirectly, in the documentation for -mfpmath where it says: > For the x86-32 compiler, you must use -march=cpu-type, -msse or -msse2 > switches to enable SSE extensions and make this option effective. For the > x86-64 compiler, these extensions are enabled by default. I suggest to change > A generic CPU with 64-bit extensions. to something like this, matching the phrasing of other architectures like pentium4, nocona etc.: > A generic CPU with 64-bit extensions, MMX, SSE and SSE2 instruction set > support.