"Andrew Pinski" <[EMAIL PROTECTED]> дÈëÏûÏ¢ÐÂÎÅ:[EMAIL PROTECTED] > On 15 Mar 2007 08:12:21 -0700, Ian Lance Taylor <[EMAIL PROTECTED]> wrote: >> Galloth <[EMAIL PROTECTED]> writes: >> >> > I want ask, if there is posibilities that gcc will be automaticaly >> > generates MMX instruction? I tried -mtune, -march -mmmx. But gcc stil >> > generates code without MMX instruction. On net I found only >> > information about inline assembler function or citation from man page. >> > I tried to compile program for adding two arrays of 24 chars. >> >> This question is appropriate for the mailing list >> [EMAIL PROTECTED], not for [EMAIL PROTECTED] Please take any >> follow-ups to gcc-help. Thanks. > > Actually this one I think belongs still here because ... > >> In some cases gcc may be able to automatically generate MMX >> instructions if you use the -ftree-vectorize option. > > This is not true right now. GCC is not able to automatically use the > MMX instructions at all, this is already filed as PR 22076 and others. > There was a patch posted as an RFC to fix this but it caused > regression on x86_64 and the person who submitted has not updated it > yet for the mainline.
I remembered that Uros said that the biggest problem is to determine which mode (x87 or MMX) is active; MMX/3DNow! autovectorization isn't so useful when SSE2/SSE is available so maybe we can turn it off with x86_64? -- Zuxy
