http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44578
--- Comment #12 from Teresa Johnson <tejohnson at google dot com> 2013-04-30 05:43:06 UTC --- On Mon, Apr 29, 2013 at 10:37 AM, ubizjak at gmail dot com <gcc-bugzi...@gcc.gnu.org> wrote: > > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44578 > > --- Comment #10 from Uros Bizjak <ubizjak at gmail dot com> 2013-04-29 > 17:37:03 UTC --- > (In reply to comment #9) >> It does fix the issue I had in this test case. But theoretically can't >> this pattern still generate an MMX reference in some cases? And I see >> other instances of the same constraint in i386.md - is there a larger >> issue here and how can we prevent this? > > Yes, leaks of MMX registers were quite problematic in the past. A lot of > effort > went into insn patterns to balance register allocator to allow MMX registers > when necessary, and to avoid them otherwise. It looks that zero_extendsidi > pattern was skipped in these efforts. Thanks for the quick fix! > > -mno-mmx can be used to prevent MMX regs, but the allocator is quite well > tuned > nowadays, so instantiation of %mmX registers when not strictly needed will be > considered a bug. I found that due to the header file structure I cannot use -mno-mmx in certain cases - i.e. when including the STL <algorithm> header file and compiling with c++11. Is this a known issue/limitation? (after adding "#include <algorithm>" to the top of my test.cc test case): $ /usr/local/google/home/tejohnson/gcc_trunk_1_validate/bld-gcc/install/bin/g++ -O test.cc -g -S -std=c++11 -mno-mmx In file included from /usr/local/google/home/tejohnson/gcc_trunk_1_validate/bld-gcc/install/lib/gcc/x86_64-unknown-linux-gnu/4.9.0/include/xmmintrin.h:35:0, from /usr/local/google/home/tejohnson/gcc_trunk_1_validate/bld-gcc/install/lib/gcc/x86_64-unknown-linux-gnu/4.9.0/include/x86intrin.h:34, from /usr/local/google/home/tejohnson/gcc_trunk_1_validate/bld-gcc/install/include/c++/4.9.0/bits/opt_random.h:33, from /usr/local/google/home/tejohnson/gcc_trunk_1_validate/bld-gcc/install/include/c++/4.9.0/random:51, from /usr/local/google/home/tejohnson/gcc_trunk_1_validate/bld-gcc/install/include/c++/4.9.0/bits/stl_algo.h:65, from /usr/local/google/home/tejohnson/gcc_trunk_1_validate/bld-gcc/install/include/c++/4.9.0/algorithm:62, from test.cc:6: /usr/local/google/home/tejohnson/gcc_trunk_1_validate/bld-gcc/install/lib/gcc/x86_64-unknown-linux-gnu/4.9.0/include/mmintrin.h:31:3: error: #error "MMX instruction set not enabled" # error "MMX instruction set not enabled" ^ Thanks, Teresa > > -- > Configure bugmail: http://gcc.gnu.org/bugzilla/userprefs.cgi?tab=email > ------- You are receiving this mail because: ------- > You are on the CC list for the bug. -- Teresa Johnson | Software Engineer | tejohn...@google.com | 408-460-2413
