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[Bug c++/37922] [4.4 Regression] code generation error
- From: "jakub at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 16 Dec 2008 15:05:19 -0000
- Subject: [Bug c++/37922] [4.4 Regression] code generation error
- References: <bug-37922-3137@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #13 from jakub at gcc dot gnu dot org 2008-12-16 15:05 -------
Not doing this optimization if added_clobbers_hard_reg_p would basically kill
it on i386/x86_64 except for constant values, all the shifts clobber hard
registers. But typically flags register is only live for very short range
between compare and (usually the next insn) following conditional jump. Given
how many insns clobber the flags it is very rare to have the setter and user
many insns appart.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37922