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[Bug rtl-optimization/42621] [4.4 Regression] Computed gotos on AMD 800% slower
- From: "carlr at freemail dot gr" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 18 Jan 2010 13:14:35 -0000
- Subject: [Bug rtl-optimization/42621] [4.4 Regression] Computed gotos on AMD 800% slower
- References: <bug-42621-18630@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #10 from carlr at freemail dot gr 2010-01-18 13:14 -------
Please note that computed gotos are factored out because "they are a hell to
deal with" in tree-cfg.c:build_gimple_cfg(). This means that they MUST be
unfactored out as promised in the comment without leaving this to another
optimization step that may or may not be enabled.
Also, for our product there are 97 "extra jumps" and 95 of them are long jumps,
i.e:
12be0: ff e1 jmp *%ecx
...
12dda: e9 01 fe ff ff jmp 12be0 <main_loop+0x220>
...
so this is a serious both speed and size pessimisation :(
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42621