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[Bug target/47812] [x32] __builtin_strlen is miscompiled at -O2
- From: "xinliangli at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Sat, 19 Feb 2011 07:06:00 +0000
- Subject: [Bug target/47812] [x32] __builtin_strlen is miscompiled at -O2
- Auto-submitted: auto-generated
- References: <bug-47812-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47812
davidxl <xinliangli at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |xinliangli at gmail dot com
--- Comment #1 from davidxl <xinliangli at gmail dot com> 2011-02-19 07:05:47 UTC ---
There is a bug in the expand phase. Pseudo reg 59 is not initialized which
leads to an initialization to 0 by the init-reg pass. combine pass then happily
simply the comparison result with 1 which is returned.
The bad case with x32 where reg:SI 64 is initialized instead of 59:
insn 25 24 0 (parallel [
(set (reg:DI 64)
(minus:DI (reg:DI 64)
(reg:DI 62)))
(clobber (reg:CC 17 flags))
]) pr47812.c:5 -1
(nil))
;; return D.2771_2;
(insn 29 25 30 (set (reg:CCZ 17 flags)
(compare:CCZ (reg:SI 59 [ D.2772 ])
(const_int 3 [0x3]))) pr47812.c:5 -1
(nil))
The good case x86_64:
(insn 24 23 0 (parallel [
(set (reg:DI 59 [ D.2772 ])
(minus:DI (reg:DI 59 [ D.2772 ])
(reg:DI 62)))
(clobber (reg:CC 17 flags))
]) pr47812.c:5 -1
(nil))
;; return D.2771_2;
(insn 26 24 27 (set (reg:CCZ 17 flags)
(compare:CCZ (reg:DI 59 [ D.2772 ])
(const_int 3 [0x3]))) pr47812.c:5 -1
(nil))
David