https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107172
H.J. Lu <hjl.tools at gmail dot com> changed:
What |Removed |Added
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CC| |hjl.tools at gmail dot com,
| |ubizjak at gmail dot com
--- Comment #4 from H.J. Lu <hjl.tools at gmail dot com> ---
There are:
(insn 6 5 17 2 (set (reg:SI 87 [ a_lsm.8 ])
(const_int 2 [0x2])) "x.c":7:7 83 {*movsi_internal}
(nil))
...
(insn 62 59 63 2 (parallel [
(set (reg:CCC 17 flags)
(ne:CCC (reg:SI 87 [ a_lsm.8 ])
(const_int 0 [0])))
(set (reg:SI 96)
(neg:SI (reg:SI 87 [ a_lsm.8 ])))
]) "x.c":4:7 680 {*negsi_ccc_1}
(expr_list:REG_DEAD (reg:SI 87 [ a_lsm.8 ])
(expr_list:REG_UNUSED (reg:SI 96)
(nil))))
(insn 63 62 64 2 (parallel [
(set (reg:SI 97)
(neg:SI (ltu:SI (reg:CCC 17 flags)
(const_int 0 [0]))))
(clobber (reg:CC 17 flags))
]) "x.c":4:7 1258 {*x86_movsicc_0_m1_neg}
(expr_list:REG_DEAD (reg:CCC 17 flags)
(expr_list:REG_UNUSED (reg:CC 17 flags)
(nil))))
Since r87 == 2, combine knows (reg:CCC 17 flags) == 1 and optimizes
(ltu:SI (reg:CCC 17 flags)
(const_int 0 [0]))
as
(ltu:SI (const_int 1 [1])
(const_int 0 [0]))
to 0.
