https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115927
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |law at gcc dot gnu.org
Status|UNCONFIRMED |NEW
Ever confirmed|0 |1
Last reconfirmed| |2024-07-14
Version|unknown |15.0
Target Milestone|--- |15.0
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
What is missing between 14 and 15 is:
xor edx, edx
is due to ext_dce does:
Processing insn:
13: r116:SI=zero_extend(r117:QI)
REG_DEAD r117:QI
Trying to simplify pattern:
(zero_extend:SI (reg:QI 117))
rescanning insn with uid = 13.
Successfully transformed to:
(subreg:SI (reg:QI 117) 0)
Which originally comes from:
(insn 12 11 13 2 (set (reg:QI 117)
(ne:QI (reg:CCZ 17 flags)
(const_int 0 [0]))) "/app/example.cpp":8:25 1241 {*setcc_qi}
(expr_list:REG_DEAD (reg:CCZ 17 flags)
(nil)))
(insn 13 12 14 2 (set (reg:SI 116 [ _6 ])
(subreg:SI (reg:QI 117) 0)) "/app/example.cpp":8:25 89
{*movsi_internal}
(expr_list:REG_DEAD (reg:QI 117)
(nil)))
But the set QI here does not set the full register; it only touches the lower
part so the zero_extend is still needed.
