https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69377
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Priority|P3 |P1
CC| |vmakarov at gcc dot gnu.org
--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Looks like a RA bug to me.
At least in *.ira we have above the test for the second printf:
(insn 171 170 316 24 (set (reg/v:QI 122 [ x ])
(not:QI (subreg:QI (reg:SI 201) 0))) pr69377.c:64 504 {*one_cmplqi2_1}
(expr_list:REG_DEAD (reg:SI 201)
(nil)))
(insn 316 171 172 24 (set (reg:HI 224 [ u.3_64 ])
(mem/c:HI (symbol_ref:SI ("u") [flags 0x2] <var_decl 0x7fefb81f2120
u>) [2 u+0 S2 A16])) 88 {*movhi_internal}
(nil))
(insn 172 316 173 24 (set (reg:CCGC 17 flags)
(compare:CCGC (reg/v:QI 156 [ x ])
(reg/v:QI 122 [ x ]))) pr69377.c:65 5 {*cmpqi_1}
(expr_list:REG_DEAD (reg/v:QI 156 [ x ])
(nil)))
(jump_insn 173 172 174 24 (set (pc)
(if_then_else (le (reg:CCGC 17 flags)
(const_int 0 [0]))
(label_ref:SI 180)
(pc))) pr69377.c:65 633 {*jcc_1}
(expr_list:REG_DEAD (reg:CCGC 17 flags)
(int_list:REG_BR_PROB 7100 (nil)))
-> 180)
but *.reload turns it into:
(insn 457 170 171 26 (set (reg/v:QI 0 ax [orig:122 x ] [122])
(reg:QI 1 dx [201])) pr69377.c:64 89 {*movqi_internal}
(nil))
(insn 171 457 458 26 (set (reg/v:QI 0 ax [orig:122 x ] [122])
(not:QI (reg/v:QI 0 ax [orig:122 x ] [122]))) pr69377.c:64 504
{*one_cmplqi2_1}
(nil))
(insn 458 171 509 26 (set (reg/v:QI 1 dx [orig:156 x ] [156])
(reg/v:QI 0 ax [orig:122 x ] [122])) pr69377.c:64 89 {*movqi_internal}
(nil))
(insn 509 458 316 26 (set (mem/c:QI (plus:SI (reg/f:SI 7 sp)
(const_int 8 [0x8])) [5 %sfp+-24 S1 A32])
(reg/v:QI 1 dx [orig:156 x ] [156])) pr69377.c:64 89 {*movqi_internal}
(nil))
(insn 316 509 499 26 (set (reg:HI 0 ax [orig:224 u.3_64 ] [224])
(mem/c:HI (symbol_ref:SI ("u") [flags 0x2] <var_decl 0x7fefb81f2120
u>) [2 u+0 S2 A16])) 88 {*movhi_internal}
(nil))
(insn 499 316 172 26 (set (reg/v:QI 3 bx [orig:156 x ] [156])
(reg/v:QI 1 dx [orig:156 x ] [156])) pr69377.c:65 89 {*movqi_internal}
(nil))
(insn 172 499 173 26 (set (reg:CCGC 17 flags)
(compare:CCGC (reg/v:QI 3 bx [orig:156 x ] [156])
(reg/v:QI 3 bx [orig:156 x ] [156]))) pr69377.c:65 5 {*cmpqi_1}
(nil))
(jump_insn 173 172 174 26 (set (pc)
(if_then_else (le (reg:CCGC 17 flags)
(const_int 0 [0]))
(label_ref:SI 180)
(pc))) pr69377.c:65 633 {*jcc_1}
(int_list:REG_BR_PROB 7100 (nil))
-> 180)
Thus in the end we compare a QImode register with itself, while the source has:
c = x;
z = -y;
t1 = (j && y << c) + k || x;
x = ~(u % p);
if (x < c)
and thus we want to compare the older value of x with completely different
value.
