https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68217
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Known to fail| |4.1.2, 4.3.5
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fails with just -O1 as well, --param max-combine-insns=2 "fixes" it, =3
"fails".
Thus it's triggered by a 3-insn combine:
Trying 9 -> 10:
Successfully matched this instruction:
(set (reg:CCNO 17 flags)
(compare:CCNO (and:DI (reg:DI 91 [ D.1848 ])
(reg:DI 93))
(const_int 0 [0])))
allowing combination of insns 9 and 10
original costs 4 + 4 = 8
Trying 7, 8 -> 10:
Successfully matched this instruction:
(set (reg:CCZ 17 flags)
(compare:CCZ (zero_extract:DI (subreg:DI (reg:SI 87 [ D.1847 ]) 0)
(const_int 1 [0x1])
(const_int 31 [0x1f]))
(const_int 0 [0])))
Successfully matched this instruction:
(set (pc)
(if_then_else (eq (reg:CCZ 17 flags)
(const_int 0 [0]))
(label_ref 15)
(pc)))
allowing combination of insns 7, 8 and 10
original costs 4 + 3 + 8 = 0
replacement cost 4
Before:
(insn 7 6 8 2 (set (reg:DI 91 [ D.1848 ])
(sign_extend:DI (reg:SI 87 [ D.1847 ]))) t.c:5 142 {*extendsidi2_rex64}
(expr_list:REG_DEAD (reg:SI 87 [ D.1847 ])
(nil)))
(insn 8 7 9 2 (set (reg:DI 93)
(const_int -9223372036854775808 [0x8000000000000000])) t.c:5 89
{*movdi_internal}
(nil))
(insn 9 8 10 2 (parallel [
(set (reg:DI 92 [ x ])
(and:DI (reg:DI 91 [ D.1848 ])
(reg:DI 93)))
(clobber (reg:CC 17 flags))
]) t.c:5 381 {*anddi_1}
(expr_list:REG_DEAD (reg:DI 93)
(expr_list:REG_DEAD (reg:DI 91 [ D.1848 ])
(expr_list:REG_UNUSED (reg:CC 17 flags)
(expr_list:REG_EQUAL (and:DI (reg:DI 91 [ D.1848 ])
(const_int -9223372036854775808 [0x8000000000000000]))
(nil))))))
(insn 10 9 11 2 (set (reg:CCNO 17 flags)
(compare:CCNO (reg:DI 92 [ x ])
(const_int 0 [0]))) t.c:5 4 {*cmpdi_ccno_1}
(expr_list:REG_DEAD (reg:DI 92 [ x ])
(nil)))
After:
(note 7 6 8 2 NOTE_INSN_DELETED)
(note 8 7 9 2 NOTE_INSN_DELETED)
(note 9 8 10 2 NOTE_INSN_DELETED)
(insn 10 9 11 2 (set (reg:CCZ 17 flags)
(compare:CCZ (zero_extract:DI (subreg:DI (reg:SI 87 [ D.1847 ]) 0)
(const_int 1 [0x1])
(const_int 31 [0x1f]))
(const_int 0 [0]))) t.c:5 368 {*testqi_ext_3}
(expr_list:REG_DEAD (reg:SI 87 [ D.1847 ])
(nil)))
The zero-extract is weird and the subreg should be the high-part?
