https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89049
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |segher at gcc dot gnu.org
--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
So combine can see
(insn 11 10 13 3 (set (reg:V8SF 105)
(vec_concat:V8SF (reg:V4SF 106 [ MEM[base: _2, offset: 0B] ])
(mem:V4SF (plus:DI (reg:DI 85 [ ivtmp.11 ])
(const_int 16 [0x10])) [1 MEM[base: _2, offset: 0B]+16 S16
A32]))) "t.c":1:72 5046 {avx_vec_concatv8sf}
(nil))
with its uses
(insn 13 11 14 3 (set (reg:V4SF 107)
(vec_select:V4SF (reg:V8SF 105)
(parallel [
(const_int 0 [0])
(const_int 1 [0x1])
(const_int 2 [0x2])
(const_int 3 [0x3])
]))) 2702 {vec_extract_lo_v8sf}
(nil))
(insn 25 24 26 3 (set (reg:V4SF 111)
(vec_select:V4SF (reg:V8SF 105)
(parallel [
(const_int 4 [0x4])
(const_int 5 [0x5])
(const_int 6 [0x6])
(const_int 7 [0x7])
]))) 2711 {vec_extract_hi_v8sf}
(expr_list:REG_DEAD (reg:V8SF 105)
(nil)))
but somehow it only tries 11 -> 13:
Trying 11 -> 13:
11: r105:V8SF=vec_concat(r106:V4SF,[r85:DI+0x10])
REG_DEAD r106:V4SF
13: r107:V4SF=vec_select(r105:V8SF,parallel)
...
Successfully matched this instruction:
(set (reg:V8SF 105)
(vec_concat:V8SF (reg:V4SF 106 [ MEM[base: _2, offset: 0B] ])
(mem:V4SF (plus:DI (reg:DI 85 [ ivtmp.11 ])
(const_int 16 [0x10])) [1 MEM[base: _2, offset: 0B]+16 S16
A32])))
Successfully matched this instruction:
(set (reg:V4SF 107)
(reg:V4SF 106 [ MEM[base: _2, offset: 0B] ]))
allowing combination of insns 11 and 13
original costs 4 + 4 = 8
replacement costs 4 + 4 = 8
modifying insn i2 11: r105:V8SF=vec_concat(r106:V4SF,[r85:DI+0x10])
deferring rescan insn with uid = 11.
modifying insn i3 13: r107:V4SF=r106:V4SF
REG_DEAD r106:V4SF
then it continues:
Trying 11 -> 25:
11: r105:V8SF=vec_concat(r106:V4SF,[r85:DI+0x10])
25: r111:V4SF=vec_select(r105:V8SF,parallel)
REG_DEAD r105:V8SF
Successfully matched this instruction:
(set (reg:V4SF 111)
(mem:V4SF (plus:DI (reg:DI 85 [ ivtmp.11 ])
(const_int 16 [0x10])) [1 MEM[base: _2, offset: 0B]+16 S16 A32]))
rejecting combination of insns 11 and 25
original costs 4 + 4 = 8
replacement cost 12
where it rejects this for some reason... I think the cost of 4
assigned to 11 is bogus here (maybe combine uses wrong costs, not
accounting for embedded MEMs?)
