http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58517
Bug ID: 58517
Summary: [SH] wrong code with subc and movsicc
(-mpretend-cmove) after ce2
Product: gcc
Version: 4.9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: olegendo at gcc dot gnu.org
Target: sh*-*-*
While working on something else, I've noticed the following sequence in the
CSiBE set in the file zlib-1.1.4/infblock.s, compiling with -m4-single -ml -O2
-mpretend-cmove (trunk rev 201978):
.L257:
sett ! 1740 sett [length = 2]
mov r2,r13 ! 2180 movsi_ie/2 [length = 2]
sub r5,r1 ! 1588 *subsi3_internal [length = 2]
subc r5,r13 ! 1741 *subc [length = 2]
bt 0f ! 1589 *movsicc_t_false/1 [length = 4]
mov r1,r13
0:
tst r13,r13 ! 435 cmpeqsi_t/1 [length = 2]
bf .L67 ! 436 *cbranch_t [length = 2]
bra .L124
nop ! 2774 jump_compact [length = 4]
The subc insn clobbers the T_REG and the following 'bt 0f' just looks wrong.
It seems that something goes wrong and the insn that does the test before
*movsicc_t_false gets eliminated because the sett-subc sequence is placed in
between.
After the combine pass the sequence looks like:
(note 422 421 423 45 [bb 45] NOTE_INSN_BASIC_BLOCK)
(insn 423 422 432 45 (set (reg:SI 147 t)
(gtu:SI (reg/f:SI 424 [ D.2926 ])
(reg/v/f:SI 189 [ q ]))) infblock.c:202 34 {cmpgtusi_t}
(nil))
(insn 432 423 424 45 (set (reg/v:SI 190 [ n ])
(minus:SI (reg/v/f:SI 423 [ q ])
(reg/v/f:SI 189 [ q ]))) infblock.c:202 76 {*subsi3_internal}
(expr_list:REG_DEAD (reg/v/f:SI 423 [ q ])
(nil)))
(jump_insn 424 432 425 45 (set (pc)
(if_then_else (eq (reg:SI 147 t)
(const_int 0 [0]))
(label_ref:SI 433)
(pc))) infblock.c:202 295 {*cbranch_t}
(expr_list:REG_DEAD (reg:SI 147 t)
(expr_list:REG_BR_PROB (const_int 5000 [0x1388])
(nil)))
-> 433)
(note 425 424 426 46 [bb 46] NOTE_INSN_BASIC_BLOCK)
(note 426 425 427 46 NOTE_INSN_DELETED)
(insn 427 426 433 46 (parallel [
(set (reg/v:SI 190 [ n ])
(plus:SI (not:SI (reg/v/f:SI 189 [ q ]))
(reg/f:SI 424 [ D.2926 ])))
(clobber (reg:SI 147 t))
]) infblock.c:202 74 {*subc}
(expr_list:REG_UNUSED (reg:SI 147 t)
(expr_list:REG_DEAD (reg/f:SI 424 [ D.2926 ])
(nil))))
(code_label 433 427 434 47 70 "" [1 uses])
After the following pass ce2 it becomes:
(note 422 421 423 45 [bb 45] NOTE_INSN_BASIC_BLOCK)
(insn 423 422 432 45 (set (reg:SI 147 t)
(gtu:SI (reg/f:SI 424 [ D.2926 ])
(reg/v/f:SI 189 [ q ]))) infblock.c:202 34 {cmpgtusi_t}
(nil))
(insn 432 423 1587 45 (set (reg/v:SI 190 [ n ])
(minus:SI (reg/v/f:SI 423 [ q ])
(reg/v/f:SI 189 [ q ]))) infblock.c:202 76 {*subsi3_internal}
(expr_list:REG_DEAD (reg/v/f:SI 423 [ q ])
(nil)))
(insn 1587 432 1588 45 (parallel [
(set (reg:SI 945)
(plus:SI (not:SI (reg/v/f:SI 189 [ q ]))
(reg/f:SI 424 [ D.2926 ])))
(clobber (reg:SI 147 t))
]) infblock.c:202 74 {*subc}
(nil))
(insn 1588 1587 1589 45 (set (reg:SI 946)
(minus:SI (reg/v/f:SI 423 [ q ])
(reg/v/f:SI 189 [ q ]))) infblock.c:202 76 {*subsi3_internal}
(nil))
(insn 1589 1588 435 45 (set (reg/v:SI 190 [ n ])
(if_then_else:SI (eq (reg:SI 147 t)
(const_int 0 [0]))
(reg:SI 946)
(reg:SI 945))) infblock.c:202 54 {*movsicc_t_false}
(nil))
(insn 435 1589 436 45 (set (reg:SI 147 t)
(eq:SI (reg/v:SI 190 [ n ])
(const_int 0 [0]))) infblock.c:202 17 {cmpeqsi_t}
(nil))
(jump_insn 436 435 1378 45 (set (pc)
(if_then_else (eq (reg:SI 147 t)
(const_int 0 [0]))
(label_ref 501)
(pc))) infblock.c:202 295 {*cbranch_t}
(expr_list:REG_DEAD (reg:SI 147 t)
(expr_list:REG_BR_PROB (const_int 10000 [0x2710])
(nil)))
-> 501)
which is wrong. I haven't checked whether it also happens on current trunk.
