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* [Bug target/54830] New: [SH] Unnecessary exts.w before extu.b
@ 2012-10-06 0:04 olegendo at gcc dot gnu.org
2012-10-18 19:24 ` [Bug target/54830] " olegendo at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: olegendo at gcc dot gnu.org @ 2012-10-06 0:04 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54830
Bug #: 54830
Summary: [SH] Unnecessary exts.w before extu.b
Classification: Unclassified
Product: gcc
Version: 4.8.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: target
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: olegendo@gcc.gnu.org
Target: sh*-*-*
While working on another issue, I've spotted the following sequence
swap.w r11,r1
exts.w r1,r1
extu.b r1,r2
mov.l @(16,r12),r1
in CSiBE/jpeg-6b/jcphuff.c, function _emit_eobrun, when compiling with
-m4-single -ml -O2 -mpretend-cmove.
I will try to investigate that later.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/54830] [SH] Unnecessary exts.w before extu.b
2012-10-06 0:04 [Bug target/54830] New: [SH] Unnecessary exts.w before extu.b olegendo at gcc dot gnu.org
@ 2012-10-18 19:24 ` olegendo at gcc dot gnu.org
2012-10-18 19:25 ` olegendo at gcc dot gnu.org
2012-11-07 21:27 ` olegendo at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: olegendo at gcc dot gnu.org @ 2012-10-18 19:24 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54830
--- Comment #1 from Oleg Endo <olegendo at gcc dot gnu.org> 2012-10-18 19:24:36 UTC ---
Created attachment 28487
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28487
Reduced test case
This is the reduced test case. It shows that there are actually two redundant
zero/sign extensions when compiling with -m4 {-ml|-mb} -O2:
swap.w r5,r5 ! 88 rotlsi3_16
...
exts.w r5,r5 ! 89 *extendhisi2_compact_reg
...
extu.b r5,r9 ! 10 *zero_extendqisi2_compact
...
extu.b r9,r12 ! 11 *zero_extendqisi2_compact
...
Turning on the REE pass (-free) doesn't seem to help this either.
Adding the following pattern to sh.md:
(define_insn_and_split "*"
[(set (match_operand:SI 0 "register_operand")
(zero_extract:SI (match_operand:SI 1 "register_operand")
(const_int 8)
(const_int 16)))]
"TARGET_SH1"
"#"
"&& 1"
[(set (match_dup 0) (lshiftrt:SI (match_dup 1) (const_int 16)))
(set (match_dup 0) (zero_extend:SI (match_dup 2)))]
{
operands[2] = gen_lowpart (QImode, operands[0]);
})
eliminates the first sign-extension (exts.w) only. The second zero-extension
can be eliminated by extending sh_try_omit_signzero_extend in sh.c accordingly.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/54830] [SH] Unnecessary exts.w before extu.b
2012-10-06 0:04 [Bug target/54830] New: [SH] Unnecessary exts.w before extu.b olegendo at gcc dot gnu.org
2012-10-18 19:24 ` [Bug target/54830] " olegendo at gcc dot gnu.org
@ 2012-10-18 19:25 ` olegendo at gcc dot gnu.org
2012-11-07 21:27 ` olegendo at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: olegendo at gcc dot gnu.org @ 2012-10-18 19:25 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54830
Oleg Endo <olegendo at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |ASSIGNED
Last reconfirmed| |2012-10-18
AssignedTo|unassigned at gcc dot |olegendo at gcc dot gnu.org
|gnu.org |
Ever Confirmed|0 |1
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/54830] [SH] Unnecessary exts.w before extu.b
2012-10-06 0:04 [Bug target/54830] New: [SH] Unnecessary exts.w before extu.b olegendo at gcc dot gnu.org
2012-10-18 19:24 ` [Bug target/54830] " olegendo at gcc dot gnu.org
2012-10-18 19:25 ` olegendo at gcc dot gnu.org
@ 2012-11-07 21:27 ` olegendo at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: olegendo at gcc dot gnu.org @ 2012-11-07 21:27 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54830
--- Comment #2 from Oleg Endo <olegendo at gcc dot gnu.org> 2012-11-07 21:27:11 UTC ---
Just for the record..
The arithmetic right shift by 16 splits into the sequence swap.w exts.w after
combine. Thus, any other following extensions don't get combined away.
^ permalink raw reply [flat|nested] 4+ messages in thread
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2012-10-06 0:04 [Bug target/54830] New: [SH] Unnecessary exts.w before extu.b olegendo at gcc dot gnu.org
2012-10-18 19:24 ` [Bug target/54830] " olegendo at gcc dot gnu.org
2012-10-18 19:25 ` olegendo at gcc dot gnu.org
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