public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
* [Bug target/21715] New: code-generation regression
@ 2005-05-23  8:25 markus at oberhumer dot com
  2005-05-23  8:33 ` [Bug target/21715] code-generation performance regression markus at oberhumer dot com
                   ` (6 more replies)
  0 siblings, 7 replies; 8+ messages in thread
From: markus at oberhumer dot com @ 2005-05-23  8:25 UTC (permalink / raw)
  To: gcc-bugs

During recent performance testing I have identified a number of small code
fragments where gcc 4.x produces worse code than gcc 3.4.3. Some of these may be
target specific, and I plan to gradually enter such small performance
regressions into the bug database unless there is a better way to report these.


$ cat test.c
long foo(long v) { return v & -v; }

$ gcc-3.4.3 -O3 -c test.c && objdump -d test.o

test.o:     file format elf64-x86-64

Disassembly of section .text:

0000000000000000 <foo>:
   0:   48 89 f8                mov    %rdi,%rax
   3:   48 f7 d8                neg    %rax
   6:   48 21 f8                and    %rdi,%rax
   9:   c3                      retq

$ gcc-4.1-20050516 -O3 -c test.c && objdump -d test.o

test.o:     file format elf64-x86-64

Disassembly of section .text:

0000000000000000 <foo>:
   0:   48 89 f8                mov    %rdi,%rax
   3:   48 f7 d8                neg    %rax
   6:   48 21 c7                and    %rax,%rdi
   9:   48 89 f8                mov    %rdi,%rax
   c:   c3                      retq

-- 
           Summary: code-generation regression
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: markus at oberhumer dot com
                CC: gcc-bugs at gcc dot gnu dot org
  GCC host triplet: x86_64-pc-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21715


^ permalink raw reply	[flat|nested] 8+ messages in thread
end of thread, other threads:[~2005-09-27 16:06 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2005-05-23  8:25 [Bug target/21715] New: code-generation regression markus at oberhumer dot com
2005-05-23  8:33 ` [Bug target/21715] code-generation performance regression markus at oberhumer dot com
2005-05-23 12:24 ` giovannibajo at libero dot it
2005-05-23 12:49 ` pinskia at gcc dot gnu dot org
2005-05-23 18:22 ` [Bug target/21715] [4.0/4.1 regression] " pinskia at gcc dot gnu dot org
2005-07-08  1:40 ` mmitchel at gcc dot gnu dot org
2005-09-16 19:04 ` pinskia at gcc dot gnu dot org
2005-09-27 16:07 ` mmitchel at gcc dot gnu dot org

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).