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* [Bug c/14816] New: -fno-crossjumping not working for large code?
@ 2004-04-02 0:25 mj_ at gazeta dot pl
2004-04-02 0:36 ` [Bug c/14816] " pinskia at gcc dot gnu dot org
0 siblings, 1 reply; 2+ messages in thread
From: mj_ at gazeta dot pl @ 2004-04-02 0:25 UTC (permalink / raw)
To: gcc-bugs
I'm not sure if it really belongs here, but I hope it won't hurt..
I am working on kind-of interpreter, which consists of series of indirect branches:
label1:
...
goto *ip;
...
labelN:
...
goto *ip;
After optimization it is translated to more-or-less assembly equivalent of:
label0:
goto *ip;
label1:
...
goto label0;
...
labelN:
...
goto label0;
That layout is hurting branch prediction, so I tried to disable it with
-fno-crossjumping, which I believe is responsible for this optimization.
For small code [tens of cases] it worked, but for larger one [hundreds] the
compiler still performed that optimization.
For comparison I ran GCC 3.3 with:
--param max-crossjump-edges=400 -fno-crossjumping
and it worked as expected.
[with default values it didn't link indirect branches in the larger case anyway]
--
Summary: -fno-crossjumping not working for large code?
Product: gcc
Version: 3.4.0
Status: UNCONFIRMED
Severity: minor
Priority: P2
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: mj_ at gazeta dot pl
CC: gcc-bugs at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14816
^ permalink raw reply [flat|nested] 2+ messages in thread
* [Bug c/14816] -fno-crossjumping not working for large code?
2004-04-02 0:25 [Bug c/14816] New: -fno-crossjumping not working for large code? mj_ at gazeta dot pl
@ 2004-04-02 0:36 ` pinskia at gcc dot gnu dot org
0 siblings, 0 replies; 2+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2004-04-02 0:36 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2004-04-02 00:36 -------
Not a bug, see PR8092.
*** This bug has been marked as a duplicate of 8092 ***
--
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution| |DUPLICATE
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14816
^ permalink raw reply [flat|nested] 2+ messages in thread
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2004-04-02 0:25 [Bug c/14816] New: -fno-crossjumping not working for large code? mj_ at gazeta dot pl
2004-04-02 0:36 ` [Bug c/14816] " pinskia at gcc dot gnu dot org
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