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[Bug c/59802] New: excessive compile time in loop unswitching
- From: "dcb314 at hotmail dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Tue, 14 Jan 2014 08:49:40 +0000
- Subject: [Bug c/59802] New: excessive compile time in loop unswitching
- Auto-submitted: auto-generated
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59802
Bug ID: 59802
Summary: excessive compile time in loop unswitching
Product: gcc
Version: 4.9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: dcb314 at hotmail dot com
Created attachment 31830
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=31830&action=edit
gzipped C++ source code
I just compiled the attached code with gcc trunk 20140112 on a x86_64
box with flag -O3 and it took over eight minutes. Using only -O2 took
a more reasonable 2 minutes 38 seconds.
For reference, the redhat version of gcc 482 took 2 minutes 32 seconds
for -O3 and 2 minutes 11 seconds for -O2.
I can see that for -O2, trunk is using about 30 seconds more CPU time,
which is fine, but for -O3 over 5 minutes more.
I tried flag -ftime-report and here are all the times > 1%.
Execution times (seconds)
phase opt and generate : 465.18 (100%) usr 0.50 (57%) sys 468.04 (100%)
wall 130935 kB (59%) ggc
loop invariant motion : 22.50 ( 5%) usr 0.01 ( 1%) sys 22.85 ( 5%) wall
2 kB ( 0%) ggc
loop unswitching : 302.37 (65%) usr 0.01 ( 1%) sys 303.82 (65%) wall
72 kB ( 0%) ggc
CPROP : 85.02 (18%) usr 0.09 (10%) sys 85.52 (18%) wall
4445 kB ( 2%) ggc
TOTAL : 466.12 0.88 469.55
221219 kB
Suggest code rework for trunk for -O3, maybe in the area of loop unswitching.
This bug may be a duplicate of bug 38518