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optimization/10679: [3.3/3.4] --param min-inline-insns not honoured
- From: rguenth at tat dot physik dot uni-tuebingen dot de
- To: gcc-gnats at gcc dot gnu dot org
- Date: 8 May 2003 12:11:57 -0000
- Subject: optimization/10679: [3.3/3.4] --param min-inline-insns not honoured
- Reply-to: rguenth at tat dot physik dot uni-tuebingen dot de
>Number: 10679
>Category: optimization
>Synopsis: [3.3/3.4] --param min-inline-insns not honoured
>Confidential: no
>Severity: critical
>Priority: medium
>Responsible: unassigned
>State: open
>Class: pessimizes-code
>Submitter-Id: net
>Arrival-Date: Thu May 08 12:16:00 UTC 2003
>Closed-Date:
>Last-Modified:
>Originator: Richard Guenther
>Release: g++-3.3 (GCC) 3.3 20030505 (prerelease), g++-3.4 (GCC) 3.4 20030505 (experimental)
>Organization:
>Environment:
ia32 gnu-linux
>Description:
If specifying --param min-inline-insns one expects from the manual all functions with size <= min-inline-insns to be inlined. This is not the case if inlining repeatedly into a large function as can be seen from comments/code in tree-inline.c:inlinable_function_p (line 1003-)
This severly pessimizes scientific code based on the POOMA library, where inlining of small function is vitally important. After applying the attached patch, >30% performance can be gained and the --param min-inline-insns behaves as documented.
No testcase, the defect can be pinpointed in the gcc source. A testcase would look like
inline void bar(void) { }
void foo(void)
{
bar(); bar(); bar(); /* repeat 10000 times... */
}
at a certain point, bar()s would be no longer inlined and
the resulting foo() would not be empty.
>How-To-Repeat:
Repeatedly inline a small function into a large one.
>Fix:
Apply the attached patch.
>Release-Note:
>Audit-Trail:
>Unformatted:
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