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* Re: c/1687: [3.3/3.4 regression] Extreme compile time regression from 2.95.3
@ 2003-04-17 13:16 Steven Bosscher
0 siblings, 0 replies; only message in thread
From: Steven Bosscher @ 2003-04-17 13:16 UTC (permalink / raw)
To: nobody; +Cc: gcc-prs
The following reply was made to PR c/1687; it has been noted by GNATS.
From: Steven Bosscher <s.bosscher@student.tudelft.nl>
To: gcc-gnats@gcc.gnu.org, kelley.cook@home.com,
gcc-bugs@gcc.gnu.org, nobody@gcc.gnu.org, gcc-prs@gcc.gnu.org,
mark@codesourcery.com
Cc:
Subject: Re: c/1687: [3.3/3.4 regression] Extreme compile time regression
from 2.95.3
Date: Thu, 17 Apr 2003 15:11:21 +0200
Hi,
The GCC C front end shows exponential behavior in time for this
code with -finline-functions. The time is spent in walk_tree but
the problem may be elsewhere, I haven't looked at that yet.
--------------------------------
typedef int bool;
bool in0, in1, in2, in3, in4, in5, in6, in7, in8, in9;
unsigned long output;
void mux(void)
{
output =
(in0 ? 0x00000001 : 0) | (in1 ? 0x00000008 : 0) |
(in2 ? 0x00000001 : 0) | (in3 ? 0x00000008 : 0) |
(in4 ? 0x00000001 : 0) | (in5 ? 0x00000008 : 0) |
(in6 ? 0x00000001 : 0) | (in7 ? 0x00000008 : 0) |
(in8 ? 0x00000001 : 0) | (in9 ? 0x00000008 : 0)
;
}
--------------------------------
This function has 10 variables "int ii??". I have similair programs
with 11, 12, 13, 14 and 15 "int ii??" variables (I started with 32,
like the original test case, but it ate memory until it died).
Here is the output for "time cc1 -quiet -O -finline-functions":
# of in?? log(user+sys) user+sys user sys
10 -0.284 0.52 0.49 0.03
11 0.130 1.35 1.35 0
12 0.590 3.89 3.87 0.02
13 1.059 11.47 11.47 0
14 1.534 34.23 34.21 0.02
15 2.012 102.92 102.88 0.04
GNU C version 3.4 20030417 (experimental) (i586-pc-linux-gnu)
compiled by GNU C version 2.95.3 20010315 (SuSE).
GGC heuristics: --param ggc-min-expand=42 --param ggc-min-heapsize=23891
The C++ front end does not show this behavior.
Greetz
Steven
http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=1687
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