This is the mail archive of the
gcc-bugs@gcc.gnu.org
mailing list for the GCC project.
Re: c/1687: [3.3/3.4 regression] Extreme compile time regressionfrom 2.95.3
- From: Steven Bosscher <s dot bosscher at student dot tudelft dot nl>
- To: gcc-gnats at gcc dot gnu dot org, kelley dot cook at home dot com,gcc-bugs at gcc dot gnu dot org, nobody at gcc dot gnu dot org, gcc-prs at gcc dot gnu dot org,mark at codesourcery dot com
- Date: Thu, 17 Apr 2003 15:11:21 +0200
- Subject: Re: c/1687: [3.3/3.4 regression] Extreme compile time regressionfrom 2.95.3
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