https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67396
Bug ID: 67396
Summary: [4.9/5.0 regression] Performance regression compiling
variadic function with many arguments
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: ppluzhnikov at google dot com
Target Milestone: ---
Created attachment 36270
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36270&action=edit
test generator script
For https://sourceware.org/bugzilla/show_bug.cgi?id=18872, I need a test case
that calls printf() with >= 2700 arguments.
GCC-4.9 and 5.0 (and current trunk) take excessively long to compile such test
cases with optimization:
$ perl gen_bz18872.pl 500 > t.c && time gcc-svn-r227321/bin/gcc -c -O2 t.c
user 0m1.506s
$ perl gen_bz18872.pl 1000 > t.c && time gcc-svn-r227321/bin/gcc -c -O2 t.c
user 0m11.976s
$ perl gen_bz18872.pl 2000 > t.c && gcc-svn-r227321/bin/gcc -c -O2 t.c
user 1m40.911s
$ perl gen_bz18872.pl 4000 > t.c && gcc-svn-r227321/bin/gcc -c -O2 t.c
user 14m0.767s ### Yikes!
For comparison, gcc-4.8 (Ubuntu 4.8.4-2ubuntu1~14.04) 4.8.4 compiles the 4000
argument case in 1.3s.
The problem is already present in r220312 (the oldest build I have).
