[Bug middle-end/23477] [4.1 Regression] default-initializing array new expression uses makes stack usage go way up

[pinskia at gcc dot gnu dot org]

--- Comment #7 from pinskia at gcc dot gnu dot org  2006-01-20 20:51 ---
*** Bug 23631 has been marked as a duplicate of this bug. ***


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23477

[Bug middle-end/23477] [4.1 Regression] default-initializing array new expression uses makes stack usage go way up

[cvs-commit at gcc dot gnu dot org]

--- Additional Comments From cvs-commit at gcc dot gnu dot org  2005-08-31 
11:21 ---
Subject: Bug 23477

CVSROOT:/cvs/gcc
Module name:gcc
Changes by: [EMAIL PROTECTED]   2005-08-31 11:20:48

Modified files:
gcc: ChangeLog expr.c 

Log message:
2005-08-31  Richard Guenther  [EMAIL PROTECTED]

PR middle-end/23477
* expr.c (all_zeros_p): New function.
(expand_expr_real_1): Handle the case of an all-zero
non-addressable constructor separately.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gccr1=2.9855r2=2.9856
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/expr.c.diff?cvsroot=gccr1=1.811r2=1.812



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23477

[Bug middle-end/23477] [4.1 Regression] default-initializing array new expression uses makes stack usage go way up

[rguenth at gcc dot gnu dot org]

--- Additional Comments From rguenth at gcc dot gnu dot org  2005-08-31 
11:21 ---
Fixed.

-- 
   What|Removed |Added

 Status|ASSIGNED|RESOLVED
 Resolution||FIXED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23477

[Bug middle-end/23477] [4.1 Regression] default-initializing array new expression uses makes stack usage go way up

[pinskia at gcc dot gnu dot org]

--- Additional Comments From pinskia at gcc dot gnu dot org  2005-08-30 
10:39 ---
*** Bug 23631 has been marked as a duplicate of this bug. ***

-- 
   What|Removed |Added

 CC||etienne_lorrain at yahoo dot
   ||fr


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23477

[Bug middle-end/23477] [4.1 Regression] default-initializing array new expression uses makes stack usage go way up

[rguenth at gcc dot gnu dot org]

--- Additional Comments From rguenth at gcc dot gnu dot org  2005-08-30 
13:16 ---
Patch submitted.

-- 
   What|Removed |Added

URL||http://gcc.gnu.org/ml/gcc-
   ||patches/2005-
   ||08/msg01747.html
   Keywords||patch


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23477

[Bug middle-end/23477] [4.1 Regression] default-initializing array new expression uses makes stack usage go way up

[pinskia at gcc dot gnu dot org]

--- Additional Comments From pinskia at gcc dot gnu dot org  2005-08-19 
11:28 ---
This has been semi fixed on the mainline:
main:
pushl   %ebp
movl%esp, %ebp
pushl   %esi
pushl   %ebx
subl$4000, %esp
pushl   $4000
call_Znaj
leal-4008(%ebp), %ebx
pushl   $4000
pushl   $0
pushl   %ebx
movl%eax, %esi
callmemset
pushl   $4000
pushl   %ebx
pushl   %esi
callmemcpy
leal-8(%ebp), %esp
xorl%eax, %eax
popl%ebx
popl%esi
popl%ebp
ret

But in fact this is worse as the reason for the heap allocation is to avoid  
the stack usage at all and now 
there is 40MB allocated on the stack.

The problem is in the middle-end:
  *(int[1000] *) D.1731 = {};


Note the memcpy is an improvement over what before 4.0.0 had of writting out 
element by element.

4.1's problem is a regression in terms of stack usage which should not have 
happen.

-- 
   What|Removed |Added

 Status|UNCONFIRMED |NEW
  Component|c++ |middle-end
 Ever Confirmed||1
  GCC build triplet|i386-redhat-linux   |
   GCC host triplet|i386-redhat-linux   |
 GCC target triplet|i386-redhat-linux   |
   Keywords||missed-optimization
   Last reconfirmed|-00-00 00:00:00 |2005-08-19 11:28:34
   date||
Summary|default-initializing array  |[4.1 Regression] default-
   |new expression uses memcpy()|initializing array new
   |instead of memset(), bloats |expression uses makes stack
   |executable  |usage go way up
   Target Milestone|--- |4.1.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23477