[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Bug optimization/14504] Missed Bit Twiddling Optimization
From: |
kazu at cs dot umass dot edu |
Subject: |
[Bug optimization/14504] Missed Bit Twiddling Optimization |
Date: |
11 Mar 2004 00:09:29 -0000 |
------- Additional Comments From kazu at cs dot umass dot edu 2004-03-11 00:09
-------
I've got a patch.
/* There are four cases to handle modulo whether FLAG appears
positively and ordering of operands TARGET and MASK in the
expression.
With my patch, gcc -O2 -fomit-frame-pointer -mregparm=3 generates
the following assembly code. */
typedef _Bool bool;
unsigned long
cond_mask_0 (bool flag, unsigned long mask, unsigned long target)
{
return flag ? target | mask : target & ~mask;
#if 0
movzbl %al, %eax
decl %eax
xorl %eax, %ecx
orl %edx, %ecx
xorl %ecx, %eax
#endif
}
unsigned long
cond_mask_1 (bool flag, unsigned long mask, unsigned long target)
{
return flag ? target | ~mask : target & mask;
#if 0
movzbl %al, %eax
negl %eax
xorl %eax, %ecx
andl %edx, %ecx
xorl %ecx, %eax
#endif
}
unsigned long
cond_mask_2 (bool flag, unsigned long mask, unsigned long target)
{
return flag ? target & mask : target | ~mask;
#if 0
movzbl %al, %eax
decl %eax
xorl %eax, %ecx
andl %edx, %ecx
xorl %ecx, %eax
#endif
}
unsigned long
cond_mask_3 (bool flag, unsigned long mask, unsigned long target)
{
return flag ? target & ~mask : target | mask;
#if 0
movzbl %al, %eax
negl %eax
xorl %eax, %ecx
orl %edx, %ecx
xorl %ecx, %eax
#endif
}
--
What |Removed |Added
----------------------------------------------------------------------------
CC| |kazu at cs dot umass dot edu
AssignedTo|unassigned at gcc dot gnu |kazu at cs dot umass dot edu
|dot org |
Status|NEW |ASSIGNED
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14504
- [Bug optimization/14504] Missed Bit Twiddling Optimization, stl at caltech dot edu, 2004/03/12
- [Bug optimization/14504] Missed Bit Twiddling Optimization, stl at caltech dot edu, 2004/03/12
- [Bug optimization/14504] Missed Bit Twiddling Optimization, kazu at cs dot umass dot edu, 2004/03/13
- [Bug optimization/14504] Missed Bit Twiddling Optimization, stl at caltech dot edu, 2004/03/13
- [Bug optimization/14504] Missed Bit Twiddling Optimization, falk at debian dot org, 2004/03/13
- [Bug optimization/14504] Missed Bit Twiddling Optimization, kazu at cs dot umass dot edu, 2004/03/13
- [Bug optimization/14504] Missed Bit Twiddling Optimization,
kazu at cs dot umass dot edu <=