[Bug target/40243] New: no aligned instruction generated for i386

2009-05-25 Thread abhishek dot shrivastav24 at gmail dot com 
Even a simple program like:

for(i=0;i1000;i++)
a[i]= b[i]+c[i];

is vectorized using -ftree-vectorize -msse2 -O2 flag. Unaligned instruction are
generated. For any program, Not even a single aligned instruction is generated.

As, the variable STACK_BOUNDARY in function vect_can_force_dr_alignment_p in
file tree-vectorizer.c:1798 is defined to be BITS_PER_WORD(32) for i386 in
i386.h . while this should be 128, so this variable should be replaced by some
other variable or might be again restored to PREFERRED_STACK_BOUNDARY, like
previous versions.

In version 4.4.0 , it is replaced by MAX_STACK_ALIGNMENT, which is defined as
MAX_OFILE_ALIGNEMENT in i386.h. So, both conditions return ,the same answer (
alignment = MAX_OFILE_ALIGNMENT).


-- 
   Summary: no aligned instruction generated for i386
   Product: gcc
   Version: 4.3.3
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: target
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: abhishek dot shrivastav24 at gmail dot com
 GCC build triplet: i686-unknown-linux
  GCC host triplet: i686-unknown-linux
GCC target triplet: i686-unknown-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40243

[Bug target/40243] no aligned instruction generated for i386

2009-05-25 Thread abhishek dot shrivastav24 at gmail dot com 


--- Comment #2 from abhishek dot shrivastav24 at gmail dot com  2009-05-25 
14:36 ---
(In reply to comment #1)
 Works for me (your simple program is not a valid program).
 

The whole program is like this:

/* sample.c */
#include stdio.h
#define N 1000
int main()
{
   int a[N], b[N], c[N], i;
   for(i=0;iN;i++)
   b[i]=c[i]=i;

 for(i=0;iN;i++)
 a[i]=b[i]+c[i];

   for(i=0;iN;i++)
printf(%d, a[i]);
}

compile using gcc version 4.3.*, using
gcc -S -ftree-vectorize -ftree-vectorizer-verbose=10 -msse2 -O2 sample.c

Now, view the assembly file generated and also the verbose, it always prints
when analyzing in function vect_analyze_data_refs_alignment ***can't force
alignment of ref: b[i_43]***, while it does not need alignment, as it is
already aligned.

Simply changed the instruction movdqu to movdqa and no segmentation fault would
occur, as the array references are aligned.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40243