[Bug c/45176] New: restrict qualifier is not used in a manually unrolled loop

[Bug c/45176] New: restrict qualifier is not used in a manually unrolled loop

[bmei at broadcom dot com]

void foo (int * restrict a, int * restrict b, int * restrict c)
{
   int i;
   for(i = 0; i < 100; i+=4)
     {
       a[i] = b[i] * c[i];
       a[i+1] = b[i+1] * c[i+1];
       a[i+2] = b[i+2] * c[i+2];
       a[i+3] = b[i+3] * c[i+3];
     }
}   

Trunk x86-64 compiler (162821) produces code that later load instructions are
not scheduled before the previous store instructions as expected. Clearly,
restrict qualifier is not used here. 

 ~/work/install-x86/bin/gcc tst3.c -O2 -S -std=c99 -da -fschedule-insns
-frename-registers
.L2:
        movl    (%rdx,%rax), %r10d
        imull   (%rsi,%rax), %r10d
        movl    %r10d, (%rdi,%rax)
        movl    4(%rdx,%rax), %r9d
        imull   4(%rsi,%rax), %r9d
        movl    %r9d, 4(%rdi,%rax)
        movl    8(%rdx,%rax), %r8d
        imull   8(%rsi,%rax), %r8d
        movl    %r8d, 8(%rdi,%rax)
        movl    12(%rdx,%rax), %ecx
        imull   12(%rsi,%rax), %ecx
        movl    %ecx, 12(%rdi,%rax)
        addq    $16, %rax
        cmpq    $400, %rax

Richard has a patch and it seems to work for this example. 
Index: expr.c
===================================================================
--- expr.c      (revision 162841)
+++ expr.c      (working copy)
@@ -8665,7 +8665,7 @@ expand_expr_real_1 (tree exp, rtx target
        set_mem_addr_space (temp, as);
        base = get_base_address (TMR_ORIGINAL (exp));
        if (base
-           && INDIRECT_REF_P (base)
+           && (INDIRECT_REF_P (base) || TREE_CODE (base) == MEM_REF)
            && TMR_BASE (exp)
            && TREE_CODE (TMR_BASE (exp)) == SSA_NAME
            && POINTER_TYPE_P (TREE_TYPE (TMR_BASE (exp))))

The code generated:
.L2:
        movl    (%rdx,%rax), %r10d
        movl    4(%rdx,%rax), %r9d
        imull   (%rsi,%rax), %r10d
        imull   4(%rsi,%rax), %r9d
        movl    8(%rdx,%rax), %r8d
        movl    12(%rdx,%rax), %ecx
        imull   8(%rsi,%rax), %r8d
        imull   12(%rsi,%rax), %ecx
        movl    %r10d, (%rdi,%rax)
        movl    %r9d, 4(%rdi,%rax)
        movl    %r8d, 8(%rdi,%rax)
        movl    %ecx, 12(%rdi,%rax)
        addq    $16, %rax
        cmpq    $400, %rax
        jne     .L2


-- 
           Summary: restrict qualifier is not used in a manually unrolled
                    loop
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: bmei at broadcom dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45176

[Bug c/45176] restrict qualifier is not used in a manually unrolled loop

[rguenth at gcc dot gnu dot org]

------- Comment #1 from rguenth at gcc dot gnu dot org  2010-08-04 09:19 -------
I'll bootstrap & test that patch.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |rguenth at gcc dot gnu dot
                   |dot org                     |org
             Status|UNCONFIRMED                 |ASSIGNED
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2010-08-04 09:19:37
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45176

[Bug c/45176] restrict qualifier is not used in a manually unrolled loop

[rguenth at gcc dot gnu dot org]

------- Comment #2 from rguenth at gcc dot gnu dot org  2010-08-04 11:09 -------
Subject: Bug 45176

Author: rguenth
Date: Wed Aug  4 11:08:54 2010
New Revision: 162862

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=162862
Log:
2010-08-04  Richard Guenther  <rguenther@suse.de>

        PR middle-end/45176
        * expr.c (expand_expr_real_1): Also preserve TARGET_MEM_REF
        points-to set for original MEM_REF.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/expr.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45176

[Bug c/45176] restrict qualifier is not used in a manually unrolled loop

[rguenth at gcc dot gnu dot org]

------- Comment #3 from rguenth at gcc dot gnu dot org  2010-08-04 11:09 -------
Fixed.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.6.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45176

[Bug c/45176] restrict qualifier is not used in a manually unrolled loop

[siarhei dot siamashka at gmail dot com]

------- Comment #4 from siarhei dot siamashka at gmail dot com  2010-08-05 13:40 -------
Looks like this missed optimization regression was introduced in gcc 4.5

Are any similar fixes possible in 4.5 branch?


-- 

siarhei dot siamashka at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |siarhei dot siamashka at
                   |                            |gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45176

[Bug c/45176] restrict qualifier is not used in a manually unrolled loop

[bmei at broadcom dot com]

------- Comment #5 from bmei at broadcom dot com  2010-08-05 13:44 -------
I tried to apply the patches (this one alone is not enough) Richard suggested.
It becomes a chain of too many patches in the end. I am confident any more to
apply them to 4.5. 


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45176