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[parent not found: <bug-18557-2744@http.gcc.gnu.org/bugzilla/>]
* [Bug tree-optimization/18557] New: Inefficient code generated by -ftree-vectorize on Alpha
@ 2004-11-18 23:54 falk at debian dot org
  2004-11-19  0:04 ` [Bug tree-optimization/18557] " pinskia at gcc dot gnu dot org
                   ` (6 more replies)
  0 siblings, 7 replies; 13+ messages in thread
From: falk at debian dot org @ 2004-11-18 23:54 UTC (permalink / raw)
  To: gcc-bugs

For this code:

int f(unsigned int *p) {
    for (int i = 0; i < 64; ++i)
	p[i] = 0;
}

I'd expect to get something like the output for this code:

int f2(unsigned int *p) {
    int c = 64*4;
    if ((unsigned long) p % 8) *p++ = 0, c -= 4;
    unsigned long *l = p;
    do *l++ = 0; while ((c -= 8) >= 8);
    p = l;
    if (c) *p++ = 0;
}

which is

f2:
	and $16,7,$1
	lda $4,256($31)
	beq $1,$L11
	stl $31,0($16)
	lda $4,252($31)
	lda $16,4($16)
$L11:
	mov $31,$3
	.align 4
$L12:
	lda $3,8($3)
	stq $31,0($16)
	lda $16,8($16)
	subl $4,$3,$2
	cmple $2,7,$1
	beq $1,$L12
	beq $2,$L17
	stl $31,0($16)
$L17:
	ret

but I get:

f:
	and $16,4,$1
	lda $5,64($31)
	lda $6,64($31)
	mov $31,$7
	cmpult $31,$1,$1
	cmplt $1,64,$2
	cmovne $2,$1,$5
	ble $5,$L4
	mov $31,$3
	mov $31,$4
	.align 4
$L12:
	lda $3,1($3)
	s4addq $4,$16,$1
	addl $31,$3,$4
	stl $31,0($1)
	addl $31,$4,$2
	cmple $5,$2,$1
	beq $1,$L12
	lda $1,64($31)
	mov $2,$7
	subl $1,$4,$6
$L4:
	cmpeq $5,64,$1
	bne $1,$L6
	lda $1,64($31)
	subq $1,$5,$22
	sra $22,1,$4
	addq $4,$4,$8
	ble $8,$L8
	s4addq $5,$16,$2
	mov $31,$3
	.align 4
$L10:
	lda $3,1($3)
	stq $31,0($2)
	lda $2,8($2)
	addl $31,$3,$1
	cmple $4,$1,$1
	beq $1,$L10
	subl $6,$8,$6
	addl $7,$8,$7
$L8:
	cmpeq $22,$8,$1
	bne $1,$L6
	mov $31,$2
	.align 4
$L14:
	addl $2,$7,$1
	subl $6,1,$6
	lda $2,1($2)
	s4addq $1,$16,$1
	stl $31,0($1)
	bne $6,$L14
$L6:
	ret

which is pretty weird and inefficent code...

-- 
           Summary: Inefficient code generated by -ftree-vectorize on Alpha
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: falk at debian dot org
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: alphaev68-unknown-linux-gnu
  GCC host triplet: alphaev68-unknown-linux-gnu
GCC target triplet: alphaev68-unknown-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18557


^ permalink raw reply	[flat|nested] 13+ messages in thread
end of thread, other threads:[~2012-07-13 13:53 UTC | newest]

Thread overview: 13+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
     [not found] <bug-18557-4@http.gcc.gnu.org/bugzilla/>
2012-07-13  8:54 ` [Bug tree-optimization/18557] Inefficient code generated by -ftree-vectorize on Alpha rguenth at gcc dot gnu.org
2012-07-13 13:53 ` rguenth at gcc dot gnu.org
     [not found] <bug-18557-2744@http.gcc.gnu.org/bugzilla/>
2009-02-03 12:24 ` ubizjak at gmail dot com
2009-02-03 12:25 ` ubizjak at gmail dot com
2009-02-03 12:31 ` ubizjak at gmail dot com
2009-02-03 12:51 ` falk at debian dot org
2004-11-18 23:54 [Bug tree-optimization/18557] New: " falk at debian dot org
2004-11-19  0:04 ` [Bug tree-optimization/18557] " pinskia at gcc dot gnu dot org
2004-11-19  3:42 ` dberlin at dberlin dot org
2004-11-19 10:50 ` giovannibajo at libero dot it
2004-11-19 11:29 ` falk at debian dot org
2004-11-19 14:21 ` pinskia at gcc dot gnu dot org
2004-11-19 18:24 ` dorit at il dot ibm dot com
2004-11-19 20:16 ` falk at debian dot org

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