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Subject: [Bug tree-optimization/18557] Inefficient code generated by -ftree-vectorize on Alpha
Date: Fri, 13 Jul 2012 13:53:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18557

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |DUPLICATE

--- Comment #13 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-07-13 13:52:25 UTC ---
At -O3 we now get calls to memset for the original testcase, changing it to
store 1 instead we get

$f..ng:
f:
        .frame $30,0,$26,0
        .prologue 0
        and $16,4,$1
        cmpult $31,$1,$1
        lda $7,64($31)
        addl $31,$1,$2
        mov $31,$22
        beq $2,$L2
        lda $7,63($31)
        lda $22,1($31)
        lda $3,1($31)
        stl $3,0($16)
$L2:
        lda $3,64($31)
        subl $3,$2,$2
        zapnot $2,15,$8
        lda $5,1($31)
        srl $8,1,$6
        sll $5,32,$5
        addl $6,$6,$2
        s4addq $1,$16,$1
        mov $31,$3
        zapnot $6,15,$6
        lda $5,1($5)
        .align 4
$L6:
        addl $3,1,$3
        stq $5,0($1)
        zapnot $3,15,$4
        lda $1,8($1)
        cmpult $4,$6,$4
        bne $4,$L6
        zapnot $2,15,$3
        addl $22,$2,$1
        cmpeq $8,$3,$8
        cpys $f31,$f31,$f31
        subl $7,$2,$2
        bne $8,$L8
        s4addq $1,0,$1
        lda $4,1($31)
        .align 4
$L5:
        addq $16,$1,$3
        subl $2,1,$2
        stl $4,0($3)
        lda $1,4($1)
        bne $2,$L5
$L8:
        ret $31,($26),1
        .end f

which seems to be reasonable.  We still run into the issue that we do
not recognize that the epilogue loop may at most iterate once.  The
vectorizer makes a mess out of induction variables for the prologue/epilogue
loops.  See PR53355 for where I track this general issue.

*** This bug has been marked as a duplicate of bug 53355 ***