[PATCH] fix PR middle-end/22480

[Uros Bizjak <ubizjak at gmail dot com>]

Hello!

  This patch fixes the problem with vector shifts, where shift value
is defined as a scalar value. This upsets vectoriser, which expects
that vectors are shifted by a vector of values.

  The proposed solution is, that vectorizer looks into insn pattern
that corresponds to vectorizer optab, and checks the mode of operand 2
(shift value in case of vectoriser shifts). If the mode of operand 2
is scalar mode, then simply use a scalar or loop invariant shift value
as paramtere to the vector operation optab.

  The testcase:

void
test_1 (void)
{
  static unsigned int bm[16];
  int j;
  for (j = 0; j < 16; j++)
    bm[j] <<= 8;
}

void
test_2 (int a)
{
  static unsigned int bm[16];
  int j;
  for (j = 0; j < 16; j++)
    bm[j] <<= a;
}

then compiles to:

(vector shift by constant)
test_1:
pushl %ebp
movl $bm.1591, %eax
movl %esp, %ebp
movl $bm.1591, %edx
.p2align 4,,15
.L2:
movdqa (%eax), %xmm0
addl $4, %edx
pslld $8, %xmm0
movdqa %xmm0, (%eax)
addl $16, %eax
cmpl $bm.1591+16, %edx
jne .L2
popl %ebp
ret

and

(vector shift by parameter)
test_2:
pushl %ebp
movl $bm.1602, %eax
movl %esp, %ebp
movl $bm.1602, %edx
movd 8(%ebp), %xmm1
.p2align 4,,15
.L9:
movdqa (%eax), %xmm0
addl $4, %edx
pslld %xmm1, %xmm0
movdqa %xmm0, (%eax)
addl $16, %eax
cmpl $bm.1602+16, %edx
jne .L9
popl %ebp
ret

2005-09-07  Uros Bizjak  <uros@kss-loka.si>

PR middle-end/22480
* tree-vect-transform.c (vectorizable_operation): Fallback to
scalar mode for tree operand 1, if operand 2 of vector insn pattern
can not handle vector modes.
* Makefile.in (tree-vect-transform.o): Depend on recog.h.


testsuite/ChangeLog:

2005-09-07  Uros Bizjak  <uros@kss-loka.si>

PR middle-end/22480
* gcc.dg/vect/pr22480.c: New test.

Patch was regtested for c anc c++ on i686-pc-linux-gnu.

Uros.

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