Fold {2, 3, 4, 5} >> 31

Jakub Jelinek jakub@redhat.com
Thu Apr 11 19:58:00 GMT 2013


On Thu, Apr 11, 2013 at 06:24:02PM +0200, Marc Glisse wrote:
> here is a patch to handle constant folding of mixed vector-integer
> operations. I could have shared the loop with the vector-vector
> case, but that would have meant re-testing if arg2 was a vector at
> every iteration (I can go back to that version if you prefer).

Yeah, that is the kind of thinking I had too.

> +  /* Shifts allow a scalar offset for a vector.  */
> +  if (TREE_CODE (arg1) == VECTOR_CST)

I'd prefer && TREE_CODE (arg2) == INTEGER_CST added to the condition
here.

> +    {
> +      tree type = TREE_TYPE (arg1);
> +      int count = TYPE_VECTOR_SUBPARTS (type), i;
> +      tree *elts =  XALLOCAVEC (tree, count);

Please use just one space.

> +
> +      for (i = 0; i < count; i++)
> +	{
> +          tree elem1 = VECTOR_CST_ELT (arg1, i);
> +
> +          elts[i] = const_binop (code, elem1, arg2);
> +
> +          /* It is possible that const_binop cannot handle the given
> +            code and return NULL_TREE */
> +	  if (elts[i] == NULL_TREE)
>              return NULL_TREE;

And please use tabs where possible, instead of 8 spaces.

> --- gcc/testsuite/gcc.dg/fold-cstvecshift.c	(revision 0)
> +++ gcc/testsuite/gcc.dg/fold-cstvecshift.c	(revision 0)
> @@ -0,0 +1,13 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O -fdump-tree-ccp1" } */
> +
> +typedef int vec __attribute__ ((vector_size (4 * sizeof (int))));
> +
> +void f (vec *r)
> +{
> +  vec a = { 2, 3, 4, 5 };
> +  *r = (a << 2) >> 1;
> +}
> +
> +/* { dg-final { scan-tree-dump "{ 4, 6, 8, 10 }" "ccp1"} } */
> +/* { dg-final { cleanup-tree-dump "ccp1" } } */

Have you tested the testcase say for -m32 -mno-sse too, to see
if it doesn't fail without HW vector support?
If so, the patch is ok with the above mentioned changes.

	Jakub



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