* argument of alloca in terms of units or not
@ 2011-09-29 18:09 Tom de Vries
2011-09-30 8:56 ` Richard Guenther
0 siblings, 1 reply; 2+ messages in thread
From: Tom de Vries @ 2011-09-29 18:09 UTC (permalink / raw)
To: Richard Guenther; +Cc: gcc-patches
Richard,
in gimplify_vla_decl, the alloca argument seems to be the size of the vla in units:
...
t = build_call_expr (t, 1, DECL_SIZE_UNIT (decl));
...
I wonder why we are going through this 8 vs. BITS_PER_UNIT conversion here:
...
elem_type = build_nonstandard_integer_type (BITS_PER_UNIT, 1);
n_elem = size * 8 / BITS_PER_UNIT;
align = MIN (size * 8, BIGGEST_ALIGNMENT);
...
The element size is BITS_PER_UNIT, so 1 unit, and size is in units.
Shouldn't this be:
...
Index: tree-ssa-ccp.c
===================================================================
--- tree-ssa-ccp.c (revision 179210)
+++ tree-ssa-ccp.c (working copy)
@@ -1722,8 +1722,8 @@ fold_builtin_alloca_for_var (gimple stmt
/* Declare array. */
elem_type = build_nonstandard_integer_type (BITS_PER_UNIT, 1);
- n_elem = size * 8 / BITS_PER_UNIT;
- align = MIN (size * 8, BIGGEST_ALIGNMENT);
+ n_elem = size;
+ align = MIN (size * BITS_PER_UNIT, BIGGEST_ALIGNMENT);
if (align < BITS_PER_UNIT)
align = BITS_PER_UNIT;
array_type = build_array_type_nelts (elem_type, n_elem);
...
Thanks,
- Tom
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: argument of alloca in terms of units or not
2011-09-29 18:09 argument of alloca in terms of units or not Tom de Vries
@ 2011-09-30 8:56 ` Richard Guenther
0 siblings, 0 replies; 2+ messages in thread
From: Richard Guenther @ 2011-09-30 8:56 UTC (permalink / raw)
To: Tom de Vries; +Cc: gcc-patches
On Thu, Sep 29, 2011 at 5:57 PM, Tom de Vries <Tom_deVries@mentor.com> wrote:
> Richard,
>
> in gimplify_vla_decl, the alloca argument seems to be the size of the vla in units:
> ...
> t = build_call_expr (t, 1, DECL_SIZE_UNIT (decl));
> ...
>
> I wonder why we are going through this 8 vs. BITS_PER_UNIT conversion here:
> ...
> elem_type = build_nonstandard_integer_type (BITS_PER_UNIT, 1);
> n_elem = size * 8 / BITS_PER_UNIT;
> align = MIN (size * 8, BIGGEST_ALIGNMENT);
> ...
> The element size is BITS_PER_UNIT, so 1 unit, and size is in units.
No, the size is in bytes and the gimplify code lacks the conversion.
Richard.
>
> Shouldn't this be:
> ...
> Index: tree-ssa-ccp.c
> ===================================================================
> --- tree-ssa-ccp.c (revision 179210)
> +++ tree-ssa-ccp.c (working copy)
> @@ -1722,8 +1722,8 @@ fold_builtin_alloca_for_var (gimple stmt
>
> /* Declare array. */
> elem_type = build_nonstandard_integer_type (BITS_PER_UNIT, 1);
> - n_elem = size * 8 / BITS_PER_UNIT;
> - align = MIN (size * 8, BIGGEST_ALIGNMENT);
> + n_elem = size;
> + align = MIN (size * BITS_PER_UNIT, BIGGEST_ALIGNMENT);
> if (align < BITS_PER_UNIT)
> align = BITS_PER_UNIT;
> array_type = build_array_type_nelts (elem_type, n_elem);
> ...
>
> Thanks,
> - Tom
>
^ permalink raw reply [flat|nested] 2+ messages in thread
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2011-09-29 18:09 argument of alloca in terms of units or not Tom de Vries
2011-09-30 8:56 ` Richard Guenther
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