On Fri, Sep 30, 2011 at 10:56 AM, Jakub Jelinek <ja...@redhat.com> wrote:
> Hi!
>
> On Fri, Sep 30, 2011 at 10:34:28AM +0200, Richard Guenther wrote:
>> Hmm, I don't think this change is ok. We rely on maybe_fold_reference
>> to re-fold mem-refs to valid gimple form (from propagating say
>> &a.b.c to MEM[p, 4] which first gives the invalid MEM[&a.b.c, 4] and
>> then the folding changes this to MEM[&a, 12]). You need to preserve that
>> and only disable constant folding.
>>
>> Thus I suggest to add a parameter to maybe_fold_reference that says
>> whether to try constant folding (we already have is_lhs, so why not
>> use that?)
>
> So like this instead?
Yes. That's ok if it passes testing.
Thanks,
Richard.
> 2011-09-30 Jakub Jelinek <ja...@redhat.com>
>
> PR inline-asm/50571
> * gimple-fold.c (fold_stmt_1) <case GIMPLE_ASM>: If
> input constraints allow mem and not reg, pass true instead of
> false as second argument to maybe_fold_reference.
>
> * gcc.dg/pr50571.c: New test.
>
> --- gcc/gimple-fold.c.jj 2011-09-29 14:25:46.000000000 +0200
> +++ gcc/gimple-fold.c 2011-09-30 10:54:10.000000000 +0200
> @@ -1201,28 +1201,45 @@ fold_stmt_1 (gimple_stmt_iterator *gsi,
>
> case GIMPLE_ASM:
> /* Fold *& in asm operands. */
> - for (i = 0; i < gimple_asm_noutputs (stmt); ++i)
> - {
> - tree link = gimple_asm_output_op (stmt, i);
> - tree op = TREE_VALUE (link);
> - if (REFERENCE_CLASS_P (op)
> - && (op = maybe_fold_reference (op, true)) != NULL_TREE)
> - {
> - TREE_VALUE (link) = op;
> - changed = true;
> - }
> - }
> - for (i = 0; i < gimple_asm_ninputs (stmt); ++i)
> - {
> - tree link = gimple_asm_input_op (stmt, i);
> - tree op = TREE_VALUE (link);
> - if (REFERENCE_CLASS_P (op)
> - && (op = maybe_fold_reference (op, false)) != NULL_TREE)
> - {
> - TREE_VALUE (link) = op;
> - changed = true;
> - }
> - }
> + {
> + size_t noutputs;
> + const char **oconstraints;
> + const char *constraint;
> + bool allows_mem, allows_reg;
> +
> + noutputs = gimple_asm_noutputs (stmt);
> + oconstraints = XALLOCAVEC (const char *, noutputs);
> +
> + for (i = 0; i < gimple_asm_noutputs (stmt); ++i)
> + {
> + tree link = gimple_asm_output_op (stmt, i);
> + tree op = TREE_VALUE (link);
> + oconstraints[i]
> + = TREE_STRING_POINTER (TREE_VALUE (TREE_PURPOSE (link)));
> + if (REFERENCE_CLASS_P (op)
> + && (op = maybe_fold_reference (op, true)) != NULL_TREE)
> + {
> + TREE_VALUE (link) = op;
> + changed = true;
> + }
> + }
> + for (i = 0; i < gimple_asm_ninputs (stmt); ++i)
> + {
> + tree link = gimple_asm_input_op (stmt, i);
> + tree op = TREE_VALUE (link);
> + constraint
> + = TREE_STRING_POINTER (TREE_VALUE (TREE_PURPOSE (link)));
> + parse_input_constraint (&constraint, 0, 0, noutputs, 0,
> + oconstraints, &allows_mem, &allows_reg);
> + if (REFERENCE_CLASS_P (op)
> + && (op = maybe_fold_reference (op, !allows_reg && allows_mem))
> + != NULL_TREE)
> + {
> + TREE_VALUE (link) = op;
> + changed = true;
> + }
> + }
> + }
> break;
>
> case GIMPLE_DEBUG:
> --- gcc/testsuite/gcc.dg/pr50571.c.jj 2011-09-29 21:28:05.000000000 +0200
> +++ gcc/testsuite/gcc.dg/pr50571.c 2011-09-29 21:30:08.000000000 +0200
> @@ -0,0 +1,11 @@
> +/* PR inline-asm/50571 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2" } */
> +
> +static const int var[4] = { 1, 2, 3, 4 };
> +
> +void
> +foo (void)
> +{
> + __asm volatile ("" : : "m" (*(int *) var));
> +}
>
>
> Jakub
>
