On Tue, Sep 1, 2015 at 12:23 PM, Sujoy Saraswati <ssarasw...@gmail.com> wrote:
> The following patch fixes 61441. It converts sNaN to qNaN on folding
> when -fno-signaling-nans is used.
>
> Bootstrap and regression tests on x86_64-linux-gnu and
> aarch64-unknown-linux-gnu passed with changes done on trunk.
>
> Is this fix fine ?
Note that I'm curious what
the actual bug is - is it that (double) sNaN creates a sNaN? Then the fix
should be elsewhere, in constant folding itself
(fold_convert_const_real_from_real
or real_convert).
If that isn't the bug you have very many other passes to fix for the
same problem.
So - can you please explain?
Thanks,
Richard.
> Regards,
> Sujoy
>
> 2015-09-01 Sujoy Saraswati <ssarasw...@gmail.com>
>
> PR tree-optimization/61441
> * tree-ssa-ccp.c (convert_snan_to_qnan): Convert sNaN to qNaN when
> flag_signaling_nans is off.
> (ccp_fold_stmt, visit_assignment, visit_cond_stmt): call
> convert_snan_to_qnan to convert sNaN to qNaN on constant folding.
>
> PR tree-optimization/61441
> * gcc.dg/pr61441.c: New testcase.
>
> Index: gcc/tree-ssa-ccp.c
> ===================================================================
> --- gcc/tree-ssa-ccp.c (revision 226965)
> +++ gcc/tree-ssa-ccp.c (working copy)
> @@ -560,6 +560,24 @@ value_to_wide_int (ccp_prop_value_t val)
> return 0;
> }
>
> +/* Convert sNaN to qNaN when flag_signaling_nans is off */
> +
> +static void
> +convert_snan_to_qnan (tree expr)
> +{
> + if (expr
> + && (TREE_CODE (expr) == REAL_CST)
> + && !flag_signaling_nans)
> + {
> + REAL_VALUE_TYPE *d = TREE_REAL_CST_PTR (expr);
> +
> + if (HONOR_NANS (TYPE_MODE (TREE_TYPE (expr)))
> + && REAL_VALUE_ISNAN (*d)
> + && d->signalling)
> + d->signalling = 0;
> + }
> +}
> +
> /* Return the value for the address expression EXPR based on alignment
> information. */
>
> @@ -2156,6 +2174,7 @@ ccp_fold_stmt (gimple_stmt_iterator *gsi)
> if (val.lattice_val != CONSTANT
> || val.mask != 0)
> return false;
> + convert_snan_to_qnan (val.value);
>
> if (dump_file)
> {
> @@ -2197,7 +2216,10 @@ ccp_fold_stmt (gimple_stmt_iterator *gsi)
> bool res;
> if (!useless_type_conversion_p (TREE_TYPE (lhs),
> TREE_TYPE (new_rhs)))
> + {
> new_rhs = fold_convert (TREE_TYPE (lhs), new_rhs);
> + convert_snan_to_qnan (new_rhs);
> + }
> res = update_call_from_tree (gsi, new_rhs);
> gcc_assert (res);
> return true;
> @@ -2216,6 +2238,7 @@ ccp_fold_stmt (gimple_stmt_iterator *gsi)
> tree new_rhs = fold_builtin_alloca_with_align (stmt);
> if (new_rhs)
> {
> + convert_snan_to_qnan (new_rhs);
> bool res = update_call_from_tree (gsi, new_rhs);
> tree var = TREE_OPERAND (TREE_OPERAND (new_rhs, 0),0);
> gcc_assert (res);
> @@ -2260,7 +2283,10 @@ ccp_fold_stmt (gimple_stmt_iterator *gsi)
> {
> tree rhs = unshare_expr (val);
> if (!useless_type_conversion_p (TREE_TYPE (lhs), TREE_TYPE (rhs)))
> + {
> rhs = fold_build1 (VIEW_CONVERT_EXPR, TREE_TYPE (lhs), rhs);
> + convert_snan_to_qnan (rhs);
> + }
> gimple_assign_set_rhs_from_tree (gsi, rhs);
> return true;
> }
> @@ -2292,6 +2318,7 @@ visit_assignment (gimple stmt, tree *output_p)
> /* Evaluate the statement, which could be
> either a GIMPLE_ASSIGN or a GIMPLE_CALL. */
> val = evaluate_stmt (stmt);
> + convert_snan_to_qnan (val.value);
>
> /* If STMT is an assignment to an SSA_NAME, we only have one
> value to set. */
> @@ -2324,6 +2351,7 @@ visit_cond_stmt (gimple stmt, edge *taken_edge_p)
> if (val.lattice_val != CONSTANT
> || val.mask != 0)
> return SSA_PROP_VARYING;
> + convert_snan_to_qnan (val.value);
>
> /* Find which edge out of the conditional block will be taken and add it
> to the worklist. If no single edge can be determined statically,
>
> Index: gcc/testsuite/gcc.dg/pr61441.c
> ===================================================================
> --- gcc/testsuite/gcc.dg/pr61441.c (revision 0)
> +++ gcc/testsuite/gcc.dg/pr61441.c (working copy)
> @@ -0,0 +1,17 @@
> +/* { dg-do run } */
> +/* { dg-options "-O1 -lm" } */
> +
> +#define _GNU_SOURCE
> +#include <stdio.h>
> +#include <math.h>
> +
> +int main (void)
> +{
> + float sNaN = __builtin_nansf ("");
> + double x = (double) sNaN;
> + if (issignaling(x))
> + {
> + __builtin_abort();
> + }
> + return 0;
> +}
