On 23/07/15 12:16, Richard Biener wrote:
On Thu, 23 Jul 2015, Kyrill Tkachov wrote:
On 21/07/15 11:11, Richard Biener wrote:
On Tue, 21 Jul 2015, Kyrill Tkachov wrote:
On 21/07/15 08:24, Richard Biener wrote:
On Mon, 20 Jul 2015, Kyrill Tkachov wrote:
Hi all,
This patch fixes the PR in question which is a miscompilation of
gcc.dg/fixed-point/unary.c on arm.
It just restricts the A - B -> A + (-B) transformation when the type
is
fixed-point.
This fixes the testcase for me.
Is this the right approach?
Bootstrap and test on arm and x86 running.
Ok if testing is clean?
Ok, but I think the fold-const.c code has the same issue, no:
/* A - B -> A + (-B) if B is easily negatable. */
if (negate_expr_p (arg1)
&& !TYPE_OVERFLOW_SANITIZED (type)
&& ((FLOAT_TYPE_P (type)
/* Avoid this transformation if B is a positive
REAL_CST.
*/
&& (TREE_CODE (arg1) != REAL_CST
|| REAL_VALUE_NEGATIVE (TREE_REAL_CST (arg1))))
|| INTEGRAL_TYPE_P (type)))
return fold_build2_loc (loc, PLUS_EXPR, type,
fold_convert_loc (loc, type, arg0),
fold_convert_loc (loc, type,
negate_expr (arg1)));
ah, no. The above only applies to float-type and integral-types.
Thus yes, your patch is ok. Can you double-check the other pattern,
/* -(A + B) -> (-B) - A. */
(simplify
(negate (plus:c @0 negate_expr_p@1))
(if (!HONOR_SIGN_DEPENDENT_ROUNDING (element_mode (type))
&& !HONOR_SIGNED_ZEROS (element_mode (type)))
(minus (negate @1) @0)))
?
Thanks, committed with r226028.
I can add (FLOAT_TYPE_P (type) || INTEGRAL_TYPE_P (type)) to the
condition.
That would more closely mirror the original logic, right?
That passes x86_64 bootstrap and aarch64 testing looks ok.
Yeah, that works for me, too.
How about this patch then?
Bootstrapped and tested on x86_64 and aarch64.
Hmm. The code already pretty much matches the one in fold-const.c.
So what's the actual issue with fixed-point types and
-(A + B) -> -B - A iff negate_expr_p says that B can be
safely negated?
That is, can you add a testcase that fails without the patch?
I don't have such a testcase.
If negate_expr_p does what we want here, then I suppose it's redundant
and I withdraw the patch.
I'm not very familiar with the fold-const.c code...
Kyrill
Thanks
Richard.
