Re: Fix PR57886, invalid folding of conversion
Hi, On Fri, 12 Jul 2013, Marc Glisse wrote: > If you want to handle integers, shouldn't you test TYPE_OVERFLOW_UNDEFINED > (for LONG_MIN)? Right, ... > FLOAT_TYPE_P does seem safer indeed. ... hence this is it now. > > I'd replace TREE_TYPE (expr) with itype on the next line, it is confusing to > refer to it under 2 different names on 2 consecutive lines. True, I made that change. r200926. Ciao, Michael.
Re: Fix PR57886, invalid folding of conversion
On Fri, 12 Jul 2013, Michael Matz wrote: GCC happily transforms (float)-z into -(float)z, even when z is of unsigned type (when it's larger than float). That's wrong (the result should always be positive, because -z is). It seems to me that this bug exists in all reasonably recent GCC versions. The checking in convert_to_real is wrong, it compares type precisions of different classed types. The change with the least impact is to reject only TYPE_UNSIGNED inner types, but perhaps it would be better to only do the transformation if the inner type is FLOAT_TYPE_P as well. If you want to handle integers, shouldn't you test TYPE_OVERFLOW_UNDEFINED (for LONG_MIN)? FLOAT_TYPE_P does seem safer indeed. I'd replace TREE_TYPE (expr) with itype on the next line, it is confusing to refer to it under 2 different names on 2 consecutive lines. -- Marc Glisse
Re: Fix PR57886, invalid folding of conversion
On Fri, Jul 12, 2013 at 03:37:44PM +0200, Michael Matz wrote: > So, this is a dup of PR55771, I'm now proposing to add a test for > FLOAT_TYPE_P, not TYPE_UNSIGNED. Restarted the regstrap. Ok if it passes bootstrap/regtest. I'd say we should apply it to 4.8 too, while it might not be a regression (or at least not a recent one), it is a silent wrong-code issue. Sorry for forgetting about this PR. > PR middle-end/55771 > * convert.c (convert_to_real): Reject non-float inner types. > > testsuite/ > * c-c++-common/pr55771.c: New test. Jakub
Re: Fix PR57886, invalid folding of conversion
Hi,
On Fri, 12 Jul 2013, Michael Matz wrote:
> Hi,
>
> GCC happily transforms (float)-z into -(float)z, even when z is of
> unsigned type (when it's larger than float). That's wrong (the result
> should always be positive, because -z is). It seems to me that this bug
> exists in all reasonably recent GCC versions. The checking in
> convert_to_real is wrong, it compares type precisions of different
> classed types. The change with the least impact is to reject only
> TYPE_UNSIGNED inner types, but perhaps it would be better to only do the
> transformation if the inner type is FLOAT_TYPE_P as well.
So, this is a dup of PR55771, I'm now proposing to add a test for
FLOAT_TYPE_P, not TYPE_UNSIGNED. Restarted the regstrap.
Ciao,
Michael.
--
PR middle-end/55771
* convert.c (convert_to_real): Reject non-float inner types.
testsuite/
* c-c++-common/pr55771.c: New test.
Index: convert.c
===
--- convert.c (revision 200240)
+++ convert.c (working copy)
@@ -213,10 +213,11 @@ convert_to_real (tree type, tree expr)
switch (TREE_CODE (expr))
{
/* Convert (float)-x into -(float)x. This is safe for
- round-to-nearest rounding mode. */
+ round-to-nearest rounding mode when the inner type is float. */
case ABS_EXPR:
case NEGATE_EXPR:
if (!flag_rounding_math
+ && FLOAT_TYPE_P (itype)
&& TYPE_PRECISION (type) < TYPE_PRECISION (TREE_TYPE (expr)))
return build1 (TREE_CODE (expr), type,
fold (convert_to_real (type,
Index: testsuite/c-c++-common/pr55771.c
===
--- testsuite/c-c++-common/pr55771.c(revision 0)
+++ testsuite/c-c++-common/pr55771.c(working copy)
@@ -0,0 +1,12 @@
+/* { dg-do run } */
+
+float global;
+int main()
+{
+ unsigned long z = 1;
+ float x = -z;
+ global = x;
+ if (global < 0)
+__builtin_abort ();
+ return 0;
+}
Fix PR57886, invalid folding of conversion
Hi,
GCC happily transforms (float)-z into -(float)z, even when z is of
unsigned type (when it's larger than float). That's wrong (the result
should always be positive, because -z is). It seems to me that this bug
exists in all reasonably recent GCC versions. The checking in
convert_to_real is wrong, it compares type precisions of different
classed types. The change with the least impact is to reject only
TYPE_UNSIGNED inner types, but perhaps it would be better to only do the
transformation if the inner type is FLOAT_TYPE_P as well.
Regstrapping on x86-64 in progress. Okay for trunk?
Ciao,
Michael.
PR middle-end/57886
* convert.c (convert_to_real): Reject unsigned inner types.
testsuite/
* c-c++-common/pr57886.c: New test.
Index: convert.c
===
--- convert.c (revision 200240)
+++ convert.c (working copy)
@@ -213,10 +213,11 @@ convert_to_real (tree type, tree expr)
switch (TREE_CODE (expr))
{
/* Convert (float)-x into -(float)x. This is safe for
- round-to-nearest rounding mode. */
+ round-to-nearest rounding mode when the inner type is signed. */
case ABS_EXPR:
case NEGATE_EXPR:
if (!flag_rounding_math
+ && !TYPE_UNSIGNED (itype)
&& TYPE_PRECISION (type) < TYPE_PRECISION (TREE_TYPE (expr)))
return build1 (TREE_CODE (expr), type,
fold (convert_to_real (type,
Index: testsuite/c-c++-common/pr57886.c
===
--- testsuite/c-c++-common/pr57886.c(revision 0)
+++ testsuite/c-c++-common/pr57886.c(working copy)
@@ -0,0 +1,12 @@
+/* { dg-do run } */
+
+float global;
+int main()
+{
+ unsigned long z = 1;
+ float x = -z;
+ global = x;
+ if (global < 0)
+__builtin_abort ();
+ return 0;
+}
