procyberian/gcc
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

tree-ssa-forwprop.c (associate_plusminus): For widening conversions check for undefined overflow in (T)(P + A) - (T)P -> (T)A.

Browse source 
2014-06-25  Bernd Edlinger  <bernd.edlinger@hotmail.de>

        * tree-ssa-forwprop.c (associate_plusminus): For widening conversions
        check for undefined overflow in (T)(P + A) - (T)P -> (T)A.
        Issue a strict overflow warning if appropriate.

testsuite:
2014-06-25  Bernd Edlinger  <bernd.edlinger@hotmail.de>

        * gcc.c-torture/execute/20140622-1.c: New test.

From-SVN: r211988
This commit is contained in:
Bernd Edlinger 2014-06-25 17:24:34 +00:00 • committed by Bernd Edlinger
parent d122681a3c
commit f9bb13f37b
4 changed files with 65 additions and 7 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

6
gcc/ChangeLog
View file

@ -1,3 +1,9 @@
2014-06-25 Bernd Edlinger <bernd.edlinger@hotmail.de>
* tree-ssa-forwprop.c (associate_plusminus): For widening conversions
check for undefined overflow in (T)(P + A) - (T)P -> (T)A.
Issue a strict overflow warning if appropriate.
2014-06-25 Martin Liska <mliska@suse.cz>
IPA REF refactoring

4
gcc/testsuite/ChangeLog
View file

@ -1,3 +1,7 @@
2014-06-25 Bernd Edlinger <bernd.edlinger@hotmail.de>
* gcc.c-torture/execute/20140622-1.c: New test.
2014-06-25 Paolo Carlini <paolo.carlini@oracle.com>
DR 178

27
gcc/testsuite/gcc.c-torture/execute/20140622-1.c Normal file
View file

@ -0,0 +1,27 @@
unsigned p;
long __attribute__((noinline, noclone))
test (unsigned a)
{
return (long)(p + a) - (long)p;
}
int
main ()
{
p = (unsigned) -2;
if (test (0) != 0)
__builtin_abort ();
if (test (1) != 1)
__builtin_abort ();
if (test (2) != -(long)(unsigned)-2)
__builtin_abort ();
p = (unsigned) -1;
if (test (0) != 0)
__builtin_abort ();
if (test (1) != -(long)(unsigned)-1)
__builtin_abort ();
if (test (2) != -(long)(unsigned)-2)
__builtin_abort ();
return 0;
}

35
gcc/tree-ssa-forwprop.c
View file

@ -47,6 +47,7 @@ along with GCC; see the file COPYING3. If not see
#include "tree-pass.h"
#include "langhooks.h"
#include "flags.h"
#include "diagnostic.h"
#include "expr.h"
#include "cfgloop.h"
#include "optabs.h"
@ -2666,15 +2667,35 @@ associate_plusminus (gimple_stmt_iterator *gsi)
{
/* And finally (T)(P + A) - (T)P. */
tree a = gimple_assign_rhs2 (def_stmt2);
/* For pointer types, if the conversion of A to the final
type requires a sign- or zero-extension, then we have
to punt - it is not defined which one is correct. */
if (!POINTER_TYPE_P (TREE_TYPE (rhs1))
|| TYPE_PRECISION (TREE_TYPE (rhs1))
<= TYPE_PRECISION (TREE_TYPE (a))
|| (TREE_CODE (a) == INTEGER_CST
if (TYPE_PRECISION (TREE_TYPE (rhs1))
<= TYPE_PRECISION (TREE_TYPE (a))
/* For integer types, if A has a smaller type
than T the result depends on the possible
overflow in P + A.
E.g. T=size_t, A=(unsigned)429497295, P>0.
However, if an overflow in P + A would cause
undefined behavior, we can assume that there
is no overflow. */
|| (INTEGRAL_TYPE_P (TREE_TYPE (p))
&& TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (p)))
/* For pointer types, if the conversion of A to the
final type requires a sign- or zero-extension,
then we have to punt - it is not defined which
one is correct. */
|| (POINTER_TYPE_P (TREE_TYPE (p))
&& TREE_CODE (a) == INTEGER_CST
&& tree_int_cst_sign_bit (a) == 0))
{
if (issue_strict_overflow_warning
(WARN_STRICT_OVERFLOW_MISC)
&& TYPE_PRECISION (TREE_TYPE (rhs1))
> TYPE_PRECISION (TREE_TYPE (a))
&& INTEGRAL_TYPE_P (TREE_TYPE (p)))
warning_at (gimple_location (stmt),
OPT_Wstrict_overflow,
"assuming signed overflow does not "
"occur when assuming that "
"(T)(P + A) - (T)P is always (T)A");
if (useless_type_conversion_p (TREE_TYPE (rhs1),
TREE_TYPE (a)))
code = TREE_CODE (a);