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re PR middle-end/80341 (gcc miscompiles division of signed char) 

2017-04-07  Richard Biener  <rguenther@suse.de>

	PR middle-end/80341
	* tree.c (get_unwidened): Also handle ! for_type case for
	INTEGER_CSTs.
	* convert.c (do_narrow): Split out from ...
	(convert_to_integer_1): ... here.  Do not pass final truncation
	type to get_unwidened for TRUNC_DIV_EXPR.

	* gcc.dg/torture/pr80341.c: New testcase.

From-SVN: r246756
This commit is contained in:
Richard Biener 2017-04-07 08:20:24 +00:00 committed by Richard Biener
parent 5291ab733b
commit 2d143ba8cf
5 changed files with 136 additions and 75 deletions
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9
gcc/ChangeLog
View File

@ -1,3 +1,12 @@
2017-04-07 Richard Biener <rguenther@suse.de>
PR middle-end/80341
* tree.c (get_unwidened): Also handle ! for_type case for
INTEGER_CSTs.
* convert.c (do_narrow): Split out from ...
(convert_to_integer_1): ... here. Do not pass final truncation
type to get_unwidened for TRUNC_DIV_EXPR.
2017-04-07 Richard Biener <rguenther@suse.de>
* tree-affine.c (wide_int_ext_for_comb): Take type rather

158
gcc/convert.c
View File

@ -413,6 +413,83 @@ convert_to_real_maybe_fold (tree type, tree expr, bool dofold)
return convert_to_real_1 (type, expr, dofold || CONSTANT_CLASS_P (expr));
}
/* Try to narrow EX_FORM ARG0 ARG1 in narrowed arg types producing a
result in TYPE. */
static tree
do_narrow (location_t loc,
enum tree_code ex_form, tree type, tree arg0, tree arg1,
tree expr, unsigned inprec, unsigned outprec, bool dofold)
{
/* Do the arithmetic in type TYPEX,
then convert result to TYPE. */
tree typex = type;
/* Can't do arithmetic in enumeral types
so use an integer type that will hold the values. */
if (TREE_CODE (typex) == ENUMERAL_TYPE)
typex = lang_hooks.types.type_for_size (TYPE_PRECISION (typex),
TYPE_UNSIGNED (typex));
/* But now perhaps TYPEX is as wide as INPREC.
In that case, do nothing special here.
(Otherwise would recurse infinitely in convert. */
if (TYPE_PRECISION (typex) != inprec)
{
/* Don't do unsigned arithmetic where signed was wanted,
or vice versa.
Exception: if both of the original operands were
unsigned then we can safely do the work as unsigned.
Exception: shift operations take their type solely
from the first argument.
Exception: the LSHIFT_EXPR case above requires that
we perform this operation unsigned lest we produce
signed-overflow undefinedness.
And we may need to do it as unsigned
if we truncate to the original size. */
if (TYPE_UNSIGNED (TREE_TYPE (expr))
|| (TYPE_UNSIGNED (TREE_TYPE (arg0))
&& (TYPE_UNSIGNED (TREE_TYPE (arg1))
|| ex_form == LSHIFT_EXPR
|| ex_form == RSHIFT_EXPR
|| ex_form == LROTATE_EXPR
|| ex_form == RROTATE_EXPR))
|| ex_form == LSHIFT_EXPR
/* If we have !flag_wrapv, and either ARG0 or
ARG1 is of a signed type, we have to do
PLUS_EXPR, MINUS_EXPR or MULT_EXPR in an unsigned
type in case the operation in outprec precision
could overflow. Otherwise, we would introduce
signed-overflow undefinedness. */
|| ((!TYPE_OVERFLOW_WRAPS (TREE_TYPE (arg0))
|| !TYPE_OVERFLOW_WRAPS (TREE_TYPE (arg1)))
&& ((TYPE_PRECISION (TREE_TYPE (arg0)) * 2u
> outprec)
|| (TYPE_PRECISION (TREE_TYPE (arg1)) * 2u
> outprec))
&& (ex_form == PLUS_EXPR
|| ex_form == MINUS_EXPR
|| ex_form == MULT_EXPR)))
{
if (!TYPE_UNSIGNED (typex))
typex = unsigned_type_for (typex);
}
else
{
if (TYPE_UNSIGNED (typex))
typex = signed_type_for (typex);
}
/* We should do away with all this once we have a proper
type promotion/demotion pass, see PR45397. */
expr = maybe_fold_build2_loc (dofold, loc, ex_form, typex,
convert (typex, arg0),
convert (typex, arg1));
return convert (type, expr);
}
return NULL_TREE;
}
/* Convert EXPR to some integer (or enum) type TYPE.
EXPR must be pointer, integer, discrete (enum, char, or bool), float,
@ -719,8 +796,8 @@ convert_to_integer_1 (tree type, tree expr, bool dofold)
case TRUNC_DIV_EXPR:
{
tree arg0 = get_unwidened (TREE_OPERAND (expr, 0), type);
tree arg1 = get_unwidened (TREE_OPERAND (expr, 1), type);
tree arg0 = get_unwidened (TREE_OPERAND (expr, 0), NULL_TREE);
tree arg1 = get_unwidened (TREE_OPERAND (expr, 1), NULL_TREE);
/* Don't distribute unless the output precision is at least as
big as the actual inputs and it has the same signedness. */
@ -738,7 +815,12 @@ convert_to_integer_1 (tree type, tree expr, bool dofold)
&& (TYPE_UNSIGNED (TREE_TYPE (arg0))
|| (TREE_CODE (arg1) == INTEGER_CST
&& !integer_all_onesp (arg1))))
goto trunc1;
{
tree tem = do_narrow (loc, ex_form, type, arg0, arg1,
expr, inprec, outprec, dofold);
if (tem)
return tem;
}
break;
}
@ -786,72 +868,10 @@ convert_to_integer_1 (tree type, tree expr, bool dofold)
|| inprec > TYPE_PRECISION (TREE_TYPE (arg0))
|| inprec > TYPE_PRECISION (TREE_TYPE (arg1)))
{
/* Do the arithmetic in type TYPEX,
then convert result to TYPE. */
tree typex = type;
/* Can't do arithmetic in enumeral types
so use an integer type that will hold the values. */
if (TREE_CODE (typex) == ENUMERAL_TYPE)
typex
= lang_hooks.types.type_for_size (TYPE_PRECISION (typex),
TYPE_UNSIGNED (typex));
/* But now perhaps TYPEX is as wide as INPREC.
In that case, do nothing special here.
(Otherwise would recurse infinitely in convert. */
if (TYPE_PRECISION (typex) != inprec)
{
/* Don't do unsigned arithmetic where signed was wanted,
or vice versa.
Exception: if both of the original operands were
unsigned then we can safely do the work as unsigned.
Exception: shift operations take their type solely
from the first argument.
Exception: the LSHIFT_EXPR case above requires that
we perform this operation unsigned lest we produce
signed-overflow undefinedness.
And we may need to do it as unsigned
if we truncate to the original size. */
if (TYPE_UNSIGNED (TREE_TYPE (expr))
|| (TYPE_UNSIGNED (TREE_TYPE (arg0))
&& (TYPE_UNSIGNED (TREE_TYPE (arg1))
|| ex_form == LSHIFT_EXPR
|| ex_form == RSHIFT_EXPR
|| ex_form == LROTATE_EXPR
|| ex_form == RROTATE_EXPR))
|| ex_form == LSHIFT_EXPR
/* If we have !flag_wrapv, and either ARG0 or
ARG1 is of a signed type, we have to do
PLUS_EXPR, MINUS_EXPR or MULT_EXPR in an unsigned
type in case the operation in outprec precision
could overflow. Otherwise, we would introduce
signed-overflow undefinedness. */
|| ((!TYPE_OVERFLOW_WRAPS (TREE_TYPE (arg0))
|| !TYPE_OVERFLOW_WRAPS (TREE_TYPE (arg1)))
&& ((TYPE_PRECISION (TREE_TYPE (arg0)) * 2u
> outprec)
|| (TYPE_PRECISION (TREE_TYPE (arg1)) * 2u
> outprec))
&& (ex_form == PLUS_EXPR
|| ex_form == MINUS_EXPR
|| ex_form == MULT_EXPR)))
{
if (!TYPE_UNSIGNED (typex))
typex = unsigned_type_for (typex);
}
else
{
if (TYPE_UNSIGNED (typex))
typex = signed_type_for (typex);
}
/* We should do away with all this once we have a proper
type promotion/demotion pass, see PR45397. */
expr = maybe_fold_build2_loc (dofold, loc, ex_form, typex,
convert (typex, arg0),
convert (typex, arg1));
return convert (type, expr);
}
tree tem = do_narrow (loc, ex_form, type, arg0, arg1,
expr, inprec, outprec, dofold);
if (tem)
return tem;
}
}
break;

5
gcc/testsuite/ChangeLog
View File

@ -1,3 +1,8 @@
2017-04-07 Richard Biener <rguenther@suse.de>
PR middle-end/80341
* gcc.dg/torture/pr80341.c: New testcase.
2017-04-06 Jakub Jelinek <jakub@redhat.com>
PR debug/80234

19
gcc/testsuite/gcc.dg/torture/pr80341.c Normal file
View File

@ -0,0 +1,19 @@
/* { dg-do run } */
/* { dg-additional-options "-Wno-overflow" } */
const signed char c = -84;
signed char s;
void
foo ()
{
s = (unsigned short) c / -55;
}
int
main ()
{
foo ();
if (s != 90)
__builtin_abort ();
}

20
gcc/tree.c
View File

@ -9033,13 +9033,21 @@ get_unwidened (tree op, tree for_type)
}
}
/* If we finally reach a constant see if it fits in for_type and
/* If we finally reach a constant see if it fits in sth smaller and
in that case convert it. */
if (for_type
&& TREE_CODE (win) == INTEGER_CST
&& TREE_TYPE (win) != for_type
&& int_fits_type_p (win, for_type))
win = fold_convert (for_type, win);
if (TREE_CODE (win) == INTEGER_CST)
{
tree wtype = TREE_TYPE (win);
unsigned prec = wi::min_precision (win, TYPE_SIGN (wtype));
if (for_type)
prec = MAX (prec, final_prec);
if (prec < TYPE_PRECISION (wtype))
{
tree t = lang_hooks.types.type_for_size (prec, TYPE_UNSIGNED (wtype));
if (t && TYPE_PRECISION (t) < TYPE_PRECISION (wtype))
win = fold_convert (t, win);
}
}
return win;
}