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re PR middle-end/79123 (incorrect -Walloca-larger-than: alloca may be too large due to conversion from long int to long unsigned int)

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PR middle-end/79123
	* gimple-ssa-warn-alloca.c (alloca_call_type): Make sure
	casts from signed to unsigned really don't have a range.

From-SVN: r244859
This commit is contained in:
Aldy Hernandez 2017-01-24 09:50:33 +00:00 • committed by Aldy Hernandez
parent cf8e20bfd8
commit 4cd7b1a9e0
3 changed files with 40 additions and 2 deletions
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6
gcc/ChangeLog
View file

@ -1,3 +1,9 @@
2017-01-24 Aldy Hernandez <aldyh@redhat.com>
PR middle-end/79123
* gimple-ssa-warn-alloca.c (alloca_call_type): Make sure
casts from signed to unsigned really don't have a range.
2017-01-24 Markus Trippelsdorf <markus@trippelsdorf.de>
* gimple-ssa-sprintf.c (format_floating): Change MPFR_RNDx to

25
gcc/gimple-ssa-warn-alloca.c
View file

@ -272,6 +272,7 @@ static struct alloca_type_and_limit
alloca_call_type (gimple *stmt, bool is_vla, tree *invalid_casted_type)
{
gcc_assert (gimple_alloca_call_p (stmt));
bool tentative_cast_from_signed = false;
tree len = gimple_call_arg (stmt, 0);
tree len_casted = NULL;
wide_int min, max;
@ -352,8 +353,26 @@ alloca_call_type (gimple *stmt, bool is_vla, tree *invalid_casted_type)
// with this heuristic. Hopefully, this VR_ANTI_RANGE
// nonsense will go away, and we won't have to catch the
// sign conversion problems with this crap.
//
// This is here to catch things like:
// void foo(signed int n) {
// if (n < 100)
// alloca(n);
// ...
// }
if (cast_from_signed_p (len, invalid_casted_type))
return alloca_type_and_limit (ALLOCA_CAST_FROM_SIGNED);
{
// Unfortunately this also triggers:
//
// __SIZE_TYPE__ n = (__SIZE_TYPE__)blah;
// if (n < 100)
// alloca(n);
//
// ...which is clearly bounded. So, double check that
// the paths leading up to the size definitely don't
// have a bound.
tentative_cast_from_signed = true;
}
}
// No easily determined range and try other things.
}
@ -371,10 +390,12 @@ alloca_call_type (gimple *stmt, bool is_vla, tree *invalid_casted_type)
ret = alloca_call_type_by_arg (len, len_casted,
EDGE_PRED (bb, ix), max_size);
if (ret.type != ALLOCA_OK)
return ret;
break;
}
}
if (tentative_cast_from_signed && ret.type != ALLOCA_OK)
return alloca_type_and_limit (ALLOCA_CAST_FROM_SIGNED);
return ret;
}

11
gcc/testsuite/gcc.dg/Walloca-13.c Normal file
View file

@ -0,0 +1,11 @@
/* { dg-do compile } */
/* { dg-options "-Walloca-larger-than=100 -O2" } */
void f (void*);
void g (int *p, int *q)
{
__SIZE_TYPE__ n = (__SIZE_TYPE__)(p - q);
if (n < 100)
f (__builtin_alloca (n));
}