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Fix UB in int_const_binop

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When testing PR 85164, the baseline bootstrap-ubsan results had
a lot of failures from int_const_binop.  This is because with the
new overflow handling we can sometimes do:

      poly_res = res;

on an uninitialised res.

2019-04-18  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* fold-const.c (int_const_binop): Return early on failure.

From-SVN: r270443
This commit is contained in:
Richard Sandiford 2019-04-18 12:30:36 +00:00 • committed by Richard Sandiford
parent cd7f7c54a4
commit 714996e2c2
2 changed files with 14 additions and 10 deletions
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4
gcc/ChangeLog
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@ -1,3 +1,7 @@
2019-04-18 Richard Sandiford <richard.sandiford@arm.com>
* fold-const.c (int_const_binop): Return early on failure.
2019-04-18 Richard Sandiford <richard.sandiford@arm.com>
PR middle-end/85164

20
gcc/fold-const.c
View file

@ -1173,7 +1173,6 @@ tree
int_const_binop (enum tree_code code, const_tree arg1, const_tree arg2,
int overflowable)
{
bool success = false;
poly_wide_int poly_res;
tree type = TREE_TYPE (arg1);
signop sign = TYPE_SIGN (type);
@ -1183,17 +1182,18 @@ int_const_binop (enum tree_code code, const_tree arg1, const_tree arg2,
{
wide_int warg1 = wi::to_wide (arg1), res;
wide_int warg2 = wi::to_wide (arg2, TYPE_PRECISION (type));
success = wide_int_binop (res, code, warg1, warg2, sign, &overflow);
if (!wide_int_binop (res, code, warg1, warg2, sign, &overflow))
return NULL_TREE;
poly_res = res;
}
else if (poly_int_tree_p (arg1) && poly_int_tree_p (arg2))
success = poly_int_binop (poly_res, code, arg1, arg2, sign, &overflow);
if (success)
return force_fit_type (type, poly_res, overflowable,
(((sign == SIGNED || overflowable == -1)
&& overflow)
| TREE_OVERFLOW (arg1) | TREE_OVERFLOW (arg2)));
return NULL_TREE;
else if (!poly_int_tree_p (arg1)
|| !poly_int_tree_p (arg2)
|| !poly_int_binop (poly_res, code, arg1, arg2, sign, &overflow))
return NULL_TREE;
return force_fit_type (type, poly_res, overflowable,
(((sign == SIGNED || overflowable == -1)
&& overflow)
| TREE_OVERFLOW (arg1) | TREE_OVERFLOW (arg2)));
}
/* Return true if binary operation OP distributes over addition in operand