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PR c++/93238 - short right-shift with enum.

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My earlier patch to reintroduce short_shift failed to adjust for the C++
front end use of const_op1 rather than op1.

	* typeck.c (cp_build_binary_op): Use folded op1 for short_shift.
This commit is contained in:
Jason Merrill 2020-01-12 15:09:22 -05:00
parent 33742a0a02
commit f1acad4e43
3 changed files with 18 additions and 3 deletions
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5
gcc/cp/ChangeLog
View file

@ -1,3 +1,8 @@
2020-01-13 Jason Merrill <jason@redhat.com>
PR c++/93238 - short right-shift with enum.
* typeck.c (cp_build_binary_op): Use folded op1 for short_shift.
2020-01-10 Jason Merrill <jason@redhat.com>
* typeck.c (cp_build_binary_op): Restore short_shift code.

8
gcc/cp/typeck.c
View file

@ -4848,7 +4848,7 @@ cp_build_binary_op (const op_location_t &location,
}
else
{
if (!integer_zerop (op1))
if (!integer_zerop (const_op1))
short_shift = 1;
if (compare_tree_int (const_op1, TYPE_PRECISION (type0)) >= 0
@ -5599,6 +5599,7 @@ cp_build_binary_op (const op_location_t &location,
{
int unsigned_arg;
tree arg0 = get_narrower (op0, &unsigned_arg);
tree const_op1 = cp_fold_rvalue (op1);
final_type = result_type;
@ -5606,10 +5607,11 @@ cp_build_binary_op (const op_location_t &location,
unsigned_arg = TYPE_UNSIGNED (TREE_TYPE (op0));
if (TYPE_PRECISION (TREE_TYPE (arg0)) < TYPE_PRECISION (result_type)
&& tree_int_cst_sgn (op1) > 0
&& tree_int_cst_sgn (const_op1) > 0
/* We can shorten only if the shift count is less than the
number of bits in the smaller type size. */
&& compare_tree_int (op1, TYPE_PRECISION (TREE_TYPE (arg0))) < 0
&& compare_tree_int (const_op1,
TYPE_PRECISION (TREE_TYPE (arg0))) < 0
/* We cannot drop an unsigned shift after sign-extension. */
&& (!TYPE_UNSIGNED (final_type) || unsigned_arg))
{

8
gcc/testsuite/g++.dg/expr/rshift1.C Normal file
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@ -0,0 +1,8 @@
// PR c++/93238
short s;
enum { zero };
int fn(int i)
{
return s >> zero;
}