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backport: re PR c++/82781 (Vector extension operators return wrong result in constexpr) 

Backported from mainline
	2017-11-20  Jakub Jelinek  <jakub@redhat.com>

	PR c++/82781
	* constexpr.c (cxx_eval_vector_conditional_expression): New function.
	(cxx_eval_constant_expression) <case VEC_COND_EXPR>: Use it instead
	of cxx_eval_conditional_expression.

	* g++.dg/ext/constexpr-pr82781.C: New test.

From-SVN: r255707
This commit is contained in:
Jakub Jelinek 2017-12-15 22:50:00 +01:00 committed by Jakub Jelinek
parent 8c633e4d27
commit e74d698765
4 changed files with 73 additions and 2 deletions
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10
gcc/cp/ChangeLog
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@ -1,3 +1,13 @@
2017-12-15 Jakub Jelinek <jakub@redhat.com>
Backported from mainline
2017-11-20 Jakub Jelinek <jakub@redhat.com>
PR c++/82781
* constexpr.c (cxx_eval_vector_conditional_expression): New function.
(cxx_eval_constant_expression) <case VEC_COND_EXPR>: Use it instead
of cxx_eval_conditional_expression.
2017-10-30 Paolo Carlini <paolo.carlini@oracle.com>
PR c++/82085

45
gcc/cp/constexpr.c
View File

@ -2044,6 +2044,45 @@ cxx_eval_conditional_expression (const constexpr_ctx *ctx, tree t,
jump_target);
}
/* Subroutine of cxx_eval_constant_expression.
Attempt to evaluate vector condition expressions. Unlike
cxx_eval_conditional_expression, VEC_COND_EXPR acts like a normal
ternary arithmetics operation, where all 3 arguments have to be
evaluated as constants and then folding computes the result from
them. */
static tree
cxx_eval_vector_conditional_expression (const constexpr_ctx *ctx, tree t,
bool *non_constant_p, bool *overflow_p)
{
tree arg1 = cxx_eval_constant_expression (ctx, TREE_OPERAND (t, 0),
/*lval*/false,
non_constant_p, overflow_p);
VERIFY_CONSTANT (arg1);
tree arg2 = cxx_eval_constant_expression (ctx, TREE_OPERAND (t, 1),
/*lval*/false,
non_constant_p, overflow_p);
VERIFY_CONSTANT (arg2);
tree arg3 = cxx_eval_constant_expression (ctx, TREE_OPERAND (t, 2),
/*lval*/false,
non_constant_p, overflow_p);
VERIFY_CONSTANT (arg3);
location_t loc = EXPR_LOCATION (t);
tree type = TREE_TYPE (t);
tree r = fold_ternary_loc (loc, VEC_COND_EXPR, type, arg1, arg2, arg3);
if (r == NULL_TREE)
{
if (arg1 == TREE_OPERAND (t, 0)
&& arg2 == TREE_OPERAND (t, 1)
&& arg3 == TREE_OPERAND (t, 2))
r = t;
else
r = build3_loc (loc, VEC_COND_EXPR, type, arg1, arg2, arg3);
}
VERIFY_CONSTANT (r);
return r;
}
/* Returns less than, equal to, or greater than zero if KEY is found to be
less than, to match, or to be greater than the constructor_elt's INDEX. */
@ -4361,12 +4400,14 @@ cxx_eval_constant_expression (const constexpr_ctx *ctx, tree t,
jump_target);
break;
}
/* FALLTHRU */
case VEC_COND_EXPR:
r = cxx_eval_conditional_expression (ctx, t, lval,
non_constant_p, overflow_p,
jump_target);
break;
case VEC_COND_EXPR:
r = cxx_eval_vector_conditional_expression (ctx, t, non_constant_p,
overflow_p);
break;
case CONSTRUCTOR:
if (TREE_CONSTANT (t))

8
gcc/testsuite/ChangeLog
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@ -1,3 +1,11 @@
2017-12-15 Jakub Jelinek <jakub@redhat.com>
Backported from mainline
2017-11-20 Jakub Jelinek <jakub@redhat.com>
PR c++/82781
* g++.dg/ext/constexpr-pr82781.C: New test.
2017-12-15 Richard Biener <rguenther@suse.de>
Backport from mainline

12
gcc/testsuite/g++.dg/ext/constexpr-pr82781.C Normal file
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@ -0,0 +1,12 @@
// PR c++/82781
// { dg-do compile { target c++11 } }
typedef int V __attribute__ ((vector_size (16)));
constexpr V b1 = { 0, 1, 10, 20 };
constexpr V b2 = { 0, 2, 10, 0 };
constexpr V b3 = b1 == b2;
static_assert (b3[0] == -1, "");
static_assert (b3[1] == 0, "");
static_assert (b3[2] == -1, "");
static_assert (b3[3] == 0, "");