Hi!
VEC_COND_EXPR is handled in constexpr code like COND_EXPR, but that is
wrong. VEC_COND_EXPR is more like an arbitrary arithmetics ternary
operation, we need to compute all 3 arguments and based on the elements of
the first argument pick up elements of 2nd and 3rd arguments.
The COND_EXPR handling just checks the whole first argument, not its
elements, and only evaluates one of the arguments.
Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
trunk and release branches?
2017-11-20 Jakub Jelinek <ja...@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.
--- gcc/cp/constexpr.c.jj 2017-11-14 09:06:48.000000000 +0100
+++ gcc/cp/constexpr.c 2017-11-16 19:43:16.133854557 +0100
@@ -2086,6 +2086,41 @@ cxx_eval_conditional_expression (const c
jump_target);
}
+/* Subroutine of cxx_eval_constant_expression.
+ Attempt to evaluate vector condition expressions. */
+
+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. */
@@ -4398,12 +4433,14 @@ cxx_eval_constant_expression (const cons
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))
--- gcc/testsuite/g++.dg/ext/constexpr-pr82781.C.jj 2017-11-16
19:47:27.547966754 +0100
+++ gcc/testsuite/g++.dg/ext/constexpr-pr82781.C 2017-11-16
19:46:21.000000000 +0100
@@ -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, "");
Jakub
