re PR c++/71537 (GCC rejects consetxpr boolean conversions and comparisons on the result of pointer arithmetic.)

2016-12-06  Jakub Jelinek  <jakub@redhat.com>

	PR c++/71537
	* fold-const-call.c (fold_const_call_1): Remove memchr handling here.
	(fold_const_call) <case CFN_BUILT_IN_STRNCMP,
	case CFN_BUILT_IN_STRNCASECMP>: Formatting improvements.
	(fold_const_call) <case CFN_BUILT_IN_MEMCMP>: Likewise.  If s2 is 0
	and arguments have no side-effects, return 0.
	(fold_const_call): Handle CFN_BUILT_IN_MEMCHR.

	* g++.dg/cpp0x/constexpr-memchr.C: New test.

From-SVN: r243285