https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82071
--- Comment #4 from Joseph S. Myers <jsm28 at gcc dot gnu.org> --- Author: jsm28 Date: Fri Sep 15 20:49:02 2017 New Revision: 252847 URL: https://gcc.gnu.org/viewcvs?rev=252847&root=gcc&view=rev Log: Implement C11 excess precision semantics for conversions (PR c/82071). C11 semantics for excess precision (from N1531) are that an implicit conversion (from the usual arithmetic conversions, not by assignment) from integer to floating point has a result in the corresponding evaluation format of that floating-point type, so possibly with excess precision (whereas a cast or conversion by assignment from integer to floating point must produce a value without excess range or precision, as always). This patch makes GCC support those semantics if flag_isoc11 (which in turn means that conditional expressions need to support generating a result with excess precision even if neither operand had excess precision). C99 is less than entirely clear in this regard, but my reading as outlined at <https://gcc.gnu.org/ml/gcc-patches/2008-11/msg00105.html> is that the results of conversions from integer to floating-point types are always expected to be representable in the target type without excess precision, and this patch conservatively keeps these semantics for pre-C11 (i.e. if an older standard is explicitly selected). Bootstrapped with no regressions on x86_64-pc-linux-gnu. PR c/82071 gcc/c: * c-typeck.c (ep_convert_and_check): Just call convert_and_check for C11. (build_conditional_expr): For C11, generate result with excess precision when one argument is an integer and the other is of a type using excess precision. gcc/testsuite: * gcc.target/i386/excess-precision-8.c: New test. Added: trunk/gcc/testsuite/gcc.target/i386/excess-precision-8.c Modified: trunk/gcc/c/ChangeLog trunk/gcc/c/c-typeck.c trunk/gcc/testsuite/ChangeLog
