[Bug c++/109359] [12/13 Regression] Compile-time rounding of double literal to float is incorrect with -frounding-math

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109359

--- Comment #12 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Jason Merrill
<jason@gcc.gnu.org>:

https://gcc.gnu.org/g:470f501f31a4bdb9fa04c691ca7db2915ac3ae5b

commit r12-10136-g470f501f31a4bdb9fa04c691ca7db2915ac3ae5b
Author: Jason Merrill <jason@redhat.com>
Date:   Thu Jun 1 14:41:07 2023 -0400

    varasm: check float size [PR109359]

    In PR95226, the testcase was failing because we tried to output_constant a
    NOP_EXPR to float from a double REAL_CST, and so we output a double where
    the caller wanted a float.  That doesn't happen anymore, but with the
    output_constant hunk we will ICE in that situation rather than emit the
    wrong number of bytes.

    Part of the problem was that initializer_constant_valid_p_1 returned true
    for that NOP_EXPR, because it compared the sizes of integer types but not
    floating-point types.  So the C++ front end assumed it didn't need to fold
    the initializer.

    This also fixed the test for PR109359.

            PR c++/95226
            PR c++/109359

    gcc/ChangeLog:

            * varasm.cc (output_constant) [REAL_TYPE]: Check that sizes match.
            (initializer_constant_valid_p_1): Compare float precision.

    gcc/testsuite/ChangeLog:

            * g++.dg/ext/frounding-math1.C: New test.

    (cherry picked from commit e7cc4d703bceb9095316c106eba0d1939c6c8044)