https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91292
--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-11 branch has been updated by Patrick Palka <ppa...@gcc.gnu.org>: https://gcc.gnu.org/g:1682576e62d41cd761472943372b83aee514254a commit r11-9083-g1682576e62d41cd761472943372b83aee514254a Author: Patrick Palka <ppa...@redhat.com> Date: Fri Sep 24 12:36:26 2021 -0400 real: fix encoding of negative IEEE double/quad values [PR98216] In encode_ieee_double/quad, the assignment unsigned long WORD = r->sign << 31; is intended to set the 31st bit of WORD whenever the sign bit is set. But on LP64 hosts it also unintentionally sets the upper 32 bits of WORD, because r->sign gets promoted from unsigned:1 to int and then the result of the shift (equal to INT_MIN) gets sign extended from int to long. In the C++ frontend, this bug causes incorrect mangling of negative floating point values because the output of real_to_target called from write_real_cst unexpectedly has the upper 32 bits of this word set, which the caller doesn't mask out. This patch fixes this by avoiding the unwanted sign extension. Note that r0-53976 fixed the same bug in encode_ieee_single long ago. PR c++/98216 PR c++/91292 gcc/ChangeLog: * real.c (encode_ieee_double): Avoid unwanted sign extension. (encode_ieee_quad): Likewise. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/nontype-float2.C: New test. (cherry picked from commit 34947d4e97ee72b26491cfe5ff4fa8258fadbe95)
