[r13-2303 Regression] FAIL: g++.dg/tree-ssa/empty-loop.C -std=gnu++20 (test for excess errors) on Linux/x86_64

[haochen.jiang]

On Linux/x86_64,

b911ca4231a366ddfd026f190b126bd517f4e640 is the first bad commit
commit b911ca4231a366ddfd026f190b126bd517f4e640
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Fri Aug 26 16:22:21 2022 +0100

    libstdc++: Add [[nodiscard]] attribute to <string> and <string_view>

caused

FAIL: g++.dg/tree-ssa/empty-loop.C  -std=gnu++17 (test for excess errors)
FAIL: g++.dg/tree-ssa/empty-loop.C  -std=gnu++20 (test for excess errors)

with GCC configured with

../../gcc/configure --prefix=/export/users/haochenj/src/gcc-bisect/master/master/r13-2303/usr --enable-clocale=gnu --with-system-zlib --with-demangler-in-ld --with-fpmath=sse --enable-languages=c,c++,fortran --enable-cet --without-isl --enable-libmpx x86_64-linux --disable-bootstrap

To reproduce:

$ cd {build_dir}/gcc && make check RUNTESTFLAGS="dg.exp=g++.dg/tree-ssa/empty-loop.C --target_board='unix{-m32}'"
$ cd {build_dir}/gcc && make check RUNTESTFLAGS="dg.exp=g++.dg/tree-ssa/empty-loop.C --target_board='unix{-m32\ -march=cascadelake}'"
$ cd {build_dir}/gcc && make check RUNTESTFLAGS="dg.exp=g++.dg/tree-ssa/empty-loop.C --target_board='unix{-m64}'"
$ cd {build_dir}/gcc && make check RUNTESTFLAGS="dg.exp=g++.dg/tree-ssa/empty-loop.C --target_board='unix{-m64\ -march=cascadelake}'"

(Please do not reply to this email, for question about this report, contact me at haochen dot jiang at intel.com)