Regressions on master at commit r17-2153 vs commit r17-2139 on Linux/x86_64

[Haochen Jiang via Gcc-regression]

Regressions on master at commit r17-2153 vs commit r17-2139 on Linux/x86_64
New failures:

New passes:
FAIL: gfortran.dg/warn_undefined_vars_6.f90   -O  (test for excess errors)
FAIL: gfortran.dg/warn_undefined_vars_6.f90   -O  (test for excess errors)