Regressions on master at commit r15-2811 vs commit r15-2808 on Linux/x86_64

[Haochen Jiang via Gcc-regression]

Regressions on master at commit r15-2811 vs commit r15-2808 on Linux/x86_64
New failures:
FAIL: gfortran.dg/sizeof_6.f90   -O1  execution test

New passes:
FAIL: 30_threads/async/async.cc  -std=gnu++17 execution test