Regressions on master at commit r15-6177 vs commit r15-6176 on Linux/x86_64

[Haochen Jiang via Gcc-regression]

Regressions on master at commit r15-6177 vs commit r15-6176 on Linux/x86_64
New failures:
FAIL: 30_threads/async/async.cc  -std=gnu++17 execution test

New passes:
FAIL: gcc.dg/lto/save-temps c_lto_save-temps_0.o-c_lto_save-temps_0.o link,  -O 
-flto -save-temps