Regressions on native/master at commit r15-1807 vs commit r15-1803 on Linux/x86_64

[Haochen Jiang]

Regressions on master at commit r15-1807 vs commit r15-1803 on Linux/x86_64
New failures:
FAIL: gcc.dg/guality/loop-1.c   -O2  -DPREVENT_OPTIMIZATION  line 20 i == 1
FAIL: gcc.dg/guality/loop-1.c   -O2 -flto -fno-use-linker-plugin -flto-partition=none  -DPREVENT_OPTIMIZATION line 20 i == 1
FAIL: gcc.dg/guality/loop-1.c   -O2 -flto -fuse-linker-plugin -fno-fat-lto-objects  -DPREVENT_OPTIMIZATION line 20 i == 1
FAIL: gcc.dg/guality/loop-1.c   -O3 -g  -DPREVENT_OPTIMIZATION  line 20 i == 1

New passes: