Regressions on trunk at revision 262513 vs revision 262510

[H.J. Lu ia32 Core i7]

New failures:
FAIL: gcc.dg/pr84100.c  (test for warnings, line 11)

New passes:
FAIL: gcc.dg/guality/pr48437.c   -O2 -flto -fno-use-linker-plugin -flto-partition=none  -DPREVENT_OPTIMIZATION line 14 i == 0
FAIL: gcc.dg/guality/pr48437.c   -O2 -flto -fuse-linker-plugin -fno-fat-lto-objects  -DPREVENT_OPTIMIZATION line 14 i == 0