Regressions on trunk at revision 272234 vs revision 272181

[H.J. Lu (ia32 Core i7)]

New failures:
FAIL: g++.dg/tree-ssa/pr31146.C  -std=gnu++14  scan-tree-dump forwprop1 "MEM\\[.*&i\\]\\[j.*\\] =.* 1;"
FAIL: g++.dg/tree-ssa/pr31146.C  -std=gnu++17  scan-tree-dump forwprop1 "MEM\\[.*&i\\]\\[j.*\\] =.* 1;"
FAIL: g++.dg/tree-ssa/pr31146.C  -std=gnu++98  scan-tree-dump forwprop1 "MEM\\[.*&i\\]\\[j.*\\] =.* 1;"
FAIL: g++.dg/tree-ssa/ssa-dse-1.C   scan-tree-dump-times dse1 "MEM <char\\[176]> \\[\\(struct FixBuf \\*\\)&<retval> \\+ [0-9]+B\\] = {}" 1

New passes: