[Bug tree-optimization/70771] [7 Regression] ICE on valid code at -O3 on x86_64-linux-gnu in operator[], at vec.h:714

[amker at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70771

--- Comment #2 from amker at gcc dot gnu.org ---
Also like PR70775, this case failed the change allows single argument PHIs in
if-cvt now.  It looks like there is something wrong when handling single
argument PHIs.  Before the change, we simple return false in
ifcvt_convertible_phi_p and skip if-conversion for such form loops.