[Bug target/46551] Generate complex addressing mode CMP instruction in x86-64

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=46551

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |missed-optimization
         Resolution|---                         |FIXED
      Known to fail|                            |4.9.0, 5.1.0
             Status|UNCONFIRMED                 |RESOLVED
      Known to work|                            |6.1.0

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
GCC 6+ produces:
        movq    (%rsi), %rcx
        movq    %rdi, %rax
        cmpq    %rdx, (%rsi,%rcx,8)
        je      .L2


The difference comes from expand.
GCC 6 produces:
(insn 9 8 10 2 (set (reg:CCZ 17 flags)
        (compare:CCZ (mem:DI (plus:DI (mult:DI (reg:DI 101)
                        (const_int 8 [0x8]))
                    (reg/v/f:DI 99 [ vm ])) [1 vm_3(D)->cell S8 A64])
            (reg/v:DI 100 [ a ]))) /app/example.cpp:12 -1
     (nil))

While GCC 5 produces:
(insn 9 8 10 2 (set (reg:DI 89 [ D.1961 ])
        (mem:DI (plus:DI (mult:DI (reg:DI 101)
                    (const_int 8 [0x8]))
                (reg/v/f:DI 99 [ vm ])) [1 vm_3(D)->cell S8 A64]))
/app/example.cpp:12 -1
     (nil))
(insn 10 9 11 2 (set (reg:CCZ 17 flags)
        (compare:CCZ (reg:DI 89 [ D.1961 ])
            (reg/v:DI 100 [ a ]))) /app/example.cpp:12 -1
     (nil))


I can't find the change that caused this difference though.