[Bug rtl-optimization/55190] ivopts causes loop setup bloat

["amodra at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55190

Alan Modra <amodra at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|sh*-*-* arm*-*-*            |sh*-*-* arm*-*-*
                   |                            |powerpc*-*-*
                 CC|                            |amodra at gmail dot com

--- Comment #10 from Alan Modra <amodra at gmail dot com> ---
Seen also on powerpc.  Even for simple testcases like
int b[30];
void
fn1 (unsigned int n)
{
  unsigned int i;
  for (i = 0; i < n; i++)
    b[i] = 42;
}

I see for -m32
fn1:
        cmpwi 0,3,0
        beq 0,.L1
        slwi 9,3,2      ####
        lis 10,b-4@ha
        addi 9,9,-4     ####
        la 10,b-4@l(10)
        srwi 9,9,2      ####
        li 8,42
        addi 9,9,1      ####
        mtctr 9
        .p2align 4,,15
.L3:
        stwu 8,4(10)
        bdnz .L3
.L1:
        blr
All of the insns marked #### are redundant.

For -m64 this loop doesn't even use bdnz
Loop 1 is simple:
  simple exit 4 -> 5
  infinite if: (expr_list:REG_DEP_TRUE (ne:SI (and:DI (plus:DI (minus:DI
(ashift:DI (reg:DI 189)
                        (const_int 2 [0x2]))
                    (reg:DI 179 [ ivtmp.7 ]))
                (symbol_ref:DI ("b") [flags 0x80]  <var_decl 0x7fe7521de870
b>))
            (const_int 3 [0x3]))
        (const_int 0 [0]))
    (nil))
  number of iterations: (lshiftrt:DI (plus:DI (minus:DI (reg:DI 185 [ _18 ])
            (reg:DI 179 [ ivtmp.7 ]))
        (const_int -4 [0xfffffffffffffffc]))
    (const_int 2 [0x2]))
  upper bound: 29
  likely upper bound: 29
  realistic bound: -1
Doloop: Possible infinite iteration case.
Doloop: The loop is not suitable.