[Bug rtl-optimization/44374] New: Hoist same instructions in different branches

[carrot at google dot com]

Compile the attached test case with options -march=armv7-a -mthumb -Os, 
this code snippet 

  if (native)
    dlmalloc_walk_heap(heap_chunk_callback, (void *)&ctx);
  else
    dvmHeapSourceWalk(heap_chunk_callback, (void *)&ctx);

is compiled to:

        cbz     r5, .L2
        ldr     r0, .L4            // A
        mov     r1, sp             // B
        bl      dlmalloc_walk_heap
        b       .L1
.L2:
        ldr     r0, .L4            // C
        mov     r1, sp             // D
        bl      dvmHeapSourceWalk
.L1:
        add     sp, sp, #44
        pop     {r4, r5, pc}
.L5:
        .align  2
.L4:
        .word   heap_chunk_callback

Note that instructions AB are equal to instructions CD, if we move the previous
conditional branch after B, then CD can be removed.

Option -O2 and target arm have the same problem.

Which pass should do this optimization? pass_rtl_hoist?


-- 
           Summary: Hoist same instructions in different branches
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: carrot at google dot com
 GCC build triplet: i686-linux
  GCC host triplet: i686-linux
GCC target triplet: arm-eabi


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44374