[Bug tree-optimization/57430] New: Redundant move instruction is produced after function inlining

[ysrumyan at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57430

            Bug ID: 57430
           Summary: Redundant move instruction is produced after function
                    inlining
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ysrumyan at gmail dot com

This is based on performance analysis of eembc2.0 suite on Atom processor in
comparison with clang compiler.

I prepared a simple reproducer that exhibits the issue.

Hottest loop (from function "remove") consists of 7 instructions if inlining
was applied:
.L48:
    movl    %edx, %ebp   <<--  it is redundant!!
    movl    %ecx, %edx
.L39:
    cmpl    %edx, %eax
    je    .L24
    movl    16(%edx), %ecx
    testl    %ecx, %ecx
    jne    .L48

but without inlining it consists of 6 instructions:

.L5:
    cmpl    %eax, %ecx
    je    .L4
    movl    %eax, %edx
.L7:
    movl    16(%edx), %eax
    testl    %eax, %eax
    jne    .L5

In result we can see performance drop on 4% (Atom 32-bit mode).

The reproducer will be attached.