clang loop weirdness

    .globl  tightloop
    .align  16, 0x90
    .type   tightloop,@function
tightloop:                              # @tightloop
    .cfi_startproc
# BB#0:
    xor eax, eax
    .align  16, 0x90
.LBB0_1:                                # =>This Inner Loop Header: Depth=1
    add qword ptr [rip + counter], rax
    inc rax
    cmp rax, 400000000
    jne .LBB0_1
# BB#2:
    ret
.Ltmp0:
    .size   tightloop, .Ltmp0-tightloop
    .cfi_endproc

    .globl  foo
    .align  16, 0x90
    .type   foo,@function
foo:                                    # @foo
    .cfi_startproc
# BB#0:
    ret
.Ltmp1:
    .size   foo, .Ltmp1-foo
    .cfi_endproc

    .globl  loop_with_extra_call
    .align  16, 0x90
    .type   loop_with_extra_call,@function
loop_with_extra_call:                   # @loop_with_extra_call
    .cfi_startproc
# BB#0:
    xor eax, eax
    .align  16, 0x90
.LBB2_1:                                # =>This Inner Loop Header: Depth=1
    #APP
    call foo
    #NO_APP
    add qword ptr [rip + counter], rax
    inc rax
    cmp rax, 400000000
    jne .LBB2_1
# BB#2:
    ret
.Ltmp2:
    .size   loop_with_extra_call, .Ltmp2-loop_with_extra_call
    .cfi_endproc