Compiler doesn't implement "Conditional Execution Instruction" (e.g. SUBS). Why ?

Hello,

In the excellent textbook ARM System Developer's Guide: Designing and Optimizing System Software (Andrew N. Sloss, Dominic Symes, Chris Wright - Elsevier, 2004) there is example on the page 115:

int checksum_v6(int *data)
{
unsigned int i;
int sum=0;
for (i=64; i!=0; i--)
{
sum += *(data++);
}
return sum;
}

that is disassembled (according to authors) in the following code:

checksum_v6

     MOV r2,r0 ; r2 = data

     MOV r0,#0 ; sum = 0

     MOV r1,#0x40 ; i = 64

checksum_v6_loop

     LDR r3,[r2],#4 ; r3 = *(data++)

     SUBS r1,r1,#1 ; i-- and set flags

     ADD r0,r3,r0 ; sum += r3

     BNE checksum_v6_loop ; if (i!=0) goto loop

     MOV pc,r14 ; return sum

I reproduced this example, and what I've got this:

checksum_v6 PROC

        MOV      r2,r0

        MOV      r0,#0

        MOV      r1,#0x40

|L1.48|

        LDR      r3,[r2],#4

        ADD      r0,r0,r3

        SUB      r1,r1,#1

        CMP      r1,#0

        BNE      |L1.48|

        BX       lr

        ENDP

As you can state (highlighted in red) in my version of disassembly instead of one conditional execution instruction (that is more efficient) compiler placed 2 instructions: SUB and CMP.

I've tried with all optimization options but couldn't reproduce book authors disassembly.

Does exist some flag that regulates such kind of things ?

Thanks in advance.

Pavel