Simple assembly loop [beginner] - where are the conditions and why register value is automatically decreasing

Question

I'm taking my first steps into assembly x86 on Windows.

My question is why does ecx decrease with each loop, and why does the program know when to break the loop?

I'm posting the code, debugger output and some comments

Code:

.386    
.model  flat

.data
intArray DWORD  1h,2h,3h,4h;

.code
start proc 
    mov edi,OFFSET intArray
    mov ecx,LENGTHOF intArray
    mov eax,0

LP: 
    add eax,[edi]
    add edi,TYPE intArray
    loop LP 
    ret

start endp 
end 

In the debugger I can see that with each loop the value of ecx decreases by one:

LP 0:
    ecx = 4
LP 1:
    ecx = 3
LP 2:
    ecx = 2
LP 3:
    ecx = 1
LP 4:
    ecx = 0

At the begining mov ecx,LENGTHOF intArray it's moving 4 to ecx.

According to the docs

LENGTHOF
Returns the number of data objects in variable.

• https://learn.microsoft.com/en-us/cpp/assembler/masm/operator-lengthof?view=msvc-170 it should simply move value 4 into ecx, there is no information about tracking the intArray and updating it in runtime, so why it is decreasing?

If I understand the code correctly, it should work like this:

#include <iostream>

using namespace std;

int main()
{
    int intArray[4] = { 1, 2, 3, 4 };
    
    int *edi = intArray;
    int ecx = sizeof(intArray) / sizeof(int);
    int eax = 0;
    
    for(int i = 0; i < 4; i++) { 
        eax += *edi;
        ecx -= 1;
        edi = (int*)(((intptr_t)edi) + sizeof(int));
    }
    
    return 0;
}

but in assembly language the for loop condition and ecx decrementation are missing (I don't know where to look for it).

Is it hidden in flags?

Maybe someone could recommend a source that explains this problem?

Thank you!

Registers output

1. stopped at the line add edi,TYPE intArray

EAX = 00000001 EBX = 01028000 ECX = 00000004 EDX = 00A71005 ESI = 00A71005 EDI = 00A74000 EIP = 00A71021 ESP = 012FFDAC EBP = 012FFDB8 EFL = 00000202 

OV = 0 UP = 0 EI = 1 PL = 0 ZR = 0 AC = 0 PE = 0 CY = 0 

2. stopped at the line add edi,TYPE intArray

EAX = 00000003 EBX = 01028000 ECX = 00000003 EDX = 00A71005 ESI = 00A71005 EDI = 00A74004 EIP = 00A71021 ESP = 012FFDAC EBP = 012FFDB8 EFL = 00000206 

OV = 0 UP = 0 EI = 1 PL = 0 ZR = 0 AC = 0 PE = 1 CY = 0 

3. stopped at the line add edi,TYPE intArray

EAX = 00000006 EBX = 01028000 ECX = 00000002 EDX = 00A71005 ESI = 00A71005 EDI = 00A74008 EIP = 00A71021 ESP = 012FFDAC EBP = 012FFDB8 EFL = 00000206 

OV = 0 UP = 0 EI = 1 PL = 0 ZR = 0 AC = 0 PE = 1 CY = 0 

4. stopped at the line add edi,TYPE intArray

EAX = 0000000A EBX = 01028000 ECX = 00000001 EDX = 00A71005 ESI = 00A71005 EDI = 00A7400C EIP = 00A71021 ESP = 012FFDAC EBP = 012FFDB8 EFL = 00000206 

OV = 0 UP = 0 EI = 1 PL = 0 ZR = 0 AC = 0 PE = 1 CY = 0 

5. stopped at the line ret

EAX = 0000000A EBX = 01028000 ECX = 00000000 EDX = 00A71005 ESI = 00A71005 EDI = 00A74010 EIP = 00A71026 ESP = 012FFDAC EBP = 012FFDB8 EFL = 00000212 

OV = 0 UP = 0 EI = 1 PL = 0 ZR = 0 AC = 1 PE = 0 CY = 0