Whats a practical use for lea

[gygzkunw]

I know that lea is a shift-addition instruction and lets you load the address of an effective address. I also know it doesn't affect the flag register . But i still cant come up with a practical purpose for why i should use lea when i can use mov. Please i am assembly noob, try and keep it single.

[fredericopissarra]

1. You can use to do simple arithmetic calculations:

Code: [Select]

; int f( int x ) { return 5 * x; }
f:
  lea eax,[rdi+rdi*4]
  ret
2. You can use to precalculate a RIP relative address (x86-64):

Code: [Select]

  lea rax,[rel var]   ; You can get rid of 'rel' here if rip relative addressing is default.

3. You can get the address of an element in an array:

Code: [Select]

  ; Supose RCX is the index of an array of ints:
  lea rsi,[array+rcx*4]   ; rsi now points to array[rcx]


[Elawig57]

I just want to know about How is Lea used in the classroom? Optimum Mail

[fredericopissarra]

I just want to know about How is Lea used in the classroom?

And I gave you 3 uses...

[Frank Kotler]

LEA uses the classroom to teach itself to students so the students can use it outside of the classroom.

What's really on your mind, Elawig57?

Frank