What does the LEAL assembly instruction do?

LEA (load effective address) just computes the address of the operand, it does not actually dereference it. Most of the time, it’s just doing a calculation like a combined multiply-and-add for, say, array indexing.

In this case, it’s doing a simple numeric subtraction: leal -4(%ebp), %eax just assigns to the %eax register the value of %ebp - 4. It’s equivalent to a single sub instruction, except a sub requires the destination to be the same as one of the sources.

The movl instruction, in contrast, accesses the memory location at %ebp - 4 and stores that value into %eax.

Related Posts:

  1. What’s the purpose of the LEA instruction?
  2. Understanding cmp instruction
  3. What does the MOVZBL instruction do in IA-32 AT&T syntax?
  4. What’s the purpose of the LEA instruction?
  5. need help understanding the movzbl call in this function
  6. How to move ST(0) to EAX?
  7. The point of test %eax %eax
  8. Assembly: How does fld st(0) duplicates the top stack value in the following code?
  9. What does the MOVZBL instruction do in IA-32 AT&T syntax?
  10. What’s the purpose of the LEA instruction?
  11. The difference between cmpl and cmp
  12. x86 cmpl and jne
  13. What is the function of the push / pop instructions used on registers in x86 assembly?
  14. What is callq instruction?
  15. Display value found at given address gdb
  16. Purpose of ESI & EDI registers?
  17. What are the ESP and the EBP registers?
  18. IDIV operation in assembly (understanding)
  19. Convert C program into assembly code
  20. explanation about push ebp and pop ebp instruction in assembly
  21. x86 assembly: How does the ‘subl’ command work in AT&T syntax
  22. what does the cmpq instruction do?
  23. Purpose of ESI & EDI registers?
  24. xorl %eax – Instruction set architecture in IA-32
  25. Bubble sort on array on Assembly Language
  26. Nasm Error: invalid combination of opcode and operands
  27. When and why do we sign extend and use cdq with mul/div?
  28. How do AX, AH, AL map onto EAX?
  29. X86 assembly – Handling the IDIV instruction
  30. pop or add esp, 4 ? What is the difference?
  31. What is the difference between MOV and LEA?
  32. `testl` eax against eax?
  33. Difference between JE/JNE and JZ/JNZ
  34. Printing out a number in assembly language?
  35. What does `dword ptr` mean?
  36. Difference between JA and JG in assembly
  37. what does the the dword operand do in assembly
  38. [Binary Bomb – Phase 4
  39. assembly “mov” instruction
  40. Why shift a bit using sll and such in MIPs Assembly?
  41. Assembly code vs Machine code vs Object code?
  42. Understanding how `lw` and `sw` actually work in a MIPS program
  43. ARM Assembler – How do I use CMP, BLT and BGT?
  44. MIPS: lw (load word) instruction
  45. What is the meaning of XOR in x86 assembly?
  46. What does the BEQ instruction do exactly?
  47. What’s the size of a QWORD on a 64-bit machine?
  48. MIPS assembly for a simple for loop
  49. Difference between JA and JG in assembly
  50. mips .word function and differences between 2 codes
  51. Why doesn’t there exists a subi opcode for MIPS?
  52. LC3 LEA instruction and the value stored
  53. What exactly does the lb instruction do?
  54. lc3 LDR instruction and the value stored
  55. What is the difference between la and li in opcodes in MIPS?
  56. What does movslq do?
  57. Assembly language je jump function
  58. What are .S files?
  59. Why are rbp and rsp called general purpose registers?
  60. x86 Assembly pointers
  61. what is the use of ori in this part of MIPS code?
  62. Storing a user’s input in MIPS
  63. Integer absolute value in MIPS?
  64. MIPS Assembly – lui $t0, 4097?
  65. Difference between “move” and “li” in MIPS assembly language
  66. Greater than, less than equal, greater than equal in MIPS
  67. Assembly addq clarification
  68. Which variable size to use (db, dw, dd) with x86 assembly?
  69. Assembly x86 – “leave” Instruction
  70. MIPS program jr $ra instructions and stack handling
  71. How can one see content of stack with GDB?
  72. Assembly – JG/JNLE/JL/JNGE after CMP
  73. Subtract two input numbers
  74. writing functions in assembler
  75. JNZ & CMP Assembly Instructions
  76. Assembly language (MIPS) difference betweent addi and add
  77. MIPS Address out of range (MARS)
  78. How do I compile the asm generated by GCC?
  79. Difference between “addi” and “add” for pseudoinstruction “move” in MIPS?
  80. sorting array in mips (assembly)
  81. what is a file handle and where it is useful for a programmer?
  82. How does `Skipcond` work in the MARIE assembly language?
  83. What are callee and caller saved registers?
  84. Multiplication by a power of 2 using Logical shifts in MIPS assembly
  85. MIPS instruction and machine code
  86. Convert from Java to MIPS
  87. Understanding Assembly MIPS .ALIGN and Memory Addressing
  88. error A2022: instruction operands must be the same size
  89. What’s the difference between a word and byte?
  90. Assembly Language – How to do Modulo?
  91. MIPS to C Translation
  92. Difference between movq and movabsq in x86-64
  93. GDB no such file or directory
  94. What is the jmpq command doing in this example
  95. Assembly – JZ instruction after CMP
  96. What does bx lr do in ARM assembly language?
  97. `js` and `jb` instructions in assembly
  98. (.text+0x20): undefined reference to `main’ and undefined reference to function
  99. Why am I getting this error: “data definition has no type or storage class”?
  100. Why are there no hashtables in the C standard library?

Leave a Comment

deneme bonusudeneme bonusu veren sitelerOnwin Güncel Giriştürkçe altyazılı pornocanlı bahis casino