Lect 6: Instruction Set

1
Lect 6 Instruction Set
2
Instruction Set

• Logic Instructions
• AND, OR, XOR, NOT
• Shift Instructions
• SAL/SHL, SHR/SAR, SHLD, SHRD
• SHL AX, 1 SAR AX, CL
• Rotate Instructions
• ROL, ROR, RCL, RCR
• ROR AX,1 ROL AX, CL
• Bit Test and Bit Scan Instructions
• BT(Bit Test), BTR(Bit test and reset), BTS(Bit
  test and set), BTC(Bit test and complement),
  BSF(Bit scan forward), BSR(Bit scan reverse)
• BT D, S CF BITD,S saves the value of the
  bit indicated by the first operand and the bit
  offset into the CF flag
• BSF r16,r/m16 or BSF r32, r/m32
• scans the bits in the second word or double
  word operand starting with bit 0. The ZF flag is
  set if all the bits are 0 otherwise, the ZF flag
  is cleared and the destination register is loaded
  with the bit index of the first set bit.

3
Instruction Set

• Flag-Control Instructions
• LAHF(Load AH from flags), SAHF(Store AH into
  flags), CLC, STC, CMC, CLI, STI
• AH SFZF - AF - PF - CF
• Compare and Set Instructions
• CMP
• SETcc r/m8 if condition then r/m8 1(not FF)
  else r/m8 0
• SETA, SETAE,.....
• Jump Instructions
• Unconditional(JMP) and Conditional Jumps(JA, JAE,
  .... )
• JMP Intrasegment jump, Intersegment jump
• Intrasegment jump short(8-bit displacement
  -126 to 129), direct within segment (16-bit or
  32-bit relative), r/m indirect with segment
• Intersegment jump direct intersegment (full
  offset and selector), indirect intersegment
• Jcc conditional jump 8-bit or full
  displacement
• JA, JAE, ....

4
Instruction Set

• Subroutines and Subroutine-Handling Instructions
• CALL and Return Instructions
• CALL intrasegment and intersegment call
• Intrasegment CALL rel16, or rel32, CALL
  indirect within segment
• Intersegment CALL direct intersegment, CALL
  indirect intersegment
• RET
• Intrasegment RET within segment, RET within
  segment Adding Immediate to SP
• Intersegment RET, RET adding immediate to SP
• Stack Frame Instructions ENTER and LEAVE
• to allocate and deallocate a data area called a
  stack frame
• ENTER make a stack frame
• ENTER imm16,0 Make procedure stack frame
• ENTER imm16,1 Make stack frame for procedure
  parameter
• ENTER imm16,imm8 Make stack frame for procedure
  parameter
• first operand the number of bytes to be
  allocated on the stack for local data storage
• second operand lexical nesting level of the
  routine

5
Instruction Set
Data for Proc. C (16 bytes) BP for Proc. C BP
for Proc. B BP for Proc. A BP for Proc. B Ret
addr for proc. B Data for Proc. B (12 bytes) BP
for Proc. B BP for Proc. A BP for Proc. A Ret
addr for proc. A Data for Proc. A (32 bytes) BP
for Proc. A Old BP
Stack frame for C
BP when executing Procedure C
Stack frame for B
BP when executing Procedure B
Stack frame for A
BP when executing Procedure A
6
Instruction Set

• Loop and Loop-handling Instructions
• LOOP, LOOPE/Z, LOOPNE/NZ CX must be preloaded
  with a count
• String and String-Handling Instructions
• MOVSB/W/D, compare string, scan string, load
  string, store string
• the contents of both SI and DI are automatically
  incremented or decremented.
• REP repeat string
• Check Array Index Against Bounds
• BOUND r16, m1616 check if r16 is within bounds
• BOUND r32, m32m32 check if r32 is within bounds
• operation if (LeftSRC lt RightSRC or LeftSRCgt
  RightSRCOperandSize/8)
• then Interrupt 5