Assembly Language Instructions Quiz

Data Movement Instructions

• The 'movl' instruction exhibits exceptional behavior when a register is used as the destination, as it zero-extends the register to 64 bits.
• In x86-64, instructions that produce a 32-bit value for a register follow the convention of zero-extending the result to 64 bits.

'movabsq' Instruction

• The 'movabsq' instruction is used to handle immediate data, allowing for 64-bit immediate values to be moved into a register.

'movq' Instruction

• The regular 'movq' instruction can accept various source operands, including registers, memory locations, and immediate values.

Data Movement Instructions (Figures 3.5 and 3.6)

• Figures 3.5 and 3.6 document the different types of data movement instructions, including mov, movz, and movs.

'mov' Instruction Convention

• The 'mov' instruction convention dictates that the source operand comes first, followed by the destination operand.

Assembly Code Analysis

• In the provided assembly code, the argument rp is saved in a different register (line 2) to preserve the original value.
• The register %rax is used to hold the quotient after the division operation.
• The assembly code performs a signed division operation.
• The 'cqo' instruction is used to sign-extend the dividend in the provided assembly code.
• Lines 1 and 8 of the assembly code respectively accomplish setting up the dividend and storing the result.
• Before performing an unsigned division, %rdx should be set to 0.

Operand Types

• A register operand denotes the contents of a register.
• A memory reference operand consists of a base register, index register, scale factor, and displacement.
• An address operand is used to reference a value stored in memory starting at a specific address.
• A scaled indexed address is often used when addressing elements of arrays.
• The effective address in a general memory reference is computed as: address = base + index * scale + displacement.

Sign-Extension and Zero-Extension

• The 'movs' instruction sign-extends the source operand to the destination register.
• The 'movz' instruction zero-extends the source operand to the destination register.
• The 'movsbq' instruction sign-extends the 8-bit source operand to the 64-bit destination register.

Conditional Moves

• Using conditional moves in code execution achieves faster performance and reduces branching.
• In the context of code execution, 'TMP' represents a temporary value.
• 'TOK' and 'Tran' are related in the context of code execution, where TOK is the threshold and Tran is the transition time.
• Code compiled using conditional moves takes around 8 clock cycles regardless of the data being tested because the branch predictor is not affected.
• When the branching pattern is random, the code requires around 45 cycles, indicating poor branch prediction.
• The approximate miss penalty can be calculated as TOK + Tran = 8 + 17.5 = 25.5.

Test your knowledge of assembly language instructions by determining the appropriate instruction suffix based on the operands provided in each line of assembly language code. This quiz includes practice problems similar to the given example.