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DDCA Ch6 - Part 9: RISC-V Conditional Statements
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DDCA Ch6 - Part 9: RISC-V Conditional Statements

Translating Conditional Statements and Loops to Assembly Language

In this section, the video discusses the translation of conditional statements and loops from high-level languages like C into assembly language. It covers the conversion process for if statements, if-else statements, while loops, and for loops.

Translating If Statements

  • When translating an if statement from C to assembly language:
  • Compare variables i and j stored in registers.
  • Branch on not equal to skip the body if i is not equal to j.
  • Perform operations based on equality or inequality conditions.
  • Handling false conditions in an if statement:
  • Branch to a location after the if statement.
  • Execute the body of the if statement.
  • Continue with code execution post-if statement.

Translating If-Else Statements

  • Translation process for if-else statements:
  • Start with a branch on not equal condition.
  • Differentiate actions based on equality or inequality of variables.

Understanding Loops

  • Exploring loop translation:
  • Example scenario: Computing powers of x until reaching a specific value (2^x = 128).
  • Iterative doubling approach to find the power efficiently.
  • Implementing a while loop:
  • Comparing values within registers using branches.
  • Executing loop body based on condition satisfaction.

Implementing For Loops

  • Converting for loops to assembly language:
  • Initialization, condition check, body execution, and iteration update steps.
  • Example: Summing numbers from zero to nine using a for loop:
  • Initializing variables for sum and iteration count.

Adding Powers of 2 Using For Loop

In this section, the speaker demonstrates using a for loop to add the powers of 2 from 1 to 100 in RISC-V assembly language.

Initializing and Setting Up the Loop

  • Initialize sum to zero.
  • Start i at 1 and set the comparison limit to 101.

Implementing the For Loop

  • Check if i is less than 101 to enter the loop body.
  • Update sum by adding i each iteration.
  • Perform post-operation: i = i * 2 using a left shift operation.

Alternative Instruction in RISC-V Assembly

  • Introduce the "set less than" instruction for comparing two numbers.
  • Demonstrate setting a temporary register based on whether i is less than 101.
  • Use branch instructions based on the result of the comparison.