Exercise 1: Familiarizing yourself with Venus​

1. Open ex1.s into the Venus editor. If you were unable to mount the filesystem in Exercise 0, then you can copy/paste ex1.s from your local machine into the Venus editor directly.

2. Click the “Simulator” tab and click the “Assemble & Simulate from Editor” button. This will prepare the code you wrote for execution. If you click back to the “Editor” tab, your simulation will be reset.

3. In the simulator, to execute the next instruction, click the “step” button.

4. To undo an instruction, click the “prev” button. Note that undo may or may not undo operations performed by ecall, such as exiting the program or printing to console.

5. To run the program to completion, click the “run” button.

6. To reset the program from the start, click the “reset” button.

7. The contents of all 32 registers are on the right-hand side, and the console output is at the bottom.

8. To view the contents of memory, click the “Memory” tab on the right. You can navigate to different portions of your memory using the dropdown menu at the bottom.

Action Item​

1. What do the .data, .word, .text directives mean (i.e. what do you use them for)? Hint: think about the 4 sections of memory.
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.data means that the contents below are data; .word means that the following are bytes might be used; .text means that the following are instructions.

2. Run the program to completion. What number did the program output? What does this number represent?
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34. The 9th fib number;

3. At what address is n stored in memory? Hint: Look at the contents of the registers.
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0x10000010

4. Without actually editing the code (i.e. without going into the “Editor” tab), have the program calculate the 13th fib number (0-indexed) by manually modifying the value of a register. You may find it helpful to first step through the code. If you prefer to look at decimal values, change the “Display Settings” option at the bottom.
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• 通过观察，可以发现 n 的地址被 load 到了 t3 中；

• 然后，再根据 n 的地址，将其的值仍然存储到 t3 中；

• 那么我们直接将这个值改为13，也就是十六进制的D就可以。

Exercise 2: Translating from C to RISC-V​

Action Item​

• The register representing the variable k.
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t0 represents the variable k in C file;

• The register representing the variable sum.
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s0 represents the variable sum in C file;

• The registers acting as pointers to the source and dest arrays.
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s1 acting as the pointer to source array; s2 acting as the pointer to dest array;

• The assembly code for the loop found in the C code.
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• How the pointers are manipulated in the assembly code.
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By load the address of the array to some register, then access each item by adding an offset, or shift left logic or shift right logic;

Exercise 3: Factorial​

Testing​