Big-Endian Structure Mapping and Mixed C & Assembly Programming
1. Objectives
In this lab you will learn
how to write structures that allocate memory efficiently. Also, you
will learn how to pass parameters between C and assembly code.
1.1 Reference
Files for Lab
2. Prelab
Before you come to lab it would be good to understand how to setup, declare, and use structures. Also, it would be good to understand EABI and how to pass parameters in mixed coding. You can find information on all of these topics in the following documents:
PowerPC Manual (Big-Endian Mapping is section 3.1.2.1, pages 3-2 to 3-4)
3. Big-Endian Structure Mapping
Observe the following structure.
When the struct is declared
as a variable type in main, memory is allocated for that declaration. Read
the Information about big endian mapping in the PowerPC manual. Recall that byte, half-word, word, and double
word alignment must be followed.
- Fill in the table on your answer sheet for the memory allocated by the struct. Assume big endian mapping, and use the hexadecimal values for each variable are given below.
- Now, rewrite the struct to use the memory space more efficiently. Write the new struct declaration and fill in the table for the new memory allocation. Use the same values for the variables.
4. Mixed C & Assembly Programming
Observe the following C & Assembly code.
- What
does the QTerm display after executing this code?