1. The Assembly Language Level
Chapter 7

2. Assembly Language
True assembly is a one to one mapping with machine language instructions
Assembly language translated into object program or executable binary program
When running program, 3 levels are present,
microarchitecture
ISA
OSM

3. Reasons for Assembly Pro –Faster Pro - Smaller
Pro- Full access to hardware
interrupts
device controllers
Con- takes longer to write
Con – takes longer to debug
Con – Harder to maintain
Con – Limited to single family architecture

4. Why Use Assembly Language?
Comparison of assembly language and high-level language
programming, with and without tuning.

5. Assembly Optimize code Writing for machine with limited resources
Tuning – recoding in assembly to speed critical code sections
Understand how compilers work and what they produce
Only way to get feel of ISA level

6. Format of an Assembly Language Statement (1)
Computation of N = I + J. (a) Pentium 4.

7. Format of an Assembly Language Statement (2)
Computation of N = I + J. (b) Motorola 680x0.

8. Format of an Assembly Language Statement (3)
Computation of N = I + J. (c) SPARC.

9. Pseudoinstructions (1)
Some of the pseudoinstructions available in the
Pentium 4 assembler (MASM).

10. Pseudoinstructions (2)
Some of the pseudoinstructions available in the
Pentium 4 assembler (MASM).

11. Macro Definition, Call, Expansion (1)
Assembly language code for interchanging P and Q twice.
(a) Without a macro (b) With a macro.

12. Macro Definition, Call, Expansion (2)
Comparison of macro calls with procedure calls.

13. Macros with Parameters
Nearly identical sequences of statements.
(a) Without a macro. (b) With a macro.

14. The instruction location counter (ILC) keeps track of the address
Two Pass Assemblers (1)
The instruction location counter (ILC) keeps track of the address
where the instructions will be loaded in memory. In this example, the statements prior to MARIA occupy 100 bytes.

15. A symbol table for the program of Fig. 7-7.
Two Pass Assemblers (2)
A symbol table for the program of Fig. 7-7.

16. A few excerpts from the opcode table for a Pentium 4 assembler.
Two Pass Assemblers (3)
A few excerpts from the opcode table for a Pentium 4 assembler.

17. Pass one of a simple assembler.
. . .
Pass one of a simple assembler.

18. Pass one of a simple assembler.
. . .
. . .
Pass one of a simple assembler.

19. Pass one of a simple assembler.
. . .
Pass one of a simple assembler.

20. Pass two of a simple assembler.
. . .
Pass two of a simple assembler.

21. Pass two of a simple assembler.
. . .
Pass two of a simple assembler.

22. The Symbol Table (1)
Hash coding. (a) Symbols, values, and the hash codes derived from the symbols.

23. The Symbol Table (2)
Hash coding. (b) Eight-entry hash table with linked lists of symbols and values.

24. Linking and Loading
Generation of an executable binary program from a collection of
independently translated source procedures requires using a linker.

25. Tasks Performed by the Linker (1)
Each module has its own address space, starting at 0.

26. Tasks Performed by the Linker (2)
Each module has its own address space, starting at 0.

27. Tasks Performed by the Linker (3)
Each module has its own address space, starting at 0.

28. Tasks Performed by the Linker (4)
Each module has its own address space, starting at 0.

29. Tasks Performed by the Linker (5)
The object modules of Fig after being positioned in the binary image but before being relocated and linked.

30. Tasks Performed by the Linker (6)
The same object modules after linking and after relocation has been performed. Together they form an executable binary program, ready to run

31. Structure of an Object Module
The internal structure of an object module produced by a translator.

32. Binding Time and Dynamic Relocation
The relocated binary program of Fig. 7-15(b) moved up 300 addresses. Many instructions now refer to an incorrect memory address.

33. Dynamic Linking in MULTICS (1)
Before EARTH is called.

34. Dynamic Linking in MULTICS (2)
After EARTH has been called and linked.

35. Dynamic Linking in Windows
Use of a DLL file by two processes.