Introduction to Pentium Assembly Language

References: The following manuals may provide useful additional commentary for the elements of Pentium assembly langauge.

• Intel's Pentium III Manuals:
  These provide the definitive word on the Pentium and its instructions. While these are technically complete and good for reference, they may nor may not be easy reading for beginning assembly-language programmers.
  Note: The order of instructions operands for Intel assembly is reversed from the order used for AT&T Pentium Assembly -- as used by the gcc compiler and as assembler!
  • IA-32 Intel® Architecture Software Developer's Manual, Volume 1: Basic Architecture (pdf format: 4,005K bytes, 422 pages)
  • IA-32 Intel® Architecture Software Developer's Manual, Volume 2: Instruction Set Reference (pdf format: 6,593 Kbytes, 964 pages)
  • IA-32 Intel® Architecture Software Developer's Manual, Volume 3: System Programming Guide (pdf format: 6,269 Kbytes, 696 pages)
  • Intel® Pentium® 4 and Intel® Xeon^TM Processor Optimization (pdf format: 1,505 Kbytes, 333 pages)

  (These are large files, so will take some time to load. While one copy has been downloaded and is available locally through the above links, please do not make additional copies for own account.)

• Dominique Thiebau, The Art of Assembly Language Programming, http://cs.smith.edu/~thiebaut/ArtOfAssembly/ArtofAsm.html .
  
  This provides a nice description of the Pentium and its assembly language. Terminology follows general Intel conventions, but may not contain specific elements of GNU syntax.

• Dean Elsner, Jay Fenlason, and friends, Using as : The GNU Assembler, http://www.gnu.org/manual/gas-2.9.1/html_node/as_toc.html
  
  The basic assembler used on MathLAN's PC/Linux system.
  Note that the syntax for the as assembler may not follow normal Pentium conventions. The resulting code, however, is completely equivalent.

Steps for this Lab:

1. Programs ~walker/assembly/prog1.c and ~walker/assembly/prog2.c each contain a linear search procedure, written in C.

   1. Copy these programs to your account.
   2. Peruse, compile, and run the programs to check how they work.
   3. Compare on any similarities or differences between these two programs:
      • How are constants declared?
      • Where are variables item, elements and itemFound declared?
      • How are data values read?
      • What parameters are used for procedures, and what is being passed (e.g., addresses or values)?
      • How is the linear search performed?
      • How is the found variable set?

2. Compile prog1 to assembly code, using the command:

   
        gcc -S prog1.c
   

   This command will produce an assembly language program, stored in file prog1.s. Comment upon the general organization of data for the portion of this assembly language program which comes from the linearSearch procedure. In particular,
   1. Where are variables item, elements and itemFound stored?
   2. Indicate where the local variable index and the parameters number, dataArray and found are stored.
   3. Outline which registers are used for what information when.
   4. How are values computed for the done variable, and how is done tested in the code generated from the while and if statements.

3. Next compile prog2.c to assembly language.

   Annotate the portion of this assembly language program which comes from the linearSearch procedure. That is,

   1. Where are variables item, elements and itemFound declared?
   2. Indicate where all local variables and parameters are stored.
   3. Identify all assembly language instructions and macros in the listing.
   4. Outline which registers are used for what information when.

Work to be turned in:

• Commentary for step 1c.
• Steps 2a, 2b, 3a, and 3b may be accomplished either in a written discussion or with an appropriate diagram of memory.
• Steps 2c and 3d require a few sentences. While not required, a diagram of registers and their usage may expedite the discussion.
• Step 2d may be accomplished either in a written discussion or using a code listing which you annotate.
• Write the annotations for Step 3c on the assembled listing. The annotations may be either long hand or typed as comments.

This document is available on the World Wide Web as

     http://www.cs.grinnell.edu/~walker/courses/211.fa01/labs/as-assembler.html

created September 30, 1997 last revised October 8, 2001
For more information, please contact Henry M. Walker at walker@cs.grinnell.edu.