1. Introduction

zolcgen is a transformation pass operating on SUIFrm assembly files, utilizing the SALTO (System for Assembly Language Transformation and Optimization) API.

The zolcgen SALTO pass produces the actual ZOLC initialization code that has to be inserted in a preceding basic block to the loop nest to update the ZOLC storage resources and is typically the first basic block of the targeted procedure.

This pass works for the SUIFrm instruction set and has been created for SALTO version 1.4.1beta3. Also, a SALTO distribution that has been modified (patched) in order to include support for the suifrm family backend should be used.

2. Technical information

The operation of zolcgen involves the following tasks:

1. conversion of LOOP pseudos to an LDSA-LDSI-LDSS-LDSF sequence of instructions (and their repositioning). The LDS[I|S|F] instructions are used for initializing loop bound (initial, final) and stride (step) values. An LDSA (Set index register alias) instruction associates the general- purpose register used for indexing of a certain loop with its loop address (loop_a). LDSA instructions can be used for static renaming in case of an architecture with dedicated loop index registers. For a homogeneous register architecture this information would be mapped on a small LUT providing the alias relation of registers used for indexing with their correspondent loop addresses.

2. the overhead instructions are properly handled and the respective overhead markers are removed. The "state" of an overhead marker can be one of the following:

   • KEEP (0): Do not alter the marked instruction. This is the default option.
   • REPLACE_NOP (1): Replace the marked instruction with a NOP (no operation).
   • REMOVE (2): Remove the marked instruction.

   In all cases, the overhead marker is removed as well.

3. the task entry and exit PC addresses are calculated and the corresponding LDS[N|X] instructions (Set a PC entry/exit address) are created.

More information on the LOOP and OVERHEAD instructions can be found in the README file of the tcfggen pass distribution.

3. Installation

• Install SALTO (assuming version 1.4.1beta3 and a working gcc/g++ 2.96 host compiler). You will need a modified SALTO supporting the suifvm architecture family.
• Unpack the zolcgen archive wherever you like.
• Add the path to the SALTO shared libs (typically this is: $SALTO_HOME/lib) to $LD_LIBRARY_PATH.
• Type make -f Makefile.suifvm to build the zolcgen pass.

With minimal work, the zolcgen could be added to the salto-1.4.1beta3 source code in order to be built along with the SALTO infrastructure according to the typical GNU configuration/build procedure:

If you are using a Linux Redhat 7.3 or 9.0 distribution, the following options will work:

If you are only interested in building the suifvm related libraries, the following can be used:

4. Usage details

The pass accepts an input file (*.s) in SUIFrm assembly form to operate. The output file is the transformed assembly file (*.zolc.s) which should be ready for simulation on a ZOLC-aware SUIFrm model e.g. written for ArchC.

Usage synopsys:

where options can be one (or more) of the following:

-disable-ldsa

Disable the translation of ldsa instructions.

-text-addr <value>

Set the base address (in bytes) of the .text segment (instruction memory) to <value>, written in decade form. The default value is 4096 (0x1000).

-proc <opt-unit>

Specify the name of the procedure to process with zolcgen.

Usage example:

5. Known limitations

1. ZOLC initialization instructions can only be appended to the first basic block of the procedure of interest.

6. Further information

[ArchC] The ArchC resource center. Available: http://www.archc.org

[Rohou96] E. Rohou, F. Bodin, A. Seznec, G. L. Fol, F. Charot, and F. Raimbault, SALTO: System for assembly-language transformation and optimization,. Institut National de Recherche en Informatique et en Automatique, Technical report 2980, September 1996.

[SALTO] The SALTO Project homepage. Available: http://www.irisa.fr/caps/projects/Salto/