C51: Command Line Global Register Optimization

Information in this article applies to:

• C51 Version 5 and Later

QUESTION

How is the REGFILE directive used on the command line to achieve global register optimization? The manual does not seem to describe this in detail.

ANSWER

1. Compile your source file and invoke the linker with the REGFILE directive. For example:

   BL51 FOO.OBJ, BAR.OBJ TO FOOBAR PRINT(FOOBAR.M51) REGFILE(FOOBAR.REG)
   

2. Look at the end of the linker map file (.m51). If you see something like the following, then you must rebuild your project as described in steps 3 and 4:

   RE-TRANSLATION LIST FOR OPTIMAL REGISTER MASKS
   
   
   MESSAGE                         MODULE
      INFORMATION
   --------------------------------------
   
   ** RE-TRANSLATION SUGGESTED **  FOO.OBJ (FOO)
      REG MASK (@000000) IS TOO PESSIMISTIC FOR FUNCTION '_TOUPPER'
   

3. Recompile the source files required, using the compiler REGFILE directive. In the example above, FOO.C compiles to produce FOO.OBJ, so only FOO.C needs to be recompiled. When using the directive, specify the .REG file generated by the linker in step 2.

   C51 FOO.C REGFILE(FOOBAR.REG)
   

4. Relink and repeat step 2 until retranslation is no longer suggested.

MORE INFORMATION

• Refer to REGFILE in the BL51 User's Guide.
• Refer to REGFILE in the Cx51 User's Guide.

SEE ALSO

• C51: REGFILE Directive

Last Reviewed: Thursday, February 25, 2021