NAME¶

copt - peephole optimizer

SYSNOPIS¶

copt file ...

DESCRIPTION¶

copt is a general-purpose peephole optimizer. It reads code from its standard input and writes an improved version to its standard output. copy reads the named files for its optimizations, which are encoded as follows:

          <pattern for input line 1>
          <pattern for input line 2>
           ...
          <pattern for input line n>
          =
          <pattern for output line 1>
          <pattern for output line 2>
           ...
          <pattern for output line m>
          <blank line>

Pattern matching uses literal string comparison, with one exception: ``%%'' matches the ``%'' character, and ``%'' followed by a digit matches everything up to the next occurrence of the next pattern character, though all occurrences of % n must denote the same string. For example, the pattern ``%1=%1.'' matches exactly those strings that begin with a string X, followed by a ``='' (the first), followed by a second occurrence of X, followed by a period. In this way, the input/output pattern

          mov $%1,r%2
          mov *r%2,r%2
          =
          mov %1,r%2

commands copt to replace runs like

          mov $_a,r3
          mov *r3,r3

with

          mov _a,r3

Note that a tab or newline can terminate a % n variable. copt compares each run of input patterns with the current input instruction and its predecessors. If no match is found, it advances to the next input instruction and tries again. Otherwise, it replaces the input instructions with the corresponding output patterns, pattern variables instantiated,and resumes its search with the first instruction of the replacement. copt matches input patterns in reverse order to cascade optimizations without backing up.

BUGS¶

Errors in optimization files are always possible.

SEE ALSO¶

z88dk(1), z88dk-zcc(1), z88dk-z80asm(1), z88dk-appmake(1), z88dk-copt(1).

AUTHOR¶

z88dk was written by Dominic Morris <dom@z88dk.org>, and others.