uopt(1)
uopt - MIPS ucode global optimizer
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NAME uopt - MIPS ucode global optimizer SYNOPSIS uopt unopt_file opt_file [string_file] [-t sym_file] [-i ignore_file] [-l list_file] [-Olimit count] [-loopunroll count] [-v] [-w] [-bb] [- O3] [-EL] [-EB] [-doassoc] [-f77alias] [-pic2] [-nokpicopt] [-kpicopt] [-no_r23] [-nomultibbunroll] [-zdbug:n] DESCRIPTION uopt, the MIPS ucode optimizer, reads the input binary ucode file, performs optimization on an intra-procedural, global basis and outputs the optimized binary ucode file. It checks the version stamp of the ucode file, and if it does not correspond to its own stamp, a warning message will be issued. By convention, unoptimized binary ucode files have the extension .B and optimized binary ucode files have the extension .O, but uopt does not force this convention on the user. The string file is used for storing string and floating-point constants in each procedure during optimization, to save memory space. If this file name is omitted, the file name uoptstring is used. uopt first conducts a quick pre-pass over the entire program. In the main optimization pass, it reads, optimizes and writes out the procedures one by one in the same order that they appear in the input file. The complexity of global optimization is some exponential function of the size of the procedure (in number of basic blocks). Thus, large procedures take enormous amount of time to optimize. Also, if the host machine has only a small amount of memory, excessive swapping of memory pages between disk physical memory further lengthens the optimization time for large procedures. uopt will skip optimizing a procedure if the number of basic blocks it contains exceeds 500. A warning message if issued so that the user is aware that the procedure is not optimized. The default value of 500 can be overridden using the -Olimit option. The following options are accepted by uopt: -v Turns on verbose mode. In this mode, uopt will print the name of the procedure it is currently optimizing, plus a number enclosed in parentheses that tells the number of basic blocks in that procedure. Optimization time is usually some exponential function of the number of basic blocks in the procedure. Under -O3 optimization, an i after the number indicates that inter-procedural register allocation is performed for that procedure. -w Suppresses warning messages. -bb Writes out the basic block number as ucode comments in the output ucode. This is useful in debugging uopt. -O3 Uses the inter-procedural technique when performing register allocation. -EL Tells uopt that the target machine is little-endian. -EB Tells uopt that the target machine is big-endian. -doassoc Performs the re-association optimization for floating- point expressions even when the language is FORTRAN. This violates the FORTRAN Standard. -f77alias Assumes that there can be aliasing among the parameters to a procedure when the language is FORTRAN. The FORTRAN Standard allows the assumption by compilers that there is never any aliasing among parameters. This assumption allows the compiler to get better performance for the program. If a program violates this rule, the program may not run correctly after default optimization; using this flag will still allow the program to run correctly after optimization, but at a reduced performance level. -pic2 Tells uopt that the program is being compiled for execution with dynamic shared objects. -nokpicopt Asks uopt to not perform the special treatment for global variables to optimize their program accesses under shared compilation. -kpicopt Asks uopt to perform the special treatment for global variables to optimize their program accesses regardless of the shared/non-shared compilation mode. -no_r23 Tells uopt that it should not use register 23. -nomultibbunroll Disables unrolling for loops containing branches. -zdbug:n Tells uopt to print different debugging traces, depending on the value of n. Traces are printed on a per-procedure basis, and output to the list file specified in the -l option. The traces always begin with the control flow graph of the procedure. For value 1, the local hash table and the global hash table are printed. For value 2, the local hash table, the global hash table are printed; the bit vectors for the local attributes are then printed on a per-basic-block basis. For value 3, the global hash table is printed, followed by the bit vectors for the partial redundancy data flow analysis. For value 4, the global hash table is printed, followed by the bit vectors to determine the live ranges of global common subexpressions. For value 5, the global hash table is printed, followed by the live range information for all the register-residing candidates, followed by the bit vectors related to register allocation. For value 6, a trace of the global register allocation via priority-based coloring is printed. For value 7, the inter-procedural register allocation information is printed. -t sym_file Tells uopt the name of the symbol table file. -i ignore_file Tells uopt to ignore specific procedures and leave them unoptimized. The procedures whose optimization is to be suppressed are listed in arbitrary order in the given file, with each line containing one procedure name starting at the first column. -l list_file Uses list_file to print diagnostic information during optimization. -Olimit count Sets this parameter to the value count. uopt will not optimize a procedure whose size in terms of number of basic blocks exceeds this value. -loopunroll count Sets the maximum number of times that a loop will be unrolled. The default value is 4. Setting it to 0 or 1 will disable loop unrolling. DIAGNOSTICS uopt assumes the input ucode file is error-free. However, it does issue warning messages when it runs into special situations during optimization. SEE ALSO ucode(1), btou(1), ppu(1)