UOPT(1)UOPT(1)NAMEuopt - MIPS Ucode Global Optimizer
SYNOPSISuopt 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 printed. 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 same the 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
given 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 interpreted by uopt.
-v Turns on verbose mode. In this mode, uopt will print the name of
the procedure it's 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 Write 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.
Page 1
UOPT(1)UOPT(1)-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's 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, only at a reduced performance
level.
-pic2 Tells uopt that the program is being compiled for execution with
dynamic shared objects.
-nokpicopt
Asks uopt not to 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 given. 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
Page 2
UOPT(1)UOPT(1)
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 the given file to print diagnostic information during
optimization.
-Olimit count
Set this parameter to the given value. uopt will not optimize a
procedure whose size in terms of number of basic blocks exceeds
this value.
-loopunroll count
Set 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.
SEE ALSOucode(1), btou(1), ppu(1),
DIAGNOSTICSuopt assumes the input ucode file is error-free. However, it does output
warning messages when it runs into special situations during
optimization.
Page 3
