spike(1)						      General Commands Manual							  spike(1)

NAME

       spike - Performs code optimization after linking a program

SYNOPSIS

       spike binary_file [options...]

OPTIONS

       Names  the  optimized  binary output file. The default file name is a.out.  Causes spike to use the feedback database stored in file, where
       file is the name of the input executable. This database is created by first compiling the program with the -feedback option  (for  example,
       cc  -feedback  prog)  and  then	instrumenting  and  running  the program with the pixie -update or prof -pixie -update command (see cc(1),
       pixie(1), and prof(1)).	Causes spike to use file.Addrs (basic block addresses file) and file.Counts (basic block counts file) for profile-
       based  optimization.   These  files  are produced by the pixie tool (see pixie(1) and prof(1)).	spike can be applied only to V5.1 or later
       kernels.  Use this option when applying spike to the UNIX kernel (vmunix).  Disables code layout optimization that splits  procedures  into
       multiple  parts.   Disables  basic  block chaining, which arranges code so that the fall through path is the commonly taken path.  Disables
       procedure ordering.  Reduces the number of padding nops inserted into the code to align instructions. The alignment usually makes the  code
       run faster, but makes the code larger, which can cause more instruction cache misses.  Adjusts the threshold used by procedure splitting in
       code layout to decide which code is frequently and infrequently executed. The default is that make up at least 99 percent of the  estimated
       execution  time are considered frequently executed and the rest are marked as infrequently executed. Increasing the threshold can help when
       the profile is not representative. For example, try a value of Displays the version number of spike.

OPERANDS

       Name of the binary file to which spike is to be applied.

DESCRIPTION

       spike is a tool for performing code optimization after linking. It is a replacement for om and does similar optimizations. Because  it  can
       operate on an entire program, spike is able to do optimizations that cannot be done by the compiler.

       Some  of the optimizations that spike performs are code layout, deleting unreachable code, and optimization of address computations.  spike
       is most effective when it uses profile information to guide optimization.

       spike can process binaries linked on Tru64 UNIX (formerly Digital UNIX) Version 4.0 or later systems. Binaries that are linked  on  Version
       5.1 or later systems contain information that allows spike to do additional optimization.

       You  can  use  spike in two ways: By applying the spike command to a binary file after compilation.  As part of the compilation process, by
       specifying the -spike option with the cc command (or the cxx, f77, or f90 command, if the associated compiler is installed).

       The -spike option is more convenient when you are not using profile information (Example 2), or you are using profile  information  in  the
       compiler,  too  (Example  3). The spike command is more convenient if you do not want to relink the executable (Example 1) or you are using
       profile information after compilation (Examples 4 and 5).

       All spike command options can be passed directly to the cc command's -spike option by using the (cc) -WS option. Example 6 shows  the  syn-
       tax.

RESTRICTIONS

       spike  cannot  process  images that have been stripped.	contain RPDR tables (see Section 2.3.7, Special Symbols, of the Object File/Symbol
       Table Format Specification) compute an offset from a code address.  modify the text section at runtime.

       Using cord, atom, pixie, hiprof, or third on an image that has been processed with spike is unsupported.

NOTES

       spike tries to update the symbol table in the binary so that the optimized binary can be debugged. As with  other  compiler  optimizations,
       there  may be some situations where the debugger may not be able to properly report the current location in the program or display the val-
       ues of variables.  If spike divides a procedure into multiple disjoint parts, the main body will keep the original procedure name, but  the
       other parts will have names that are the original name with _cold_n (where n is a number) appended to the end.

EXAMPLES

       In  the	following  example,  spike  is	applied  to the binary my_prog, producing the optimized output file prog1.opt.	% spike my_prog -o
       prog1.opt In the following example, spike is applied during compilation with the cc command's -spike option: % cc -c file1.c % cc -o  prog3
       file1.o -spike

	      The  first command line creates the object file file1.o.	The second command line links file1.o into an executable and uses spike to
	      optimize the executable.	The following example shows how to optimize a program, prog, by first  compiling  it  with  the  -feedback
	      option, then merging profiling statistics from two instrumented runs of the program, then compiling it with the -spike and -feedback
	      options so the feedback information stored in the executable is used by the compiler and spike: % cc -feedback prog -o  prog  *.c  %
	      pixie  -pids prog % prog.pixie (input set 1) % prog.pixie (input set 2) % prof -pixie -update prog prog.Counts.*	% cc -spike -feed-
	      back prog -o prog *.c

	      The first compilation produces an augmented executable that will later accept feedback information.

	      The pixie command creates an instrumented program (prog.pixie), which is then run twice. The -pids option adds  the  process  ID	of
	      each test run to the name of the profiling data file produced -- for example prog.Counts.371 and prog.Counts.422.

	      The prof -pixie command merges the two data files.  The -update option updates the executable, prog, with the combined information.

	      The  program  is	compiled with the -spike and -feedback options so the feedback information stored in the executable is used by the
	      compiler and spike.  The following example shows how to optimize a program, prog, by first compiling it with the	-feedback  option,
	      then  merging  profiling	statistics from two instrumented runs of the program, then applying the spike -feedback command to use the
	      feedback information stored in the executable: % cc -feedback prog -o prog *.c % pixie -pids prog  %  prog.pixie	(input	set  1)  %
	      prog.pixie (input set 2) % prof -pixie -update prog prog.Counts.*  % spike prog -feedback prog -o prog.opt

	      As in the previous example, the first compilation produces an augmented executable. The instrumented program is run twice, producing
	      a uniquely named data file each time. The prof -pixie -update command merges the two data files and updates the executable with  the
	      combined information.

	      The  spike  -feedback  command uses the combined profiling information to produce the optimized output file prog.opt.  The following
	      example shows how to optimize a program, prog, by merging profiling statistics from two  instrumented  runs  of  the  program,  then
	      applying	the  spike  -fb  command  to  use  the	feedback  information in the and files: % cc prog -o prog *.c % pixie -pids prog %
	      prog.pixie (input set 1) % prog.pixie (input set 2) % prof -pixie -merge prog.Counts prog prog.Addrs prog.Counts.*  % spike prog -fb
	      prog -o prog.opt

	      The  first  compilation produces a normal executable. As in the previous example, the instrumented program is run twice, producing a
	      uniquely named data file each time.

	      The prof -pixie -merge command merges the two data files into one combined prog.Counts file.

	      The spike -fb command uses the information in prog.Addrs and prog.Counts to produce the optimized output file prog.opt.

	      The method in Example 4 is preferred. You should use the method in Example 5 only if you cannot compile with  the  -feedback  option
	      that  uses  feedback information stored in the executable.  The following example shows the syntax for passing spike command options
	      to the (cc) -spike option by using the (cc) -WS option: % cc -spike -feedback prog -o prog *.c 
		   -WS,-splitThresh,.999,-noaggressiveAlign

RETURN STATUS

       spike returns the following status values:

       0:	  Success
       Nonzero:   Error

SEE ALSO

       cc(1), pixie(1), prof(1)

       Programmer's Guide

																	  spike(1)