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* gprof.texi: Refer readers to the gcov tool if they want line-by-line profiling.

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Nick Clifton 2007-06-20 09:03:52 +00:00
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@ -1,3 +1,8 @@
2007-06-20 Nick Clifton <nickc@redhat.com>
* gprof.texi: Refer readers to the gcov tool if they want
line-by-line profiling.
2007-06-14 H.J. Lu <hongjiu.lu@intel.com> 2007-06-14 H.J. Lu <hongjiu.lu@intel.com>
* Makefile.am (ACLOCAL_AMFLAGS): Add -I ../config -I ../bfd. * Makefile.am (ACLOCAL_AMFLAGS): Add -I ../config -I ../bfd.

68
gprof/gprof.texi
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@ -334,30 +334,17 @@ will not affect the flat profile (except that the @code{calls} field for
the functions will be blank), but will greatly reduce the usefulness of the the functions will be blank), but will greatly reduce the usefulness of the
call graph. call graph.
If you wish to perform line-by-line profiling, If you wish to perform line-by-line profiling you should use the
you will also need to specify the @samp{-g} option, @code{gcov} tool instead of @code{gprof}. See that tool's manual or
instructing the compiler to insert debugging symbols into the program info pages for more details of how to do this.
that match program addresses to source code lines.
@xref{Line-by-line, ,Line-by-line Profiling}.
In addition to the @samp{-pg} and @samp{-g} options, older versions of Note, older versions of @code{gcc} produce line-by-line profiling
GCC required you to specify the @samp{-a} option when compiling in information that works with @code{gprof} rather than @code{gcov} so
order to instrument it to perform basic-block counting. Newer there is still support for displaying this kind of information in
versions do not require this option and will not accept it; @code{gprof}. @xref{Line-by-line, ,Line-by-line Profiling}.
basic-block counting is always enabled when @samp{-pg} is on.
When basic-block counting is enabled, as the program runs It also worth noting that @code{gcc} implements a
it will count how many times it executed each branch of each @samp{if} @samp{-finstrument-functions} command line option which will insert
statement, each iteration of each @samp{do} loop, etc. This will
enable @code{gprof} to construct an annotated source code
listing showing how many times each line of code was executed.
It also worth noting that GCC supports a different profiling method
which is enabled by the @samp{-fprofile-arcs}, @samp{-ftest-coverage}
and @samp{-fprofile-values} switches. These switches do not produce
data which is useful to @code{gprof} however, so they are not
discussed further here. There is also the
@samp{-finstrument-functions} switch which will cause GCC to insert
calls to special user supplied instrumentation routines at the entry calls to special user supplied instrumentation routines at the entry
and exit of every function in their program. This can be used to and exit of every function in their program. This can be used to
implement an alternative profiling scheme. implement an alternative profiling scheme.
@ -696,7 +683,10 @@ symbols matching symspec @var{from} to those matching symspec @var{to}.
@itemx --line @itemx --line
The @samp{-l} option enables line-by-line profiling, which causes The @samp{-l} option enables line-by-line profiling, which causes
histogram hits to be charged to individual source code lines, histogram hits to be charged to individual source code lines,
instead of functions. instead of functions. This feature only works with programs compiled
by older versions of the @code{gcc} compiler. Newer versions of
@code{gcc} are designed to work with the @code{gcov} tool instead.
If the program was compiled with basic-block counting enabled, If the program was compiled with basic-block counting enabled,
this option will also identify how many times each line of this option will also identify how many times each line of
code was executed. code was executed.
@ -1407,9 +1397,16 @@ when recursion is going on.
@code{gprof}'s @samp{-l} option causes the program to perform @code{gprof}'s @samp{-l} option causes the program to perform
@dfn{line-by-line} profiling. In this mode, histogram @dfn{line-by-line} profiling. In this mode, histogram
samples are assigned not to functions, but to individual samples are assigned not to functions, but to individual
lines of source code. The program usually must be compiled lines of source code. This only works with programs compiled with
with a @samp{-g} option, in addition to @samp{-pg}, in order older versions of the @code{gcc} compiler. Newer versions of @code{gcc}
use a different program - @code{gcov} - to display line-by-line
profiling information.
With the older versions of @code{gcc} the program usually has to be
compiled with a @samp{-g} option, in addition to @samp{-pg}, in order
to generate debugging symbols for tracking source code lines. to generate debugging symbols for tracking source code lines.
Note, in much older versions of @code{gcc} the program had to be
compiled with the @samp{-a} command line option as well.
The flat profile is the most useful output table The flat profile is the most useful output table
in line-by-line mode. in line-by-line mode.
@ -1500,10 +1497,13 @@ which lists the program's source code, each function labeled with the
number of times it was called. You may also need to specify the number of times it was called. You may also need to specify the
@samp{-I} option, if @code{gprof} can't find the source code files. @samp{-I} option, if @code{gprof} can't find the source code files.
Compiling with @samp{gcc @dots{} -g -pg -a} augments your program With older versions of @code{gcc} compiling with @samp{gcc @dots{} -g
with basic-block counting code, in addition to function counting code. -pg -a} augments your program with basic-block counting code, in
This enables @code{gprof} to determine how many times each line addition to function counting code. This enables @code{gprof} to
of code was executed. determine how many times each line of code was executed. With newer
versions of @code{gcc} support for displaying basic-block counts is
provided by the @code{gcov} program.
For example, consider the following function, taken from gzip, For example, consider the following function, taken from gzip,
with line numbers added: with line numbers added:
@ -1701,15 +1701,7 @@ non-intrusive profiler, e.g.@: oprofile.
@item How do I find which lines in my program were executed the most times? @item How do I find which lines in my program were executed the most times?
Compile your program with basic-block counting enabled, run it, then Use the @code{gcov} program.
use the following pipeline:
@example
gprof -l -C @var{objfile} | sort -k 3 -n -r
@end example
This listing will show you the lines in your code executed most often,
but not necessarily those that consumed the most time.
@item How do I find which lines in my program called a particular function? @item How do I find which lines in my program called a particular function?