On Sun, Jun 04, 2017 at 08:12:49PM -0600, Sandra Loosemore wrote:
> On 05/29/2017 04:29 AM, Maxim Kuvyrkov wrote:
>
> >>diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> >>index 65308c9d933..6cbb77a8dc4 100644
> >>--- a/gcc/doc/invoke.texi
> >>+++ b/gcc/doc/invoke.texi
> >>@@ -11382,6 +11382,32 @@ of the function name, it is considered to be a
> >>match. For C99 and C++
> >> extended identifiers, the function name must be given in UTF-8, not
> >> using universal character names.
> >>
> >>+@item -fpatchable-function-entry=@var{N}[,@var{M}]
> >>+@opindex fpatchable-function-entry
> >>+Generate @var{N} NOPs right at the beginning
> >>+of each function, with the function entry point before the @var{M}th NOP.
> >>+If @var{M} is omitted, it defaults to @code{0} so the
> >>+function entry points to the address just at the first NOP.
> >>+The NOP instructions reserve extra space which can be used to patch in
> >>+any desired instrumentation at run time, provided that the code segment
> >>+is writable. The amount of space is controllable indirectly via
> >>+the number of NOPs; the NOP instruction is by default the one created
> >>+by @code{gen_nop ()}.
>
> This is too implementor-speaky. We shouldn't expect GCC users to read the
> source code to figure out what gen_nop is, or what it might do on any
> particular target.
In previous versions of the patch, some people had complained it was unclear
which NOP instruction would be used. Please make up your mind and suggest
a phrase, I'm open for suggestion, as you may already have noticed.
"by default, the default nop is used" sounds bad, IMHO.
Sandra, gen_nop picks the pattern the machine description provides for the
named instruction "nop". Richard wrote that every target is required to have
one.
> >>+The NOP instructions are inserted at -- and maybe before, depending on
> >>+@var{M} -- the function entry address, even before the prologue.
>
> Texinfo nit: s / -- /---/g
Ok, trivial.
> >>diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
> >>index c4f2c893c8e..4a5317d73bb 100644
> >>--- a/gcc/doc/tm.texi
> >>+++ b/gcc/doc/tm.texi
> >>@@ -4566,6 +4566,10 @@ will select the smallest suitable mode.
> >> This section describes the macros that output function entry
> >> (@dfn{prologue}) and exit (@dfn{epilogue}) code.
> >>
> >>+@deftypefn {Target Hook} void TARGET_ASM_PRINT_PATCHABLE_FUNCTION_ENTRY
> >>(FILE *@var{file}, unsigned HOST_WIDE_INT @var{patch_area_size}, bool
> >>@var{record_p})
> >>+Generate a patchable area at the function start
> >>+@end deftypefn
>
> This surely needs explanation of the parameters, and some punctuation.
Like
Generate a patchable area at a function start, consisting of
@var{patch_area_size} NOP instructions. Note the current location in
a dedicated segment if @var{record_p} is true.
?
Richard E.: we haven't heard a word from you yet about the actual code.
Torsten
