[PATCH, committed] Fix up documentation about tm_p.h

[Michael Meissner]

I checked in the following patch to update the documentation for tm_p.h.  I
noticed the FIXME comment in the texi source when I was working on my previous
patch for combining the standard and machine dependent builtin indexes.  While
that patch did not go in, I figured I could improve the documentation for
tm_p.h.

2011-09-06  Michael Meissner  <meissner@linux.vnet.ibm.com>

	* doc/configfiles.texi (Configuration Files): Update documentation
	about tm_p.h and remove FIXME comment.

Index: gcc/doc/configfiles.texi
===================================================================
--- gcc/doc/configfiles.texi	(revision 178609)
+++ gcc/doc/configfiles.texi	(working copy)
@@ -59,6 +59,14 @@ these include the autoconfigured headers
 machine.
 @item
 @file{tm_p.h}, which includes the header @file{@var{machine}-protos.h}
-that contains prototypes for functions in the target @file{.c} file.
-FIXME: why is such a separate header necessary?
+that contains prototypes for functions in the target
+@file{@var{machine}.c} file.  The header @file{@var{machine}-protos.h}
+can include prototypes of functions that use rtl and tree data
+structures inside appropriate @code{#ifdef RTX_CODE} and @code{#ifdef
+TREE_CODE} conditional code segements.  The
+@file{@var{machine}-protos.h} is included after the @file{rtl.h}
+and/or @file{tree.h} would have been included.  The @file{tm_p.h} also
+includes the header @file{tm-preds.h} which is generated by
+@file{genpreds} program during the build to define the declarations
+and inline functions for the predicate functions.
 @end itemize

-- 
Michael Meissner, IBM
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