Add support for the Win32 hook prologue (try 8)

[Stefan Dösinger <stefan at codeweavers dot com>]

Here's another version of the ms_hook_prologue patch.

I noticed that the function context isn't set, and the  
current_function_decl isn't updated by the time the attribute  
callbacks execute. Thus I use current_function_decl, not  
decl_function_context(node) to find out if the function is nested or  
not. If this is not correct(I only checked the C frontend so far),  
please suggest a better solution. The only other way I found was to  
check the nestedness during code generation, which doesn't seem right  
to me(and puts the error at the end of the function, not its  
declaration).

The development / test platform for this patch is x86_64-apple- 
darwin10.0.0 on OSX 10.6.1. I have tested older versions of this on  
x86_64-pc-linux-gnu as well, but didn't run the testsuite for this  
patch on Linux yet.

Changes from try 7:
Disallowed ms_hook_prologue on nested functions
Attached the correct patch this time

Changes from try 6:
the ms_hook_prologue attribute applies to the function, rather than  
its type. Changed the attribute lookup accordingly. However, I still  
allow the attribute for nested functions, there's no reason why this  
wouldn't work. (The case of static_chain and ms_hook_prologue can  
potentially be optimized)

Changes from try 5:
Fixed conflicts with static_chain patches, simple handling for
static_chain+ms_hook_prologue cases.
Improved changelog(hopefully correctly)

Changes from try 4:
Use SIMode instead of Pmode for the registers.

Changes from try 3:
Renamed the attribute name to ms_hook_prologue, since its not always  
generated
by msvc

Changes from try 2:
* Use dg-require-effective-target ilp32 instead of dg-options -m32 in  
the test
* More code layout fixes

Changes from the first try:
* Moved testcase to gcc.target/i386
* restructured ix86_handle_abi_attribute
* Changed HAVE_AS_IX86_SWAP handling as suggested by rth
* ix86_function_msvc_prologue returns a bool, removed fntype != NULL  
check
* fixed indentation in ix86_expand_prologue(hopefully correct now)

2009-09-23: Stefan Dösinger <stefan@codeweavers.com
      * config/i386/i386.md: Added vswapmov, a volative DIMode
         register->register mov with the swap suffix set

      * config/i386/i386.c (ix86_expand_prologue): Add a new function
      attribute ms_hook_prologue that starts functions with the same  
opcode
      sequence used in most Win32 API functions

      * config/i386/i386.c (ix86_function_ms_hook_prologue): New
      * config/i386/i386.c (ix86_handle_fndecl_attribute): New

      * gcc.target/i386/ms_hook_prologue.c: New testcase

      * configure.ac: Test for swap suffix support in as

Attachment: ms_hook_prologue.diff
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