Re: [patch] libffi, fix powerpc-unknown-freebsd

[Andreas Tobler <andreast-list at fgznet dot ch>]

David Edelsohn wrote:
> 	* src/powerpc/ffitarget.h (ffi_abi): Add FFI_LINUX and
> 	FFI_LINUX_SOFT_FLOAT to the POWERPC_FREEBSD enum.
> 	Adjust copyright notice.
> 	* src/powerpc/ffi.c (ffi_prep_cif_machdep): Fix bit position
> 	calculation for FFI_SYSV_TYPE_SMALL_STRUCT.
> 	(ffi_closure_helper_SYSV): Fix return type for
> 	FFI_SYSV_TYPE_SMALL_STRUCT.
> 	Adjust copyright notice.
>
> Okay.
>
> Please add more documentation for FFI_SYSV_TYPE_SMALL_STRUCT -- what
> it represents and that it uses two bits.

Sigh, I expected that... I should know you :)

Here another iteration.

Instead of playing with FFI_SYSV_TYPE_SMALL_STRUCT for bit shifts I 
introduced two new flags which tell us if we need r3 or r3 and r4 for 
structs passing.

The issue is this, I need to tell the ppc_closure.S exactly which type I 
expect when returning. And unfortunatley the implementation needs a 
distinction for every type and size. Type 1 to 15 are already used, so I 
can start with using type 16 and up.

If it is still not clear, let me know, I try to be more verbose then.

The attached patch was tested under fbsd-7.0 gcc-4.3 and trunk.
Currently a ppc-linux build is running for base config and also for 
soft-float.


2008-08-21  Andreas Tobler  <a.tobler@schweiz.org>

	* src/powerpc/ffitarget.h (ffi_abi): Add FFI_LINUX and
	FFI_LINUX_SOFT_FLOAT to the POWERPC_FREEBSD enum.
	Adjust copyright notice.
	* src/powerpc/ffi.c: Add two new flags to indicate if we have one
	register or two register to use for FFI_SYSV structs.
	(ffi_prep_cif_machdep): Pass the right register flag introduced above.
	(ffi_closure_helper_SYSV): Fix the return type for
	FFI_SYSV_TYPE_SMALL_STRUCT. Comment.
	Adjust copyright notice.

Index: src/powerpc/ffitarget.h
===================================================================
--- src/powerpc/ffitarget.h	(revision 139412)
+++ src/powerpc/ffitarget.h	(working copy)
@@ -1,6 +1,6 @@
 /* -----------------------------------------------------------------*-C-*-
    ffitarget.h - Copyright (c) 1996-2003  Red Hat, Inc.
-   Copyright (C) 2007 Free Software Foundation, Inc
+   Copyright (C) 2007, 2008 Free Software Foundation, Inc
    Target configuration macros for PowerPC.
 
    Permission is hereby granted, free of charge, to any person obtaining
@@ -77,6 +77,8 @@
   FFI_SYSV,
   FFI_GCC_SYSV,
   FFI_LINUX64,
+  FFI_LINUX,
+  FFI_LINUX_SOFT_FLOAT,
   FFI_DEFAULT_ABI = FFI_SYSV,
 #endif
 
Index: src/powerpc/ffi.c
===================================================================
--- src/powerpc/ffi.c	(revision 139412)
+++ src/powerpc/ffi.c	(working copy)
@@ -1,6 +1,6 @@
 /* -----------------------------------------------------------------------
    ffi.c - Copyright (c) 1998 Geoffrey Keating
-   Copyright (C) 2007 Free Software Foundation, Inc
+   Copyright (C) 2007, 2008 Free Software Foundation, Inc
 
    PowerPC Foreign Function Interface
 
@@ -43,6 +43,10 @@
 
   FLAG_RETURNS_128BITS  = 1 << (31-27), /* cr6  */
 
+  FLAG_SYSV_SMST_R4     = 1 << (31-16), /* cr4, use r4 for FFI_SYSV 8 byte
+					   structs.  */
+  FLAG_SYSV_SMST_R3     = 1 << (31-15), /* cr3, use r3 for FFI_SYSV 4 byte
+					   structs.  */
   FLAG_ARG_NEEDS_COPY   = 1 << (31- 7),
   FLAG_FP_ARGUMENTS     = 1 << (31- 6), /* cr1.eq; specified by ABI */
   FLAG_4_GPR_ARGUMENTS  = 1 << (31- 5),
@@ -679,14 +683,14 @@
 		 The same applies for the structs returned in r3/r4.  */
 	      if (size <= 4)
 		{
-		  flags |= 1 << (31 - FFI_SYSV_TYPE_SMALL_STRUCT - 1);
+		  flags |= FLAG_SYSV_SMST_R3;
 		  flags |= 8 * (4 - size) << 4;
 		  break;
 		}
 	      /* These structs are returned in r3 and r4. See above.   */
 	      if  (size <= 8)
 		{
-		  flags |= 1 << (31 - FFI_SYSV_TYPE_SMALL_STRUCT - 2);
+		  flags |= FLAG_SYSV_SMST_R4;
 		  flags |= 8 * (8 - size) << 4;
 		  break;
 		}
@@ -1248,10 +1252,15 @@
 
   /* Tell ffi_closure_SYSV how to perform return type promotions.
      Because the FFI_SYSV ABI returns the structures <= 8 bytes in r3/r4
-     we have to tell ffi_closure_SYSV how to treat them.  */
+     we have to tell ffi_closure_SYSV how to treat them. We combine the base
+     type FFI_SYSV_TYPE_SMALL_STRUCT - 1  with the size of the struct.
+     So a one byte struct gets the return type 16. Return type 1 to 15 are
+     already used and we never have a struct with size zero. That is the reason
+     for the subtraction of 1. See the comment in ffitarget.h about ordering.
+  */
   if (cif->abi == FFI_SYSV && cif->rtype->type == FFI_TYPE_STRUCT
       && size <= 8)
-    return FFI_SYSV_TYPE_SMALL_STRUCT + size;
+    return (FFI_SYSV_TYPE_SMALL_STRUCT - 1) + size;
 #if FFI_TYPE_LONGDOUBLE != FFI_TYPE_DOUBLE
   else if (cif->rtype->type == FFI_TYPE_LONGDOUBLE
 	   && cif->abi != FFI_LINUX && cif->abi != FFI_LINUX_SOFT_FLOAT)