[PATCH] Add word-sized conversion functions to libgcc2

[Richard Sandiford]

DJ Delorie <dj@redhat.com> writes:
>>   - Make compiling libgcc2.c a no-op if LIBGCC2_UNITS_PER_WORD
>>     > MIN_UNITS_PER_WORD.
>
> This totally breaks m32c-elf, which has MIN_UNITS_PER_WORD == 2 and
> LIBGCC_UNITS_PER_WORD == 4.  The whole file goes away and nearly every
> program stops compiling.

I'm sorry.  (I seem to be saying that a lot recently.)

> m32c-elf is a 16 bit port with 64 bit "long long", which forces
> libgcc2's units per word to 4:
>
> # elif (MIN_UNITS_PER_WORD > 2 \
>         || (MIN_UNITS_PER_WORD > 1 && LONG_LONG_TYPE_SIZE > 32))
> #  define LIBGCC2_UNITS_PER_WORD 4

And that value fails the:

#if LIBGCC2_UNITS_PER_WORD <= MIN_UNITS_PER_WORD

guard.  Duh.  I'd forgotten that the default LIBGCC2_UNITS_PER_WORD
could be greater than MIN_UNITS_PER_WORD.

The default LIBGCC2_UNITS_PER_WORD settings are really calculating the
maximum "word" size that is safe to use, given that we also need a valid
"doubleword".  And to recap, the SIDITI stuff that I added could ask for
both a smaller word size (for SI and DI stuff on 64-bit targets) or a
larger word size (for TI stuff on 32-bit targets).  The latter should
result in an empty file.

So, the patch below separates the two concepts.  I've introduced
a LIBGCC2_MAX_UNITS_PER_WORD and then used that as the default
definition of LIBGCC2_UNITS_PER_WORD.  The guard now checks against
LIBGCC2_MAX_UNITS_PER_WORD rather than MIN_UNITS_PER_WORD.

I've tested that m32c-elf builds non-empty libgcc files with this patch.
(There was a later spill failure building newlib.)  I've also bootstrapped
& regression tested on x86_64-linux-gnu and tested on mips64-linux-gnu.
OK to isntall?

Richard


	* libgcc2.c (LIBGCC2_MAX_UNITS_PER_WORD): New macro.
	(LIBGCC2_UNITS_PER_WORD): Use LIBGCC2_MAX_UNITS_PER_WORD rather
	than MIN_UNITS_PER_WORD to set the default, and in the guard.

Index: gcc/libgcc2.c
===================================================================
*** gcc/libgcc2.c	(revision 114013)
--- gcc/libgcc2.c	(working copy)
*************** #define ATTRIBUTE_HIDDEN
*** 44,61 ****
  #define MIN_UNITS_PER_WORD UNITS_PER_WORD
  #endif
  
  #ifndef LIBGCC2_UNITS_PER_WORD
! # if MIN_UNITS_PER_WORD > 4
! #  define LIBGCC2_UNITS_PER_WORD 8
! # elif (MIN_UNITS_PER_WORD > 2 \
!         || (MIN_UNITS_PER_WORD > 1 && LONG_LONG_TYPE_SIZE > 32))
! #  define LIBGCC2_UNITS_PER_WORD 4
! # else
! #  define LIBGCC2_UNITS_PER_WORD MIN_UNITS_PER_WORD
! # endif
  #endif
  
! #if LIBGCC2_UNITS_PER_WORD <= MIN_UNITS_PER_WORD
  
  #include "libgcc2.h"
  
--- 44,66 ----
  #define MIN_UNITS_PER_WORD UNITS_PER_WORD
  #endif
  
+ /* Work out the largest "word" size that we can deal with on this target.  */
+ #if MIN_UNITS_PER_WORD > 4
+ # define LIBGCC2_MAX_UNITS_PER_WORD 8
+ #elif (MIN_UNITS_PER_WORD > 2 \
+        || (MIN_UNITS_PER_WORD > 1 && LONG_LONG_TYPE_SIZE > 32))
+ # define LIBGCC2_MAX_UNITS_PER_WORD 4
+ #else
+ # define LIBGCC2_MAX_UNITS_PER_WORD MIN_UNITS_PER_WORD
+ #endif
+ 
+ /* Work out what word size we are using for this compilation.
+    The value can be set on the command line.  */
  #ifndef LIBGCC2_UNITS_PER_WORD
! #define LIBGCC2_UNITS_PER_WORD LIBGCC2_MAX_UNITS_PER_WORD
  #endif
  
! #if LIBGCC2_UNITS_PER_WORD <= LIBGCC2_MAX_UNITS_PER_WORD
  
  #include "libgcc2.h"