Re: Fix gcc bootstrap problem

[Andrew Pinski]

On 8/20/07, Nick Clifton <[EMAIL PROTECTED]> wrote:
> bfd/ChangeLog
> 2007-08-20  Nick Clifton  <[EMAIL PROTECTED]>
>
> * elflink.c (elf_fixup_link_order): Rewrite conversion of
> s->alignment_power into an offset mask in order to avoid a gcc
> error message.

This is wrong, this error message is really an internal error (witness
the ICE after the error).  We really should be using inform (or a
different from error) for these internal error message.

Can you provide me (or file a bug) with the preprocessed source for
this ICE?  The "i386-dis.c" ICE is most likely PR 22371.

Thanks,
Andrew Pinski

Fix gcc bootstrap problem

[Nick Clifton]

Hi Guys,

  I ran a x86 hosted bootstrap of the mainline gcc and binutils
  sources over the weekend and it failed with this error report:

bfd/elflink.c: In function 'elf_fixup_link_order':
bfd/elflink.c:9893: error: type mismatch in unary expression
long unsigned int
int
D.16764 = -D.16763

  Not exactly the most helpful error report in the world, but with a
  set of tree dumps and a bit of guesswork I tracked the problem down
  to this line:

offset &= ~(bfd_vma)((1 << s->alignment_power) - 1);

  Gcc has worked out that "~ foo - 1" is the same as "- foo" but it
  has failed to appreciate that the (bfd_vma) cast should apply to the
  constant 1 as well as the expression (1 << s->alignment_power).  So
  it thinks that the expression above is equivalent to (paraphrasing
  slightly): 

unsigned long int D.16764;
signed int D.16763;

D.16763 = 1 << s->alignment_power;
D.16764 = - D.16763;

offset = offset & D.16764;

  Hence it is complaining about the unary conversion of D.16763 into
  D.16764.  I think that this is probably a gimplification bug but
  that is beyond me, so I have Cc'ed this email to the gcc bugs list.
  In the meantime however I have hit on a simple workaround:
  
offset &= (bfd_vma)~((1 << s->alignment_power) - 1);

  (ie moving the cast to a (bfd_vma) to before the inversion
  operator).  This works in the bootstrap although it would fail if
  the alignment power is sufficiently large to cause the left shift to
  overflow an integer.  So I am going to check in a variant of this
  change:

offset &= (bfd_vma)~((1L << s->alignment_power) - 1L);

  which I think should satisfy everyone.  I will also check the patch
  into the 2.18 branch.

Cheers
  Nick

PS.  The bootstrap still does not succeed with this patch
  installed.  It fails later on with this error report:

  i386-dis.c:4213: error: type mismatch in pointer plus expression
struct dis386 *
struct dis386[8] *
unsigned int 
dp = &float_reg + D.7721

  I am looking into this now.
  
bfd/ChangeLog
2007-08-20  Nick Clifton  <[EMAIL PROTECTED]>

* elflink.c (elf_fixup_link_order): Rewrite conversion of
s->alignment_power into an offset mask in order to avoid a gcc
error message.

Index: bfd/elflink.c
===
RCS file: /cvs/cvsfiles/devo/bfd/elflink.c,v
retrieving revision 1.95
diff -c -3 -p -r1.95 elflink.c
*** bfd/elflink.c   19 Aug 2007 17:49:44 -  1.95
--- bfd/elflink.c   20 Aug 2007 07:39:30 -
*** elf_fixup_link_order (bfd *abfd, asectio
*** 9965,9971 
for (n = 0; n < seen_linkorder; n++)
  {
s = sections[n]->u.indirect.section;
!   offset &= ~(bfd_vma)((1 << s->alignment_power) - 1);
s->output_offset = offset;
sections[n]->offset = offset;
offset += sections[n]->size;
--- 9965,9971 
for (n = 0; n < seen_linkorder; n++)
  {
s = sections[n]->u.indirect.section;
!   offset &= (bfd_vma)~((1L << s->alignment_power) - 1L);
s->output_offset = offset;
sections[n]->offset = offset;
offset += sections[n]->size;