[partial backport of gcc-4.9/trunk r198344 to fix a target-breaking
 typo in LRA <mikpe@it.uu.se>]

List-Archive: <http://gcc.gnu.org/ml/gcc/>
Date: Tue, 09 Jul 2013 22:51:16 +0100
From: David Given <dg at cowlark dot com>
Subject: HAVE_ATTR_enabled mishandling?

I think I have found a bug. This is in stock gcc 4.8.1...

My backend does not use the 'enabled' attribute; therefore the following
code in insn-attr.h kicks in:

  #ifndef HAVE_ATTR_enabled
  #define HAVE_ATTR_enabled 0
  #endif

Therefore the following code in gcc/lra-constraints.c is enabled:

  #ifdef HAVE_ATTR_enabled
      if (curr_id->alternative_enabled_p != NULL
	  && ! curr_id->alternative_enabled_p[nalt])
	continue;
  #endif

->alternative_enabled_p is bogus; therefore segfault.

Elsewhere I see structures of the form:

  #if HAVE_ATTR_enabled
  ...
  #endif

So I think that #ifdef above is a straight typo. Certainly, changing it
to a #if makes the crash go away...

List-Archive: <http://gcc.gnu.org/ml/gcc/>
Date: Fri, 12 Jul 2013 02:35:53 +0800
From: Chung-Ju Wu <jasonwucj at gmail dot com>
Subject: Re: HAVE_ATTR_enabled mishandling?

I faced exactly the same problem as yours.

When I was trying to enable LRA on my target, I got segfault as well
because I did not have 'enabled' attribute in my target.md file.

I was told it was due to my faulty md design.  The simplest workaround
is to define 'enabled' attribute so I took it.  But I suspected that
may be a latent issue.

It's so happy to see others have the same question and provide a solution.
Certainly, whether your solution is correct should be reviewed by LRA
maintainer, Vladmir Makarov, so I cc him in the list.

gcc/

2013-04-26  Vladimir Makarov  <vmakarov@redhat.com>

	* lra-constraints.c (process_alt_operands): Use #if
	HAVE_ATTR_enabled instead of #ifdef.

--- gcc-4.8.1/gcc/lra-constraints.c.~1~	2013-05-02 21:16:29.000000000 +0200
+++ gcc-4.8.1/gcc/lra-constraints.c	2013-07-13 09:38:03.060435343 +0200
@@ -1388,7 +1388,7 @@ process_alt_operands (int only_alternati
   for (nalt = 0; nalt < n_alternatives; nalt++)
     {
       /* Loop over operands for one constraint alternative.  */
-#ifdef HAVE_ATTR_enabled
+#if HAVE_ATTR_enabled
       if (curr_id->alternative_enabled_p != NULL
 	  && ! curr_id->alternative_enabled_p[nalt])
 	continue;