From 24a40b356f07a2a4d50d4c36e5bbb86ef06d3925 Mon Sep 17 00:00:00 2001
From: Nathan Sidwell <nathan@codesourcery.com>
Date: Wed, 22 Apr 2009 10:53:53 +0000
Subject: [PATCH] gthr-vxworks.h (struct __gthread_once_t): Add alignment and
 padding for PPC.

	* gthr-vxworks.h (struct __gthread_once_t): Add alignment and
	padding for PPC.
	(__GTHREAD_ONCE_INIT): Adjust ppc initializer.
	* config/vxlib.c (__gthread_once): Add race guard for PPC.

From-SVN: r146566
---
 gcc/ChangeLog      |  7 +++++++
 gcc/config/vxlib.c | 10 +++++++++-
 gcc/gthr-vxworks.h | 23 +++++++++++++++++++----
 3 files changed, 35 insertions(+), 5 deletions(-)

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index d7270194d26b..056f732dd586 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2009-04-22  Nathan Sidwell  <nathan@codesourcery.com>
+
+	* gthr-vxworks.h (struct __gthread_once_t): Add alignment and
+	padding for PPC.
+	(__GTHREAD_ONCE_INIT): Adjust ppc initializer.
+	* config/vxlib.c (__gthread_once): Add race guard for PPC.
+
 2009-04-22  Paolo Bonzini  <bonzini@gnu.org>
 
 	* config/sh/sh.c (shift_insns_rtx, shiftcosts, gen_shifty_op,
diff --git a/gcc/config/vxlib.c b/gcc/config/vxlib.c
index 686d66de01f9..0ff996cfced8 100644
--- a/gcc/config/vxlib.c
+++ b/gcc/config/vxlib.c
@@ -65,7 +65,15 @@ __gthread_once (__gthread_once_t *guard, void (*func)(void))
   __gthread_lock_library ();
 #else
   while (!vxTas ((void *)&guard->busy))
-    taskDelay (1);
+    {
+#ifdef __PPC__
+      /* This can happen on powerpc, which is using all 32 bits
+	 of the gthread_once_t structure.  */
+      if (guard->done)
+	return;
+#endif
+      taskDelay (1);
+    }
 #endif
 
   /* Only one thread at a time gets here.  Check ->done again, then
diff --git a/gcc/gthr-vxworks.h b/gcc/gthr-vxworks.h
index c2fb8e6729f0..dee15731f0ac 100644
--- a/gcc/gthr-vxworks.h
+++ b/gcc/gthr-vxworks.h
@@ -115,17 +115,32 @@ __gthread_recursive_mutex_unlock (__gthread_recursive_mutex_t *mutex)
 
 typedef struct
 {
-#ifndef __RTP__
+#if !defined(__RTP__)
+#if defined(__PPC__)
+  __attribute ((aligned (__alignof (unsigned))))
+#endif
   volatile unsigned char busy;
 #endif
   volatile unsigned char done;
+#if !defined(__RTP__) && defined(__PPC__)
+  /* PPC's test-and-set implementation requires a 4 byte aligned
+     object, of which it only sets the first byte.  We use padding
+     here, in order to maintain some amount of backwards
+     compatibility.  Without this padding, gthread_once objects worked
+     by accident because they happen to be static objects and the ppc
+     port automatically increased their alignment to 4 bytes.  */
+  unsigned char pad1;
+  unsigned char pad2;
+#endif
 }
 __gthread_once_t;
 
-#ifndef __RTP__
-# define __GTHREAD_ONCE_INIT { 0, 0 }
-#else
+#if defined (__RTP__)
 # define __GTHREAD_ONCE_INIT { 0 }
+#elif defined (__PPC__) 
+# define __GTHREAD_ONCE_INIT { 0, 0, 0, 0 }
+#else
+# define __GTHREAD_ONCE_INIT { 0, 0 }
 #endif
 
 extern int __gthread_once (__gthread_once_t *__once, void (*__func)(void));