[amdgcn] Add support for sub-word sync_compare_and_swap operations

2020-01-09  Kwok Cheung Yeung  <kcy@codesourcery.com>

	libgcc/
	* config/gcn/atomic.c: New.
	* config/gcn/t-amdgcn (LIB2ADD): Add atomic.c.

From-SVN: r280055

libgcc/ChangeLog

+2020-01-09  Kwok Cheung Yeung  <kcy@codesourcery.com>
+
+	* config/gcn/atomic.c: New.
+	* config/gcn/t-amdgcn (LIB2ADD): Add atomic.c.
+
 2020-01-08  Georg-Johann Lay  <avr@gjlay.de>
 
 	Implement 64-bit double functions.

libgcc/config/gcn/atomic.c

+/* AMD GCN atomic operations
+   Copyright (C) 2020 Free Software Foundation, Inc.
+   Contributed by Mentor Graphics.
+
+   This file is free software; you can redistribute it and/or modify it
+   under the terms of the GNU General Public License as published by the
+   Free Software Foundation; either version 3, or (at your option) any
+   later version.
+
+   This file is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   Under Section 7 of GPL version 3, you are granted additional
+   permissions described in the GCC Runtime Library Exception, version
+   3.1, as published by the Free Software Foundation.
+
+   You should have received a copy of the GNU General Public License and
+   a copy of the GCC Runtime Library Exception along with this program;
+   see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#define __SYNC_SUBWORD_COMPARE_AND_SWAP(TYPE, SIZE)			     \
+									     \
+TYPE									     \
+__sync_val_compare_and_swap_##SIZE (TYPE *ptr, TYPE oldval, TYPE newval)     \
+{									     \
+  unsigned int *wordptr = (unsigned int *)((uintptr_t) ptr & ~3UL);	     \
+  int shift = ((uintptr_t) ptr & 3UL) * 8;				     \
+  unsigned int valmask = (1 << (SIZE * 8)) - 1;				     \
+  unsigned int wordmask = ~(valmask << shift);				     \
+  unsigned int oldword = *wordptr;					     \
+  for (;;)								     \
+    {									     \
+      TYPE prevval = (oldword >> shift) & valmask;			     \
+      if (__builtin_expect (prevval != oldval, 0))			     \
+	return prevval;							     \
+      unsigned int newword = oldword & wordmask;			     \
+      newword |= ((unsigned int) newval) << shift;			     \
+      unsigned int prevword						     \
+	  = __sync_val_compare_and_swap_4 (wordptr, oldword, newword);	     \
+      if (__builtin_expect (prevword == oldword, 1))			     \
+	return oldval;							     \
+      oldword = prevword;						     \
+    }									     \
+}									     \
+									     \
+bool									     \
+__sync_bool_compare_and_swap_##SIZE (TYPE *ptr, TYPE oldval, TYPE newval)    \
+{									     \
+  return __sync_val_compare_and_swap_##SIZE (ptr, oldval, newval) == oldval; \
+}
+
+__SYNC_SUBWORD_COMPARE_AND_SWAP (unsigned char, 1)
+__SYNC_SUBWORD_COMPARE_AND_SWAP (unsigned short, 2)
+

libgcc/config/gcn/t-amdgcn

-LIB2ADD += $(srcdir)/config/gcn/lib2-divmod.c \
+LIB2ADD += $(srcdir)/config/gcn/atomic.c \
+	   $(srcdir)/config/gcn/lib2-divmod.c \
 	   $(srcdir)/config/gcn/lib2-divmod-hi.c \
 	   $(srcdir)/config/gcn/unwind-gcn.c