diff mbox

[cxx-mem-model,3/3] Fix mem_signal_fence and its fallbacks.

Message ID 1320295959-25005-3-git-send-email-rth@redhat.com
State New
Headers show

Commit Message

Richard Henderson Nov. 3, 2011, 4:52 a.m. UTC 
* builtins.c (HAVE_mem_thread_fence, gen_mem_thread_fence,
	HAVE_mem_signal_fence, gen_mem_signal_fence): Default.
	(expand_builtin_mem_thread_fence): Tidy.
	(expand_builtin_mem_signal_fence): Fallback to asm memory barrier.
---
 gcc/ChangeLog.mm |    7 +++++++
 gcc/builtins.c   |   50 +++++++++++++++++++++++++++++++++++++-------------
 2 files changed, 44 insertions(+), 13 deletions(-)
diff mbox

Patch

diff --git a/gcc/ChangeLog.mm b/gcc/ChangeLog.mm
index 24137ab..351b91f 100644
--- a/gcc/ChangeLog.mm
+++ b/gcc/ChangeLog.mm
@@ -1,5 +1,12 @@ 
 2011-11-02  Richard Henderson  <rth@redhat.com>
 
+	* builtins.c (HAVE_mem_thread_fence, gen_mem_thread_fence,
+	HAVE_mem_signal_fence, gen_mem_signal_fence): Default.
+	(expand_builtin_mem_thread_fence): Tidy.
+	(expand_builtin_mem_signal_fence): Fallback to asm memory barrier.
+
+2011-11-02  Richard Henderson  <rth@redhat.com>
+
 	* config/i386/i386.md (UNSPEC_MOVA): New.
 	* config/i386/sync.md (ATOMIC): New mode iterator.
 	(atomic_load<ATOMIC>, atomic_store<ATOMIC>): New.
diff --git a/gcc/builtins.c b/gcc/builtins.c
index 7d23469..39c0afb 100644
--- a/gcc/builtins.c
+++ b/gcc/builtins.c
@@ -5593,16 +5593,18 @@  expand_builtin_atomic_is_lock_free (tree exp)
 /* This routine will either emit the mem_thread_fence pattern or issue a 
    sync_synchronize to generate a fence for memory model MEMMODEL.  */
 
+#ifndef HAVE_mem_thread_fence
+# define HAVE_mem_thread_fence 0
+# define gen_mem_thread_fence(x) (gcc_unreachable (), NULL_RTX)
+#endif
+
 void
 expand_builtin_mem_thread_fence (enum memmodel model)
 {
-  if (model == MEMMODEL_RELAXED)
-    return;
-#ifdef HAVE_mem_thread_fence
-  emit_insn (gen_mem_thread_fence (GEN_INT (model)));
-#else
-  expand_builtin_sync_synchronize ();
-#endif
+  if (HAVE_mem_thread_fence)
+    emit_insn (gen_mem_thread_fence (GEN_INT (model)));
+  else if (model != MEMMODEL_RELAXED)
+    expand_builtin_sync_synchronize ();
 }
 
 /* Expand the __atomic_thread_fence intrinsic:
@@ -5621,15 +5623,37 @@  expand_builtin_atomic_thread_fence (tree exp)
 /* This routine will either emit the mem_signal_fence pattern or issue a 
    sync_synchronize to generate a fence for memory model MEMMODEL.  */
 
+#ifndef HAVE_mem_signal_fence
+# define HAVE_mem_signal_fence 0
+# define gen_mem_signal_fence(x) (gcc_unreachable (), NULL_RTX)
+#endif
+
 static void
 expand_builtin_mem_signal_fence (enum memmodel model)
 {
-#ifdef HAVE_mem_signal_fence
-  emit_insn (gen_mem_signal_fence (memmodel));
-#else
-  if (model != MEMMODEL_RELAXED)
-    expand_builtin_sync_synchronize ();
-#endif
+  if (HAVE_mem_signal_fence)
+    emit_insn (gen_mem_signal_fence (GEN_INT (model)));
+  else if (model != MEMMODEL_RELAXED)
+    {
+      rtx asm_op, clob;
+
+      /* By default targets are coherent between a thread and the signal
+	 handler running on the same thread.  Thus this really becomes a
+	 compiler barrier, in that stores must not be sunk past
+	 (or raised above) a given point.  */
+
+      /* Generate asm volatile("" : : : "memory") as the memory barrier.  */
+      asm_op = gen_rtx_ASM_OPERANDS (VOIDmode, empty_string, empty_string, 0,
+				     rtvec_alloc (0), rtvec_alloc (0),
+				     rtvec_alloc (0), UNKNOWN_LOCATION);
+      MEM_VOLATILE_P (asm_op) = 1;
+
+      clob = gen_rtx_SCRATCH (VOIDmode);
+      clob = gen_rtx_MEM (BLKmode, clob);
+      clob = gen_rtx_CLOBBER (VOIDmode, clob);
+
+      emit_insn (gen_rtx_PARALLEL (VOIDmode, gen_rtvec (2, asm_op, clob)));
+    }
 }
 
 /* Expand the __atomic_signal_fence intrinsic: