[nvptx] Add workaround for subsequent bar.syncs

2018-05-05  Tom de Vries  <tom@codesourcery.com>

	PR target/85653
	* config/nvptx/nvptx.c (WORKAROUND_PTXJIT_BUG_3): Define.
	(workaround_barsyncs): New function.
	(nvptx_reorg): Use workaround_barsyncs.
	* config/nvptx/nvptx.md (define_c_enum "unspecv"): Add UNSPECV_MEMBAR.
	(define_expand "nvptx_membar_cta"): New define_expand.
	(define_insn "*nvptx_membar_cta"): New insn.

From-SVN: r259967

gcc/ChangeLog

+2018-05-05  Tom de Vries  <tom@codesourcery.com>
+
+	PR target/85653
+	* config/nvptx/nvptx.c (WORKAROUND_PTXJIT_BUG_3): Define.
+	(workaround_barsyncs): New function.
+	(nvptx_reorg): Use workaround_barsyncs.
+	* config/nvptx/nvptx.md (define_c_enum "unspecv"): Add UNSPECV_MEMBAR.
+	(define_expand "nvptx_membar_cta"): New define_expand.
+	(define_insn "*nvptx_membar_cta"): New insn.
+
 2018-05-04  Pekka Jääskeläinen  <pekka.jaaskelainen@parmance.com>
 
 	* brig-builtins.def: Add consts to ptrs etc. in BRIG builtin defs.

gcc/config/nvptx/nvptx.c

@@ -79,6 +79,7 @@
 
 #define WORKAROUND_PTXJIT_BUG 1
 #define WORKAROUND_PTXJIT_BUG_2 1
+#define WORKAROUND_PTXJIT_BUG_3 1
 
 /* The various PTX memory areas an object might reside in.  */
 enum nvptx_data_area
@@ -4647,6 +4648,50 @@ prevent_branch_around_nothing (void)
   }
 #endif
 
+#ifdef WORKAROUND_PTXJIT_BUG_3
+/* Insert two membar.cta insns inbetween two subsequent bar.sync insns.  This
+   works around a hang observed at driver version 390.48 for sm_50.  */
+
+static void
+workaround_barsyncs (void)
+{
+  bool seen_barsync = false;
+  for (rtx_insn *insn = get_insns (); insn; insn = NEXT_INSN (insn))
+    {
+      if (INSN_P (insn) && recog_memoized (insn) == CODE_FOR_nvptx_barsync)
+	{
+	  if (seen_barsync)
+	    {
+	      emit_insn_before (gen_nvptx_membar_cta (), insn);
+	      emit_insn_before (gen_nvptx_membar_cta (), insn);
+	    }
+
+	  seen_barsync = true;
+	  continue;
+	}
+
+      if (!seen_barsync)
+	continue;
+
+      if (NOTE_P (insn) || DEBUG_INSN_P (insn))
+	continue;
+      else if (INSN_P (insn))
+	switch (recog_memoized (insn))
+	  {
+	  case CODE_FOR_nvptx_fork:
+	  case CODE_FOR_nvptx_forked:
+	  case CODE_FOR_nvptx_joining:
+	  case CODE_FOR_nvptx_join:
+	    continue;
+	  default:
+	    break;
+	  }
+
+      seen_barsync = false;
+    }
+}
+#endif
+
 /* PTX-specific reorganization
    - Split blocks at fork and join instructions
    - Compute live registers
@@ -4730,6 +4775,10 @@ nvptx_reorg (void)
   prevent_branch_around_nothing ();
 #endif
 
+#ifdef WORKAROUND_PTXJIT_BUG_3
+  workaround_barsyncs ();
+#endif
+
   regstat_free_n_sets_and_refs ();
 
   df_finish_pass (true);

gcc/config/nvptx/nvptx.md

@@ -56,6 +56,7 @@
    UNSPECV_XCHG
    UNSPECV_BARSYNC
    UNSPECV_MEMBAR
+   UNSPECV_MEMBAR_CTA
    UNSPECV_DIM_POS
 
    UNSPECV_FORK
@@ -1481,6 +1482,22 @@
   "\\tmembar.sys;"
   [(set_attr "predicable" "false")])
 
+(define_expand "nvptx_membar_cta"
+  [(set (match_dup 0)
+	(unspec_volatile:BLK [(match_dup 0)] UNSPECV_MEMBAR_CTA))]
+  ""
+{
+  operands[0] = gen_rtx_MEM (BLKmode, gen_rtx_SCRATCH (Pmode));
+  MEM_VOLATILE_P (operands[0]) = 1;
+})
+
+(define_insn "*nvptx_membar_cta"
+  [(set (match_operand:BLK 0 "" "")
+	(unspec_volatile:BLK [(match_dup 0)] UNSPECV_MEMBAR_CTA))]
+  ""
+  "\\tmembar.cta;"
+  [(set_attr "predicable" "false")])
+
 (define_insn "nvptx_nounroll"
   [(unspec_volatile [(const_int 0)] UNSPECV_NOUNROLL)]
   ""