[PATCH] S/390: Add static OSC breaker if necessary.

[Andreas Krebbel <krebbel at linux dot vnet dot ibm dot com>]

This patch adds a magic OSC (operand store compare) break instruction
which is necessary if a store is followed closely by a load with same
base+indx+displ while either base or index get modified in between.

The patch improves several SpecCPU testcases running on IBM z13.

I'll wait a few days for comments before committing the patch.

Bye,

-Andreas-

gcc/testsuite/ChangeLog:

2016-10-14  Andreas Krebbel  <krebbel@linux.vnet.ibm.com>

	* gcc.target/s390/oscbreak-1.c: New test.

gcc/ChangeLog:

2016-10-14  Andreas Krebbel  <krebbel@linux.vnet.ibm.com>

	* config/s390/s390.c (s390_adjust_loop_scan_osc): New function.
	(s390_adjust_loops): New function.
	(s390_reorg): Invoke s390_adjust_loops.
	* config/s390/s390.md: (UNSPEC_OSC_BREAK): New constant.
	("osc_break"): New insn definition.
---
 gcc/config/s390/s390.c                     | 152 +++++++++++++++++++++++++++++
 gcc/config/s390/s390.md                    |   8 ++
 gcc/testsuite/gcc.target/s390/oscbreak-1.c |  25 +++++
 3 files changed, 185 insertions(+)
 create mode 100644 gcc/testsuite/gcc.target/s390/oscbreak-1.c

diff --git a/gcc/config/s390/s390.c b/gcc/config/s390/s390.c
index f69b470..3554f33 100644
--- a/gcc/config/s390/s390.c
+++ b/gcc/config/s390/s390.c
@@ -13502,6 +13502,155 @@ s390_z10_optimize_cmp (rtx_insn *insn)
   return insn_added_p;
 }
 
+/* Number of INSNs to be scanned backward in the last BB of the loop
+   and forward in the first BB of the loop.  This usually should be a
+   bit more than the number of INSNs which could go into one
+   group.  */
+#define S390_OSC_SCAN_INSN_NUM 5
+
+/* Scan LOOP for static OSC collisions and return true if a osc_break
+   should be issued for this loop.  */
+static bool
+s390_adjust_loop_scan_osc (struct loop* loop)
+
+{
+  HARD_REG_SET modregs, newregs;
+  rtx_insn *insn, *store_insn = NULL;
+  rtx set;
+  struct s390_address addr_store, addr_load;
+  subrtx_iterator::array_type array;
+  int insn_count;
+
+  CLEAR_HARD_REG_SET (modregs);
+
+  insn_count = 0;
+  FOR_BB_INSNS_REVERSE (loop->latch, insn)
+    {
+      if (!INSN_P (insn) || INSN_CODE (insn) <= 0)
+	continue;
+
+      insn_count++;
+      if (insn_count > S390_OSC_SCAN_INSN_NUM)
+	return false;
+
+      find_all_hard_reg_sets (insn, &newregs, true);
+      IOR_HARD_REG_SET (modregs, newregs);
+
+      set = single_set (insn);
+      if (!set)
+	continue;
+
+      if (MEM_P (SET_DEST (set))
+	  && s390_decompose_address (XEXP (SET_DEST (set), 0), &addr_store))
+	{
+	  store_insn = insn;
+	  break;
+	}
+    }
+
+  if (store_insn == NULL_RTX)
+    return false;
+
+  insn_count = 0;
+  FOR_BB_INSNS (loop->header, insn)
+    {
+      if (!INSN_P (insn) || INSN_CODE (insn) <= 0)
+	continue;
+
+      if (insn == store_insn)
+	return false;
+
+      insn_count++;
+      if (insn_count > S390_OSC_SCAN_INSN_NUM)
+	return false;
+
+      find_all_hard_reg_sets (insn, &newregs, true);
+      IOR_HARD_REG_SET (modregs, newregs);
+
+      set = single_set (insn);
+      if (!set)
+	continue;
+
+      /* An intermediate store disrupts static OSC checking
+	 anyway.  */
+      if (MEM_P (SET_DEST (set))
+	  && s390_decompose_address (XEXP (SET_DEST (set), 0), NULL))
+	return false;
+
+      FOR_EACH_SUBRTX (iter, array, SET_SRC (set), NONCONST)
+	if (MEM_P (*iter)
+	    && s390_decompose_address (XEXP (*iter, 0), &addr_load)
+	    && rtx_equal_p (addr_load.base, addr_store.base)
+	    && rtx_equal_p (addr_load.indx, addr_store.indx)
+	    && rtx_equal_p (addr_load.disp, addr_store.disp))
+	  {
+	    if ((addr_load.base != NULL_RTX
+		 && TEST_HARD_REG_BIT (modregs, REGNO (addr_load.base)))
+		|| (addr_load.indx != NULL_RTX
+		    && TEST_HARD_REG_BIT (modregs, REGNO (addr_load.indx))))
+	      return true;
+	  }
+    }
+  return false;
+}
+
+/* Look for adjustments which can be done on simple innermost
+   loops.  */
+static void
+s390_adjust_loops ()
+{
+  struct loop *loop = NULL;
+
+  df_analyze ();
+  compute_bb_for_insn ();
+
+  /* Find the loops.  */
+  loop_optimizer_init (AVOID_CFG_MODIFICATIONS);
+
+  FOR_EACH_LOOP (loop, LI_ONLY_INNERMOST)
+    {
+      if (dump_file)
+	{
+	  flow_loop_dump (loop, dump_file, NULL, 0);
+	  fprintf (dump_file, ";;  OSC loop scan Loop: ");
+	}
+      if (loop->latch == NULL
+	  || pc_set (BB_END (loop->latch)) == NULL_RTX
+	  || !s390_adjust_loop_scan_osc (loop))
+	{
+	  if (dump_file)
+	    {
+	      if (loop->latch == NULL)
+		fprintf (dump_file, " muliple backward jumps\n");
+	      else
+		{
+		  fprintf (dump_file, " header insn: %d latch insn: %d ",
+			   INSN_UID (BB_HEAD (loop->header)),
+			   INSN_UID (BB_END (loop->latch)));
+		  if (pc_set (BB_END (loop->latch)) == NULL_RTX)
+		    fprintf (dump_file, " loop does not end with jump\n");
+		  else
+		    fprintf (dump_file, " not instrumented\n");
+		}
+	    }
+	}
+      else
+	{
+	  rtx_insn *new_insn;
+
+	  if (dump_file)
+	    fprintf (dump_file, " adding OSC break insn: ");
+	  new_insn = emit_insn_before (gen_osc_break (),
+				       BB_END (loop->latch));
+	  INSN_ADDRESSES_NEW (new_insn, -1);
+	}
+    }
+
+  loop_optimizer_finalize ();
+
+  df_finish_pass (false);
+}
+
 /* Perform machine-dependent processing.  */
 
 static void
@@ -13510,6 +13659,9 @@ s390_reorg (void)
   bool pool_overflow = false;
   int hw_before, hw_after;
 
+  if (s390_tune == PROCESSOR_2964_Z13)
+    s390_adjust_loops ();
+
   /* Make sure all splits have been performed; splits after
      machine_dependent_reorg might confuse insn length counts.  */
   split_all_insns_noflow ();
diff --git a/gcc/config/s390/s390.md b/gcc/config/s390/s390.md
index 9de442f..d97a811 100644
--- a/gcc/config/s390/s390.md
+++ b/gcc/config/s390/s390.md
@@ -280,6 +280,8 @@
    ; Split stack support
    UNSPECV_SPLIT_STACK_CALL
    UNSPECV_SPLIT_STACK_DATA
+
+   UNSPECV_OSC_BREAK
   ])
 
 ;;
@@ -11196,3 +11198,9 @@
   "jg%C1\t%0"
   [(set_attr "op_type" "RIL")
    (set_attr "type"  "branch")])
+
+(define_insn "osc_break"
+  [(unspec_volatile [(const_int 0)] UNSPECV_OSC_BREAK)]
+  ""
+  "bcr\t7,%%r0"
+  [(set_attr "op_type" "RR")])
diff --git a/gcc/testsuite/gcc.target/s390/oscbreak-1.c b/gcc/testsuite/gcc.target/s390/oscbreak-1.c
new file mode 100644
index 0000000..fdf356c
--- /dev/null
+++ b/gcc/testsuite/gcc.target/s390/oscbreak-1.c
@@ -0,0 +1,25 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -mtune=z13 -dp" } */
+
+void
+foo (char *a, int b)
+{
+  int i;
+
+  for (i = 0; i < b; i++)
+    a[i] += 1;
+}
+
+void
+bar (char *a, int b)
+{
+  int i;
+
+  for (i = 0; i < b; i++)
+    {
+      if (a[i] & 1)
+	a[i] = 1;
+    }
+}
+
+/* { dg-final { scan-assembler "osc_break" } } */
-- 
2.9.1