C6X port 5/11: Track predication conditions more accurately

[Bernd Schmidt <bernds@codesourcery.com>]

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The scheduler knows that insns with different COND_EXEC conditions don't
conflict and can be scheduled independently. Unfortunately, sched-deps.c
does not try to keep the conditions valid as it progresses. For example,

[B0] A0 = [A1]
     B0 = something
[!B0] [A2] = A0

The first and third insns have opposite conditions, so the scheduler
decides they are independent. For most targets this isn't a problem, as
the insn in the middle will produce enough dependencies to ensure the
right order. However, on C6X, order alone isn't sufficient due to the
exposed pipeline: we also need to ensure that the latencies are observed.


Bernd

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	* sched-int.h (struct _haifa_deps_insn_data): New members cond
	and reverse_cond.
	(INSN_COND, INSN_REVERSE_COND): New macros.
	* sched-deps.c (deps_analyze_insn): Call sched_get_condition_with_rev
	once.
	(sched_get_condition_with_rev): Cache the results, and look them up
	if possible.
	(sched_analyze_insn): Destroy INSN_COND of previous insns if they
	are clobbered by the current insn.

Index: gcc/sched-deps.c
===================================================================
--- gcc.orig/sched-deps.c
+++ gcc/sched-deps.c
@@ -489,13 +489,27 @@ deps_may_trap_p (const_rtx mem)
 
 /* Find the condition under which INSN is executed.  If REV is not NULL,
    it is set to TRUE when the returned comparison should be reversed
-   to get the actual condition.  */
+   to get the actual condition.
+   We only do actual work the first time we come here for an insn; the
+   results are cached in INSN_COND and INSN_REVERSE_COND.  */
 static rtx
 sched_get_condition_with_rev (const_rtx insn, bool *rev)
 {
   rtx pat = PATTERN (insn);
   rtx src;
 
+  if (INSN_COND (insn) == const_true_rtx)
+    return NULL_RTX;
+
+  if (INSN_COND (insn) != NULL_RTX)
+    {
+      if (rev)
+	*rev = INSN_REVERSE_COND (insn);
+      return INSN_COND (insn);
+    }
+
+  INSN_COND (insn) = const_true_rtx;
+  INSN_REVERSE_COND (insn) = false;
   if (pat == 0)
     return 0;
 
@@ -503,7 +517,10 @@ sched_get_condition_with_rev (const_rtx
     *rev = false;
 
   if (GET_CODE (pat) == COND_EXEC)
-    return COND_EXEC_TEST (pat);
+    {
+      INSN_COND (insn) = COND_EXEC_TEST (pat);
+      return COND_EXEC_TEST (pat);
+    }
 
   if (!any_condjump_p (insn) || !onlyjump_p (insn))
     return 0;
@@ -511,7 +528,10 @@ sched_get_condition_with_rev (const_rtx
   src = SET_SRC (pc_set (insn));
 
   if (XEXP (src, 2) == pc_rtx)
-    return XEXP (src, 0);
+    {
+      INSN_COND (insn) = XEXP (src, 0);
+      return XEXP (src, 0);
+    }
   else if (XEXP (src, 1) == pc_rtx)
     {
       rtx cond = XEXP (src, 0);
@@ -522,6 +542,8 @@ sched_get_condition_with_rev (const_rtx
 
       if (rev)
 	*rev = true;
+      INSN_COND (insn) = cond;
+      INSN_REVERSE_COND (insn) = true;
       return cond;
     }
 
@@ -2841,6 +2863,8 @@ sched_analyze_insn (struct deps_desc *de
     }
   else
     {
+      regset_head set_or_clobbered;
+
       EXECUTE_IF_SET_IN_REG_SET (reg_pending_uses, 0, i, rsi)
 	{
 	  struct deps_reg *reg_last = &deps->reg_last[i];
@@ -2871,6 +2895,21 @@ sched_analyze_insn (struct deps_desc *de
 	      }
 	  }
 
+      INIT_REG_SET (&set_or_clobbered);
+      bitmap_ior (&set_or_clobbered, reg_pending_clobbers, reg_pending_sets);
+      EXECUTE_IF_SET_IN_REG_SET (&set_or_clobbered, 0, i, rsi)
+	{
+	  struct deps_reg *reg_last = &deps->reg_last[i];
+	  rtx list;
+	  for (list = reg_last->uses; list; list = XEXP (list, 1))
+	    {
+	      rtx other = XEXP (list, 0);
+	      if (INSN_COND (other) != const_true_rtx
+		  && refers_to_regno_p (i, i + 1, INSN_COND (other), NULL))
+		INSN_COND (other) = const_true_rtx;
+	    }
+	}
+
       /* If the current insn is conditional, we can't free any
 	 of the lists.  */
       if (sched_has_condition_p (insn))
@@ -3245,6 +3284,10 @@ deps_analyze_insn (struct deps_desc *dep
   if (sched_deps_info->start_insn)
     sched_deps_info->start_insn (insn);
 
+  /* Record the condition for this insn.  */
+  if (NONDEBUG_INSN_P (insn))
+    sched_get_condition_with_rev (insn, NULL);
+
   if (NONJUMP_INSN_P (insn) || DEBUG_INSN_P (insn) || JUMP_P (insn))
     {
       /* Make each JUMP_INSN (but not a speculative check)
Index: gcc/sched-int.h
===================================================================
--- gcc.orig/sched-int.h
+++ gcc/sched-int.h
@@ -716,6 +716,17 @@ struct _haifa_deps_insn_data
      search in 'forw_deps'.  */
   deps_list_t resolved_forw_deps;
 
+  /* If the insn is conditional (either through COND_EXEC, or because
+     it is a conditional branch), this records the condition.  NULL
+     for insns that haven't been seen yet or don't have a condition;
+     const_true_rtx to mark an insn without a condition, or with a
+     condition that has been clobbered by a subsequent insn.  */
+  rtx cond;
+
+  /* True if the condition in 'cond' should be reversed to get the actual
+     condition.  */
+  unsigned int reverse_cond : 1;
+
   /* Some insns (e.g. call) are not allowed to move across blocks.  */
   unsigned int cant_move : 1;
 };
@@ -891,6 +902,8 @@ extern VEC(haifa_deps_insn_data_def, hea
 #define INSN_RESOLVED_FORW_DEPS(INSN) (HDID (INSN)->resolved_forw_deps)
 #define INSN_HARD_BACK_DEPS(INSN) (HDID (INSN)->hard_back_deps)
 #define INSN_SPEC_BACK_DEPS(INSN) (HDID (INSN)->spec_back_deps)
+#define INSN_COND(INSN)	(HDID (INSN)->cond)
+#define INSN_REVERSE_COND(INSN) (HDID (INSN)->reverse_cond)
 #define CANT_MOVE(INSN)	(HDID (INSN)->cant_move)
 #define CANT_MOVE_BY_LUID(LUID)	(VEC_index (haifa_deps_insn_data_def, h_d_i_d, \
                                             LUID)->cant_move)