[PATCH 2/2][IRA,LRA] Fix PR86939, IRA incorrectly creates an interference between a pseudo register and a hard register

[Peter Bergner <bergner@linux.ibm.com>]

gcc/
	* ira.h (copy_insn_p): New prototype.
	* ira-lives.c (ignore_reg_for_conflicts): New static variable.
	(make_hard_regno_dead): Don't add conflicts for register
	ignore_reg_for_conflicts.
	(make_object_dead): Likewise.
	(copy_insn_p): New function.
	(process_bb_node_lives): Set ignore_reg_for_conflicts for copies.
	* lra-lives.c (ignore_reg_for_conflicts): New static variable.
	(make_hard_regno_dead): Don't add conflicts for register
	ignore_reg_for_conflicts.
	(mark_pseudo_dead): Likewise.
	(process_bb_lives): Set ignore_reg_for_conflicts for copies.

gcc/testsuite/
	* gcc.target/powerpc/pr86939.c: New test.

Index: gcc/ira.h
===================================================================
--- gcc/ira.h     (revision 263506)
+++ gcc/ira.h     (working copy)
@@ -210,6 +210,9 @@ extern void ira_adjust_equiv_reg_cost (u
 /* ira-costs.c */
 extern void ira_costs_c_finalize (void);
 
+/* ira-lives.c */
+extern rtx copy_insn_p (rtx_insn *);
+
 /* Spilling static chain pseudo may result in generation of wrong
    non-local goto code using frame-pointer to address saved stack
    pointer value after restoring old frame pointer value.  The
Index: gcc/ira-lives.c
===================================================================
--- gcc/ira-lives.c     (revision 263506)
+++ gcc/ira-lives.c     (working copy)
@@ -84,6 +84,10 @@ static int *allocno_saved_at_call;
    supplemental to recog_data.  */
 static alternative_mask preferred_alternatives;
 
+/* If non-NULL, the source operand of a register to register copy for which
+   we should not add a conflict with the copy's destination operand.  */
+static rtx ignore_reg_for_conflicts;
+
 /* Record hard register REGNO as now being live.  */
 static void
 make_hard_regno_live (int regno)
@@ -101,6 +105,11 @@ make_hard_regno_dead (int regno)
     {
       ira_object_t obj = ira_object_id_map[i];
 
+      if (ignore_reg_for_conflicts != NULL_RTX
+	  && REGNO (ignore_reg_for_conflicts)
+	     == (unsigned int) ALLOCNO_REGNO (OBJECT_ALLOCNO (obj)))
+	continue;
+
       SET_HARD_REG_BIT (OBJECT_CONFLICT_HARD_REGS (obj), regno);
       SET_HARD_REG_BIT (OBJECT_TOTAL_CONFLICT_HARD_REGS (obj), regno);
     }
@@ -154,12 +163,38 @@ static void
 make_object_dead (ira_object_t obj)
 {
   live_range_t lr;
+  int ignore_regno = -1;
+  int last_regno = -1;
 
   sparseset_clear_bit (objects_live, OBJECT_CONFLICT_ID (obj));
 
+  /* Check whether any part of IGNORE_REG_FOR_CONFLICTS already conflicts
+     with OBJ.  */
+  if (ignore_reg_for_conflicts != NULL_RTX
+      && REGNO (ignore_reg_for_conflicts) < FIRST_PSEUDO_REGISTER)
+    {
+      last_regno = END_REGNO (ignore_reg_for_conflicts);
+      int src_regno = ignore_regno = REGNO (ignore_reg_for_conflicts);
+
+      while (src_regno < last_regno)
+	{
+	  if (TEST_HARD_REG_BIT (OBJECT_CONFLICT_HARD_REGS (obj), src_regno))
+	    {
+	      ignore_regno = last_regno = -1;
+	      break;
+	    }
+	  src_regno++;
+	}
+    }
+
   IOR_HARD_REG_SET (OBJECT_CONFLICT_HARD_REGS (obj), hard_regs_live);
   IOR_HARD_REG_SET (OBJECT_TOTAL_CONFLICT_HARD_REGS (obj), hard_regs_live);
 
+  /* If IGNORE_REG_FOR_CONFLICTS did not already conflict with OBJ, make
+     sure it still doesn't.  */
+  for (; ignore_regno < last_regno; ignore_regno++)
+    CLEAR_HARD_REG_BIT (OBJECT_CONFLICT_HARD_REGS (obj), ignore_regno);
+
   lr = OBJECT_LIVE_RANGES (obj);
   ira_assert (lr != NULL);
   lr->finish = curr_point;
@@ -1022,6 +1057,38 @@ find_call_crossed_cheap_reg (rtx_insn *i
   return cheap_reg;
 }  
 
+/* Determine whether INSN is a register to register copy of the type where
+   we do not need to make the source and destiniation registers conflict.
+   If this is a copy instruction, then return the source reg.  Otherwise,
+   return NULL_RTX.  */
+rtx
+copy_insn_p (rtx_insn *insn)
+{
+  rtx set;
+
+  /* Disallow anything other than a simple register to register copy
+     that has no side effects.  */
+  if ((set = single_set (insn)) == NULL_RTX
+      || !REG_P (SET_DEST (set))
+      || !REG_P (SET_SRC (set))
+      || side_effects_p (set))
+    return NULL_RTX;
+
+  int dst_regno = REGNO (SET_DEST (set));
+  int src_regno = REGNO (SET_SRC (set));
+  machine_mode mode = GET_MODE (SET_DEST (set));
+
+  /* Computing conflicts for register pairs is difficult to get right, so
+     for now, disallow it.  */
+  if ((dst_regno < FIRST_PSEUDO_REGISTER
+       && hard_regno_nregs (dst_regno, mode) != 1)
+      || (src_regno < FIRST_PSEUDO_REGISTER
+	  && hard_regno_nregs (src_regno, mode) != 1))
+    return NULL_RTX;
+
+  return SET_SRC (set);
+}
+
 /* Process insns of the basic block given by its LOOP_TREE_NODE to
    update allocno live ranges, allocno hard register conflicts,
    intersected calls, and register pressure info for allocnos for the
@@ -1107,6 +1174,7 @@ process_bb_node_lives (ira_loop_tree_nod
 		     curr_point);
 
 	  call_p = CALL_P (insn);
+	  ignore_reg_for_conflicts = copy_insn_p (insn);
 #ifdef REAL_PIC_OFFSET_TABLE_REGNUM
 	  int regno;
 	  bool clear_pic_use_conflict_p = false;
@@ -1289,6 +1357,7 @@ process_bb_node_lives (ira_loop_tree_nod
 #endif
 	  curr_point++;
 	}
+      ignore_reg_for_conflicts = NULL_RTX;
 
       if (bb_has_eh_pred (bb))
 	for (j = 0; ; ++j)
Index: gcc/ira-lives.c
===================================================================
--- gcc/lra-lives.c     (revision 263506)
+++ gcc/lra-lives.c     (working copy)
@@ -96,6 +96,10 @@ static bitmap_head temp_bitmap;
 /* Pool for pseudo live ranges.	 */
 static object_allocator<lra_live_range> lra_live_range_pool ("live ranges");
 
+/* If non-NULL, the source operand of a register to register copy for which
+   we should not add a conflict with the copy's destination operand.  */
+static rtx ignore_reg_for_conflicts;
+
 /* Free live range list LR.  */
 static void
 free_live_range_list (lra_live_range_t lr)
@@ -251,13 +255,18 @@ make_hard_regno_dead (int regno, bool ch
   sparseset_set_bit (start_dying, regno);
   unsigned int i;
   EXECUTE_IF_SET_IN_SPARSESET (pseudos_live, i)
+    {
+      if (ignore_reg_for_conflicts != NULL_RTX
+	  && REGNO (ignore_reg_for_conflicts) == i)
+	continue;
 #ifdef REAL_PIC_OFFSET_TABLE_REGNUM
-    if (! check_pic_pseudo_p
-	|| regno != REAL_PIC_OFFSET_TABLE_REGNUM
-	|| pic_offset_table_rtx == NULL
-	|| i != REGNO (pic_offset_table_rtx))
+      if (! check_pic_pseudo_p
+	  || regno != REAL_PIC_OFFSET_TABLE_REGNUM
+	  || pic_offset_table_rtx == NULL
+	  || i != REGNO (pic_offset_table_rtx))
 #endif
-      SET_HARD_REG_BIT (lra_reg_info[i].conflict_hard_regs, regno);
+	SET_HARD_REG_BIT (lra_reg_info[i].conflict_hard_regs, regno);
+    }
   CLEAR_HARD_REG_BIT (hard_regs_live, regno);
   if (fixed_regs[regno] || TEST_HARD_REG_BIT (hard_regs_spilled_into, regno))
     {
@@ -294,14 +303,41 @@ static void
 mark_pseudo_dead (int regno, int point)
 {
   lra_live_range_t p;
+  int ignore_regno = -1;
+  int last_regno = -1;
 
   lra_assert (regno >= FIRST_PSEUDO_REGISTER);
   lra_assert (sparseset_bit_p (pseudos_live, regno));
   sparseset_clear_bit (pseudos_live, regno);
   sparseset_set_bit (start_dying, regno);
 
+  /* Check whether any part of IGNORE_REG_FOR_CONFLICTS already conflicts
+     with REGNO.  */
+  if (ignore_reg_for_conflicts != NULL_RTX
+      && REGNO (ignore_reg_for_conflicts) < FIRST_PSEUDO_REGISTER)
+    {
+      last_regno = END_REGNO (ignore_reg_for_conflicts);
+      int src_regno = ignore_regno = REGNO (ignore_reg_for_conflicts);
+
+      while (src_regno < last_regno)
+	{
+	  if (TEST_HARD_REG_BIT (lra_reg_info[regno].conflict_hard_regs,
+				 src_regno))
+	    {
+	      ignore_regno = last_regno = -1;
+	      break;
+	    }
+	  src_regno++;
+	}
+    }
+
   IOR_HARD_REG_SET (lra_reg_info[regno].conflict_hard_regs, hard_regs_live);
 
+  /* If IGNORE_REG_FOR_CONFLICTS did not already conflict with REGNO, make
+     sure it still doesn't.  */
+  for (; ignore_regno < last_regno; ignore_regno++)
+    CLEAR_HARD_REG_BIT (lra_reg_info[regno].conflict_hard_regs, ignore_regno);
+
   if (complete_info_p || lra_get_regno_hard_regno (regno) < 0)
     {
       p = lra_reg_info[regno].live_ranges;
@@ -747,6 +783,7 @@ process_bb_lives (basic_block bb, int &c
 	}
 
       call_p = CALL_P (curr_insn);
+      ignore_reg_for_conflicts = copy_insn_p (curr_insn);
       src_regno = (set != NULL_RTX && REG_P (SET_SRC (set))
 		   ? REGNO (SET_SRC (set)) : -1);
       dst_regno = (set != NULL_RTX && REG_P (SET_DEST (set))
@@ -989,6 +1026,7 @@ process_bb_lives (basic_block bb, int &c
       EXECUTE_IF_SET_IN_SPARSESET (unused_set, j)
 	add_reg_note (curr_insn, REG_UNUSED, regno_reg_rtx[j]);
     }
+  ignore_reg_for_conflicts = NULL_RTX;
 
   if (bb_has_eh_pred (bb))
     for (j = 0; ; ++j)
Index: gcc/testsuite/gcc.target/powerpc/pr86939.c
===================================================================
--- gcc/testsuite/gcc.target/powerpc/pr86939.c	(nonexistent)
+++ gcc/testsuite/gcc.target/powerpc/pr86939.c	(working copy)
@@ -0,0 +1,12 @@
+/* { dg-do compile { target { powerpc*-*-* } } } */
+/* { dg-options "-O2" } */
+
+typedef long (*fptr_t) (void);
+long
+func (fptr_t *p)
+{
+  if (p)
+    return (*p) ();
+  return 0;
+}
+/* { dg-final { scan-assembler-not {mr %?r?12,} } } */