ira.c validate_equiv_mem

This function is used to validate REG_EQUIV notes generated by ira,
and to validate potential insn combines performed by ira.  The two
conditions are not exactly the same, with reload being more
restrictive.  Separate them so more combines/moves can occur.

For example, this sequence from cfgexpand.c:expand_gimple_cond
	callq  _Z18update_bb_for_insnP15basic_block_def
	mov    0x10(%rbx),%rdi
	mov    0x0(%rip),%rbp        # x_rtl+0x34
	callq  _Z9safe_as_aIP8rtx_insn7rtx_defET_PT0_
	mov    %r13,%rdx
	mov    %rbp,%rsi
	mov    %rax,%rdi
	callq  _Z18create_basic_blockP7rtx_defS0_P15basic_block_def

becomes
	callq  _Z18update_bb_for_insnP15basic_block_def
	mov    0x10(%rbx),%rdi
	callq  _Z9safe_as_aIP8rtx_insn7rtx_defET_PT0_
	mov    0x0(%rip),%rsi        # x_rtl+0x34
	mov    %r13,%rdx
	mov    %rax,%rdi
	callq  _Z18create_basic_blockP7rtx_defS0_P15basic_block_def

	* ira.c (enum valid_equiv): New.
	(validate_equiv_mem): Return enum.
	(update_equiv_mem): Create replacement in more cases.
	(add_store_equivs): Update validate_equiv_mem call.

From-SVN: r235661

gcc/ChangeLog

 2016-04-30  Alan Modra  <amodra@gmail.com>
 
+	* ira.c (enum valid_equiv): New.
+	(validate_equiv_mem): Return enum.
+	(update_equiv_mem): Create replacement in more cases.
+	(add_store_equivs): Update validate_equiv_mem call.
+
+2016-04-30  Alan Modra  <amodra@gmail.com>
+
 	* ira.c (combine_and_move_insns): Rather than scanning insns,
 	use DF infrastucture to find use and def insns.
 

gcc/ira.c

@@ -2951,43 +2951,56 @@ validate_equiv_mem_from_store (rtx dest, const_rtx set ATTRIBUTE_UNUSED,
     info->equiv_mem_modified = true;
 }
 
+enum valid_equiv { valid_none, valid_combine, valid_reload };
+
 /* Verify that no store between START and the death of REG invalidates
    MEMREF.  MEMREF is invalidated by modifying a register used in MEMREF,
    by storing into an overlapping memory location, or with a non-const
    CALL_INSN.
 
-   Return 1 if MEMREF remains valid.  */
-static int
+   Return VALID_RELOAD if MEMREF remains valid for both reload and
+   combine_and_move insns, VALID_COMBINE if only valid for
+   combine_and_move_insns, and VALID_NONE otherwise.  */
+static enum valid_equiv
 validate_equiv_mem (rtx_insn *start, rtx reg, rtx memref)
 {
   rtx_insn *insn;
   rtx note;
   struct equiv_mem_data info = { memref, false };
+  enum valid_equiv ret = valid_reload;
 
   /* If the memory reference has side effects or is volatile, it isn't a
      valid equivalence.  */
   if (side_effects_p (memref))
-    return 0;
+    return valid_none;
 
   for (insn = start; insn; insn = NEXT_INSN (insn))
     {
-      if (! INSN_P (insn))
+      if (!INSN_P (insn))
 	continue;
 
       if (find_reg_note (insn, REG_DEAD, reg))
-	return 1;
+	return ret;
 
-      /* This used to ignore readonly memory and const/pure calls.  The problem
-	 is the equivalent form may reference a pseudo which gets assigned a
-	 call clobbered hard reg.  When we later replace REG with its
-	 equivalent form, the value in the call-clobbered reg has been
-	 changed and all hell breaks loose.  */
       if (CALL_P (insn))
-	return 0;
+	{
+	  /* We can combine a reg def from one insn into a reg use in
+	     another over a call if the memory is readonly or the call
+	     const/pure.  However, we can't set reg_equiv notes up for
+	     reload over any call.  The problem is the equivalent form
+	     may reference a pseudo which gets assigned a call
+	     clobbered hard reg.  When we later replace REG with its
+	     equivalent form, the value in the call-clobbered reg has
+	     been changed and all hell breaks loose.  */
+	  ret = valid_combine;
+	  if (!MEM_READONLY_P (memref)
+	      && !RTL_CONST_OR_PURE_CALL_P (insn))
+	    return valid_none;
+	}
 
       note_stores (PATTERN (insn), validate_equiv_mem_from_store, &info);
       if (info.equiv_mem_modified)
-	return 0;
+	return valid_none;
 
       /* If a register mentioned in MEMREF is modified via an
 	 auto-increment, we lose the equivalence.  Do the same if one
@@ -2999,10 +3012,10 @@ validate_equiv_mem (rtx_insn *start, rtx reg, rtx memref)
 	     || REG_NOTE_KIND (note) == REG_DEAD)
 	    && REG_P (XEXP (note, 0))
 	    && reg_overlap_mentioned_p (XEXP (note, 0), memref))
-	  return 0;
+	  return valid_none;
     }
 
-  return 0;
+  return valid_none;
 }
 
 /* Returns zero if X is known to be invariant.  */
@@ -3510,24 +3523,32 @@ update_equiv_regs (void)
 	     note.  */
 	  note = find_reg_note (insn, REG_EQUIV, NULL_RTX);
 
-	  if (note == NULL_RTX && REG_BASIC_BLOCK (regno) >= NUM_FIXED_BLOCKS
-	      && MEM_P (SET_SRC (set))
-	      && validate_equiv_mem (insn, dest, SET_SRC (set)))
-	    note = set_unique_reg_note (insn, REG_EQUIV, copy_rtx (SET_SRC (set)));
-
+	  rtx replacement = NULL_RTX;
 	  if (note)
+	    replacement = XEXP (note, 0);
+	  else if (REG_BASIC_BLOCK (regno) >= NUM_FIXED_BLOCKS
+		   && MEM_P (SET_SRC (set)))
 	    {
-	      int regno = REGNO (dest);
-	      rtx x = XEXP (note, 0);
+	      enum valid_equiv validity;
+	      validity = validate_equiv_mem (insn, dest, SET_SRC (set));
+	      if (validity != valid_none)
+		{
+		  replacement = copy_rtx (SET_SRC (set));
+		  if (validity == valid_reload)
+		    note = set_unique_reg_note (insn, REG_EQUIV, replacement);
+		}
+	    }
 
-	      /* If we haven't done so, record for reload that this is an
-		 equivalencing insn.  */
-	      if (!reg_equiv[regno].is_arg_equivalence)
-		ira_reg_equiv[regno].init_insns
-		  = gen_rtx_INSN_LIST (VOIDmode, insn,
-				       ira_reg_equiv[regno].init_insns);
+	  /* If we haven't done so, record for reload that this is an
+	     equivalencing insn.  */
+	  if (note && !reg_equiv[regno].is_arg_equivalence)
+	    ira_reg_equiv[regno].init_insns
+	      = gen_rtx_INSN_LIST (VOIDmode, insn,
+				   ira_reg_equiv[regno].init_insns);
 
-	      reg_equiv[regno].replacement = x;
+	  if (replacement)
+	    {
+	      reg_equiv[regno].replacement = replacement;
 	      reg_equiv[regno].src_p = &SET_SRC (set);
 	      reg_equiv[regno].loop_depth = (short) loop_depth;
 
@@ -3548,7 +3569,7 @@ update_equiv_regs (void)
 		     calls.  */
 
 		  if (REG_N_REFS (regno) == 2
-		      && (rtx_equal_p (x, src)
+		      && (rtx_equal_p (replacement, src)
 			  || ! equiv_init_varies_p (src))
 		      && NONJUMP_INSN_P (insn)
 		      && equiv_init_movable_p (PATTERN (insn), regno))
@@ -3599,7 +3620,7 @@ add_store_equivs (void)
 	  && (init_insn = reg_equiv[regno].init_insns->insn ()) != 0
 	  && bitmap_bit_p (&seen_insns, INSN_UID (init_insn))
 	  && ! find_reg_note (init_insn, REG_EQUIV, NULL_RTX)
-	  && validate_equiv_mem (init_insn, src, dest)
+	  && validate_equiv_mem (init_insn, src, dest) == valid_reload
 	  && ! memref_used_between_p (dest, init_insn, insn)
 	  /* Attaching a REG_EQUIV note will fail if INIT_INSN has
 	     multiple sets.  */