Re: [RFC] Fix PR rtl-optimization/33732

[Rask Ingemann Lambertsen <rask at sygehus dot dk>]

On Wed, Nov 07, 2007 at 09:35:32PM +0100, Rask Ingemann Lambertsen wrote:
>    This happens because in df-scan.c at line 2676 (df_ref_record()) we have
> 
>       for (i = regno; i < endregno; i++)
>         {
>           ref = df_ref_create_structure (collection_rec, regno_reg_rtx[i], loc,
>                                          bb, insn, ref_type, ref_flags);
> 
> with regno = 22 and endregno = 23 with loc pointing to the
> (subreg:SI (reg:DI 21) 4) expression. df_ref_create_structure() will then set
> DF_REF_REG(ref) to regno_reg_rtx[22] and point DF_REF_LOC(ref) to the
> (subreg:SI (reg:DI 21) 4) expression. This goes wrong in df-problems.c at line 2832
> (df_note_bb_compute()), where we have
> 
>                   rtx reg = (DF_REF_LOC (use))
>                             ? *DF_REF_REAL_LOC (use) : DF_REF_REG (use);
>                   old_dead_notes = df_set_note (REG_DEAD, insn, old_dead_notes, reg);
> 
> #ifdef REG_DEAD_DEBUGGING
>                   df_print_note ("adding 4: ", insn, REG_NOTES (insn));
> 
> and so dig into the subreg expression and find and use (reg:DI 21) instead
> of (reg:SI 22) for the REG_DEAD note.
> 
>    I can see a few ways to fix this:
> 
> 1) Pass NULL for LOC to df_ref_create_structure().
> 2) Pass &regno_reg_rtx[i] for LOC to df_ref_create_structure().
> 3) Don't use DF_REF_REAL_LOC(use) if it looks like a bad idea.
> 
>    Comments? I tried option 3) and it seems to work:

   I suppose df_create_unused_note() is also affected?

   FWIW, I'm going to test this patch, but I can't any PA-RISC testing.

Index: /home/rask/cvssrc/owcc-gcc/gcc/df-problems.c
===================================================================
--- /home/rask/cvssrc/owcc-gcc/gcc/df-problems.c	(revision 129849)
+++ /home/rask/cvssrc/owcc-gcc/gcc/df-problems.c	(working copy)
@@ -2636,7 +2636,10 @@ df_create_unused_note (rtx insn, rtx old
 	|| bitmap_bit_p (artificial_uses, dregno)
 	|| df_ignore_stack_reg (dregno)))
     {
-      rtx reg = (DF_REF_LOC (def)) 
+      rtx reg = (DF_REF_LOC (def)
+		 && (GET_MODE (*DF_REF_REAL_LOC (def))
+		     == GET_MODE (DF_REF_REG (def))
+		     || !HARD_REGISTER_P (*DF_REF_REAL_LOC (def))))
                 ? *DF_REF_REAL_LOC (def): DF_REF_REG (def);
       old = df_set_note (REG_UNUSED, insn, old, reg);
 #ifdef REG_DEAD_DEBUGGING
@@ -2829,7 +2832,10 @@ df_note_bb_compute (unsigned int bb_inde
 		   && (!(DF_REF_FLAGS (use) & DF_REF_READ_WRITE))
 		   && (!df_ignore_stack_reg (uregno)))
 		{
-		  rtx reg = (DF_REF_LOC (use)) 
+		  rtx reg = (DF_REF_LOC (use)
+			     && (GET_MODE (*DF_REF_REAL_LOC (use))
+				 == GET_MODE (DF_REF_REG (use))
+				 || !HARD_REGISTER_P (*DF_REF_REAL_LOC (use))))
                             ? *DF_REF_REAL_LOC (use) : DF_REF_REG (use);
 		  old_dead_notes = df_set_note (REG_DEAD, insn, old_dead_notes, reg);
 
Index: /home/rask/cvssrc/owcc-gcc/gcc/reload1.c
===================================================================
--- /home/rask/cvssrc/owcc-gcc/gcc/reload1.c	(revision 129849)
+++ /home/rask/cvssrc/owcc-gcc/gcc/reload1.c	(working copy)
@@ -891,6 +891,19 @@ reload (rtx first, int global)
   for (i = LAST_VIRTUAL_REGISTER + 1; i < max_regno; i++)
     alter_reg (i, -1);
 
+  /* Update REG_DEAD and REG_UNUSED notes.  */
+  df_finish_pass (true);
+  df_note_add_problem ();
+  df_scan_alloc (NULL);
+  df_scan_blocks ();
+  df_analyze ();
+
+  /* There is just too much going on in the register allocators to
+     keep things up to date.  At the end we have to rescan anyway
+     because things change when the reload_completed flag is set.
+     So we just turn off scanning and we will rescan by hand.  */
+  df_set_flags (DF_NO_INSN_RESCAN);
+
   /* If we have some registers we think can be eliminated, scan all insns to
      see if there is an insn that sets one of these registers to something
      other than itself plus a constant.  If so, the register cannot be

-- 
Rask Ingemann Lambertsen
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