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A few simple DImode improvements

Message ID 4C3DD524.7010206@codesourcery.com
State New
Headers show

Commit Message

Bernd Schmidt July 14, 2010, 3:17 p.m. UTC 
On 07/14/2010 05:12 PM, Ian Lance Taylor wrote:
> Bernd Schmidt <bernds@codesourcery.com> writes:
> 
>> 	* lower-subreg.c (subreg_context): New static bitmap.
>> 	(decompose_multiword_subregs): Allocate and free it.
>> 	(find_decomposable_subregs): Set a bit in it for a register that
>> 	occurs in a subreg that changes mode but not size.
>> 	(can_decompose_p): Test it instead of non_decomposable_context.
> 
> This looks fine to me.  A longer comment for subreg_context might be
> appropriate, to explain why we think it might be necessary.

Thanks.  Here's what I committed.


Bernd
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Patch

Index: ChangeLog
===================================================================
--- ChangeLog	(revision 162180)
+++ ChangeLog	(working copy)
@@ -1,3 +1,11 @@ 
+2010-07-14  Bernd Schmidt  <bernds@codesourcery.com>
+
+	* lower-subreg.c (subreg_context): New static bitmap.
+	(decompose_multiword_subregs): Allocate and free it.
+	(find_decomposable_subregs): Set a bit in it for a register that
+	occurs in a subreg that changes mode but not size.
+	(can_decompose_p): Test it instead of non_decomposable_context.
+
 2010-07-14  Richard Guenther  <rguenther@suse.de>
 
 	PR tree-optimization/44824
Index: lower-subreg.c
===================================================================
--- lower-subreg.c	(revision 162146)
+++ lower-subreg.c	(working copy)
@@ -63,6 +63,12 @@  static bitmap decomposable_context;
    which it can not be decomposed.  */
 static bitmap non_decomposable_context;
 
+/* Bit N in this bitmap is set if regno N is used in a subreg
+   which changes the mode but not the size.  This typically happens
+   when the register accessed as a floating-point value; we want to
+   avoid generating accesses to its subwords in integer modes.  */
+static bitmap subreg_context;
+
 /* Bit N in the bitmap in element M of this array is set if there is a
    copy from reg M to reg N.  */
 static VEC(bitmap,heap) *reg_copy_graph;
@@ -289,6 +295,7 @@  find_decomposable_subregs (rtx *px, void
 	  && !MODES_TIEABLE_P (GET_MODE (x), GET_MODE (inner)))
 	{
 	  bitmap_set_bit (non_decomposable_context, regno);
+	  bitmap_set_bit (subreg_context, regno);
 	  return -1;
 	}
     }
@@ -616,7 +623,7 @@  can_decompose_p (rtx x)
 	return (validate_subreg (word_mode, GET_MODE (x), x, UNITS_PER_WORD)
 		&& HARD_REGNO_MODE_OK (regno, word_mode));
       else
-	return !bitmap_bit_p (non_decomposable_context, regno);
+	return !bitmap_bit_p (subreg_context, regno);
     }
 
   return true;
@@ -1091,6 +1098,7 @@  decompose_multiword_subregs (void)
 
   decomposable_context = BITMAP_ALLOC (NULL);
   non_decomposable_context = BITMAP_ALLOC (NULL);
+  subreg_context = BITMAP_ALLOC (NULL);
 
   reg_copy_graph = VEC_alloc (bitmap, heap, max);
   VEC_safe_grow (bitmap, heap, reg_copy_graph, max);
@@ -1309,6 +1317,7 @@  decompose_multiword_subregs (void)
 
   BITMAP_FREE (decomposable_context);
   BITMAP_FREE (non_decomposable_context);
+  BITMAP_FREE (subreg_context);
 }
 
 /* Gate function for lower subreg pass.  */