var-tracking.c (use_narrower_mode_test, [...]): New functions.

	* var-tracking.c (use_narrower_mode_test, use_narrower_mode): New
	functions.
	(adjust_mems): Replace narrowing SUBREG of expression containing
	just PLUS, MINUS, MULT and ASHIFT of registers and constants
	with operations in the narrower mode.

From-SVN: r157835

gcc/ChangeLog

 2010-03-30  Jakub Jelinek  <jakub@redhat.com>
 
+	* var-tracking.c (use_narrower_mode_test, use_narrower_mode): New
+	functions.
+	(adjust_mems): Replace narrowing SUBREG of expression containing
+	just PLUS, MINUS, MULT and ASHIFT of registers and constants
+	with operations in the narrower mode.
+
 	PR debug/43593
 	* var-tracking.c (dataflow_set_clear_at_call): Invalidate
 	just regs_invalidated_by_call instead all call_used_reg_set

gcc/var-tracking.c

@@ -729,6 +729,65 @@ struct adjust_mem_data
   rtx side_effects;
 };
 
+/* Helper for adjust_mems.  Return 1 if *loc is unsuitable for
+   transformation of wider mode arithmetics to narrower mode,
+   -1 if it is suitable and subexpressions shouldn't be
+   traversed and 0 if it is suitable and subexpressions should
+   be traversed.  Called through for_each_rtx.  */
+
+static int
+use_narrower_mode_test (rtx *loc, void *data)
+{
+  rtx subreg = (rtx) data;
+
+  if (CONSTANT_P (*loc))
+    return -1;
+  switch (GET_CODE (*loc))
+    {
+    case REG:
+      if (cselib_lookup (*loc, GET_MODE (SUBREG_REG (subreg)), 0))
+	return 1;
+      return -1;
+    case PLUS:
+    case MINUS:
+    case MULT:
+      return 0;
+    case ASHIFT:
+      if (for_each_rtx (&XEXP (*loc, 0), use_narrower_mode_test, data))
+	return 1;
+      else
+	return -1;
+    default:
+      return 1;
+    }
+}
+
+/* Transform X into narrower mode MODE from wider mode WMODE.  */
+
+static rtx
+use_narrower_mode (rtx x, enum machine_mode mode, enum machine_mode wmode)
+{
+  rtx op0, op1;
+  if (CONSTANT_P (x))
+    return lowpart_subreg (mode, x, wmode);
+  switch (GET_CODE (x))
+    {
+    case REG:
+      return lowpart_subreg (mode, x, wmode);
+    case PLUS:
+    case MINUS:
+    case MULT:
+      op0 = use_narrower_mode (XEXP (x, 0), mode, wmode);
+      op1 = use_narrower_mode (XEXP (x, 1), mode, wmode);
+      return simplify_gen_binary (GET_CODE (x), mode, op0, op1);
+    case ASHIFT:
+      op0 = use_narrower_mode (XEXP (x, 0), mode, wmode);
+      return simplify_gen_binary (ASHIFT, mode, op0, XEXP (x, 1));
+    default:
+      gcc_unreachable ();
+    }
+}
+
 /* Helper function for adjusting used MEMs.  */
 
 static rtx
@@ -822,18 +881,36 @@ adjust_mems (rtx loc, const_rtx old_rtx, void *data)
       amd->store = store_save;
       mem = simplify_replace_fn_rtx (addr, old_rtx, adjust_mems, data);
       if (mem == SUBREG_REG (loc))
-	return loc;
+	{
+	  tem = loc;
+	  goto finish_subreg;
+	}
       tem = simplify_gen_subreg (GET_MODE (loc), mem,
 				 GET_MODE (SUBREG_REG (loc)),
 				 SUBREG_BYTE (loc));
       if (tem)
-	return tem;
+	goto finish_subreg;
       tem = simplify_gen_subreg (GET_MODE (loc), addr,
 				 GET_MODE (SUBREG_REG (loc)),
 				 SUBREG_BYTE (loc));
-      if (tem)
-	return tem;
-      return gen_rtx_raw_SUBREG (GET_MODE (loc), addr, SUBREG_BYTE (loc));
+      if (tem == NULL_RTX)
+	tem = gen_rtx_raw_SUBREG (GET_MODE (loc), addr, SUBREG_BYTE (loc));
+    finish_subreg:
+      if (MAY_HAVE_DEBUG_INSNS
+	  && GET_CODE (tem) == SUBREG
+	  && (GET_CODE (SUBREG_REG (tem)) == PLUS
+	      || GET_CODE (SUBREG_REG (tem)) == MINUS
+	      || GET_CODE (SUBREG_REG (tem)) == MULT
+	      || GET_CODE (SUBREG_REG (tem)) == ASHIFT)
+	  && GET_MODE_CLASS (GET_MODE (tem)) == MODE_INT
+	  && GET_MODE_CLASS (GET_MODE (SUBREG_REG (tem))) == MODE_INT
+	  && GET_MODE_SIZE (GET_MODE (tem))
+	     < GET_MODE_SIZE (GET_MODE (SUBREG_REG (tem)))
+	  && subreg_lowpart_p (tem)
+	  && !for_each_rtx (&SUBREG_REG (tem), use_narrower_mode_test, tem))
+	return use_narrower_mode (SUBREG_REG (tem), GET_MODE (tem),
+				  GET_MODE (SUBREG_REG (tem)));
+      return tem;
     default:
       break;
     }