[58/67] Use scalar_int_mode in a try_combine optimisation

[Richard Sandiford <richard dot sandiford at arm dot com>]

This patch uses scalar_int_modes for:

  /* If I2 is setting a pseudo to a constant and I3 is setting some
     sub-part of it to another constant, merge them by making a new
     constant.  */

This was already implicit, but the danger with just checking
CONST_SCALAR_INT_P is that it can include CC values too.

gcc/
2016-11-24  Richard Sandiford  <richard.sandiford@arm.com>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

	* combine.c (try_combine): Use is_a <scalar_int_mode> when
	trying to combine a full-register integer set with a subreg
	integer set.

diff --git a/gcc/combine.c b/gcc/combine.c
index 6e32b37..dd7f1fa 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -2631,6 +2631,7 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1, rtx_insn *i0,
   rtx other_pat = 0;
   rtx new_other_notes;
   int i;
+  scalar_int_mode dest_mode, temp_mode;
 
   /* Immediately return if any of I0,I1,I2 are the same insn (I3 can
      never be).  */
@@ -2831,33 +2832,40 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1, rtx_insn *i0,
      constant.  */
   if (i1 == 0
       && (temp_expr = single_set (i2)) != 0
+      && is_a <scalar_int_mode> (GET_MODE (SET_DEST (temp_expr)), &temp_mode)
       && CONST_SCALAR_INT_P (SET_SRC (temp_expr))
       && GET_CODE (PATTERN (i3)) == SET
       && CONST_SCALAR_INT_P (SET_SRC (PATTERN (i3)))
       && reg_subword_p (SET_DEST (PATTERN (i3)), SET_DEST (temp_expr)))
     {
       rtx dest = SET_DEST (PATTERN (i3));
+      rtx temp_dest = SET_DEST (temp_expr);
       int offset = -1;
       int width = 0;
-      
+
       if (GET_CODE (dest) == ZERO_EXTRACT)
 	{
 	  if (CONST_INT_P (XEXP (dest, 1))
-	      && CONST_INT_P (XEXP (dest, 2)))
+	      && CONST_INT_P (XEXP (dest, 2))
+	      && is_a <scalar_int_mode> (GET_MODE (XEXP (dest, 0)),
+					 &dest_mode))
 	    {
 	      width = INTVAL (XEXP (dest, 1));
 	      offset = INTVAL (XEXP (dest, 2));
 	      dest = XEXP (dest, 0);
 	      if (BITS_BIG_ENDIAN)
-		offset = GET_MODE_PRECISION (GET_MODE (dest)) - width - offset;
+		offset = GET_MODE_PRECISION (dest_mode) - width - offset;
 	    }
 	}
       else
 	{
 	  if (GET_CODE (dest) == STRICT_LOW_PART)
 	    dest = XEXP (dest, 0);
-	  width = GET_MODE_PRECISION (GET_MODE (dest));
-	  offset = 0;
+	  if (is_a <scalar_int_mode> (GET_MODE (dest), &dest_mode))
+	    {
+	      width = GET_MODE_PRECISION (dest_mode);
+	      offset = 0;
+	    }
 	}
 
       if (offset >= 0)
@@ -2866,9 +2874,9 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1, rtx_insn *i0,
 	  if (subreg_lowpart_p (dest))
 	    ;
 	  /* Handle the case where inner is twice the size of outer.  */
-	  else if (GET_MODE_PRECISION (GET_MODE (SET_DEST (temp_expr)))
-		   == 2 * GET_MODE_PRECISION (GET_MODE (dest)))
-	    offset += GET_MODE_PRECISION (GET_MODE (dest));
+	  else if (GET_MODE_PRECISION (temp_mode)
+		   == 2 * GET_MODE_PRECISION (dest_mode))
+	    offset += GET_MODE_PRECISION (dest_mode);
 	  /* Otherwise give up for now.  */
 	  else
 	    offset = -1;
@@ -2879,23 +2887,22 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1, rtx_insn *i0,
 	  rtx inner = SET_SRC (PATTERN (i3));
 	  rtx outer = SET_SRC (temp_expr);
 
-	  wide_int o
-	    = wi::insert (rtx_mode_t (outer, GET_MODE (SET_DEST (temp_expr))),
-			  rtx_mode_t (inner, GET_MODE (dest)),
-			  offset, width);
+	  wide_int o = wi::insert (rtx_mode_t (outer, temp_mode),
+				   rtx_mode_t (inner, dest_mode),
+				   offset, width);
 
 	  combine_merges++;
 	  subst_insn = i3;
 	  subst_low_luid = DF_INSN_LUID (i2);
 	  added_sets_2 = added_sets_1 = added_sets_0 = 0;
-	  i2dest = SET_DEST (temp_expr);
+	  i2dest = temp_dest;
 	  i2dest_killed = dead_or_set_p (i2, i2dest);
 
 	  /* Replace the source in I2 with the new constant and make the
 	     resulting insn the new pattern for I3.  Then skip to where we
 	     validate the pattern.  Everything was set up above.  */
 	  SUBST (SET_SRC (temp_expr),
-		 immed_wide_int_const (o, GET_MODE (SET_DEST (temp_expr))));
+		 immed_wide_int_const (o, temp_mode));
 
 	  newpat = PATTERN (i2);