re PR rtl-optimization/84123 (internal compiler error: in gen_rtx_SUBREG, at…

re PR rtl-optimization/84123 (internal compiler error: in gen_rtx_SUBREG, at emit-rtl.c:908, alpha linux.)

	PR rtl-optimization/84123
	* combine.c (change_zero_ext): Check if hard register satisfies
	can_change_dest_mode before calling gen_lowpart_SUBREG.

From-SVN: r257270

gcc/ChangeLog

+2018-01-31  Uros Bizjak  <ubizjak@gmail.com>
+
+	PR rtl-optimization/84123
+	* combine.c (change_zero_ext): Check if hard register satisfies
+	can_change_dest_mode before calling gen_lowpart_SUBREG.
+
 2018-01-31  Vladimir Makarov  <vmakarov@redhat.com>
 
 	PR target/82444

gcc/combine.c

@@ -11480,8 +11480,15 @@ change_zero_ext (rtx pat)
 				  gen_int_shift_amount (inner_mode, start));
 	  else
 	    x = XEXP (x, 0);
+
 	  if (mode != inner_mode)
-	    x = gen_lowpart_SUBREG (mode, x);
+	    {
+	      if (HARD_REGISTER_P (x)
+		  && !can_change_dest_mode (x, 0, mode))
+		continue;
+
+	      x = gen_lowpart_SUBREG (mode, x);
+	    }
 	}
       else if (GET_CODE (x) == ZERO_EXTEND
 	       && GET_CODE (XEXP (x, 0)) == SUBREG
@@ -11493,7 +11500,13 @@ change_zero_ext (rtx pat)
 	  size = GET_MODE_PRECISION (inner_mode);
 	  x = SUBREG_REG (XEXP (x, 0));
 	  if (GET_MODE (x) != mode)
-	    x = gen_lowpart_SUBREG (mode, x);
+	    {
+	      if (HARD_REGISTER_P (x)
+		  && !can_change_dest_mode (x, 0, mode))
+		continue;
+
+	      x = gen_lowpart_SUBREG (mode, x);
+	    }
 	}
       else if (GET_CODE (x) == ZERO_EXTEND
 	       && REG_P (XEXP (x, 0))