2018-04-10  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/85300
	* combine.c (subst): Handle subst of CONST_SCALAR_INT_P new_rtx also
	into FLOAT and UNSIGNED_FLOAT like ZERO_EXTEND, return a CLOBBER if
	simplify_unary_operation fails.

	* gcc.dg/pr85300.c: New test.

--- gcc/combine.c.jj	2018-04-09 20:15:43.704632013 +0200
+++ gcc/combine.c	2018-04-10 09:06:25.826606396 +0200
@@ -5575,11 +5575,15 @@ subst (rtx x, rtx from, rtx to, int in_d
 		    x = gen_rtx_CLOBBER (mode, const0_rtx);
 		}
 	      else if (CONST_SCALAR_INT_P (new_rtx)
-		       && GET_CODE (x) == ZERO_EXTEND)
+		       && (GET_CODE (x) == ZERO_EXTEND
+			   || GET_CODE (x) == FLOAT
+			   || GET_CODE (x) == UNSIGNED_FLOAT))
 		{
-		  x = simplify_unary_operation (ZERO_EXTEND, GET_MODE (x),
-						new_rtx, GET_MODE (XEXP (x, 0)));
-		  gcc_assert (x);
+		  x = simplify_unary_operation (GET_CODE (x), GET_MODE (x),
+						new_rtx,
+						GET_MODE (XEXP (x, 0)));
+		  if (!x)
+		    return gen_rtx_CLOBBER (VOIDmode, const0_rtx);
 		}
 	      else
 		SUBST (XEXP (x, i), new_rtx);
--- gcc/testsuite/gcc.dg/pr85300.c.jj	2018-04-10 08:53:04.594782804 +0200
+++ gcc/testsuite/gcc.dg/pr85300.c	2018-04-10 08:53:04.594782804 +0200
@@ -0,0 +1,16 @@
+/* PR rtl-optimization/85300 */
+/* { dg-do compile } */
+/* { dg-options "-O1 -g -funroll-all-loops -fno-tree-ter -fno-web" } */
+
+void
+foo (double x, unsigned char y)
+{
+  while ((int) x < 1)
+    {
+      float a;
+
+      a = y | 0x100;
+      y = 0;
+      x = a;
+    }
+}