re PR rtl-optimization/56484 (ICE in assign_by_spills, at lra-assigns.c:1268)

	PR rtl-optimization/56484
	* ifcvt.c (noce_process_if_block): If else_bb is NULL, avoid extending
	lifetimes of hard registers on small register class machines.

From-SVN: r196478

gcc/ifcvt.c

@@ -2491,6 +2491,12 @@ noce_process_if_block (struct noce_if_info *if_info)
 	  || ! noce_operand_ok (SET_SRC (set_b))
 	  || reg_overlap_mentioned_p (x, SET_SRC (set_b))
 	  || modified_between_p (SET_SRC (set_b), insn_b, jump)
+	  /* Avoid extending the lifetime of hard registers on small
+	     register class machines.  */
+	  || (REG_P (SET_SRC (set_b))
+	      && HARD_REGISTER_P (SET_SRC (set_b))
+	      && targetm.small_register_classes_for_mode_p
+		   (GET_MODE (SET_SRC (set_b))))
 	  /* Likewise with X.  In particular this can happen when
 	     noce_get_condition looks farther back in the instruction
 	     stream than one might expect.  */

gcc/testsuite/gcc.c-torture/compile/pr56484.c

+/* PR rtl-optimization/56484 */
+
+unsigned char b[4096];
+int bar (void);
+
+int
+foo (void)
+{
+  int a = 0;
+  while (bar ())
+    {
+      int c = bar ();
+      a = a < 0 ? a : c;
+      __builtin_memset (b, 0, sizeof b);
+    }
+  return a;
+}