Subzero: Translate the unreachable bitcode directly to ud2.

runtime/szrt.c

 //===- subzero/runtime/szrt.c - Subzero runtime source ----------*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the runtime helper routines that are needed by
 // Subzero.  This needs to be compiled by some non-Subzero compiler.
 //
 //===----------------------------------------------------------------------===//
 
 #include <stdint.h>
 #include <stdlib.h>
 
-void ice_unreachable(void) { abort(); }
-
 uint32_t cvtftoui32(float value) { return (uint32_t)value; }
 
 uint32_t cvtdtoui32(double value) { return (uint32_t)value; }
 
 int64_t cvtftosi64(float value) { return (int64_t)value; }
 
 int64_t cvtdtosi64(double value) { return (int64_t)value; }
 
 uint64_t cvtftoui64(float value) { return (uint64_t)value; }
 
@@ skipping 10 matching lines @@
 double cvtsi64tod(int64_t value) { return (double)value; }
 
 double cvtui64tod(uint64_t value) { return (double)value; }
 
 /* TODO(stichnot):
    Sz_bitcast_v8i1_to_i8
    Sz_bitcast_v16i1_to_i16
    Sz_bitcast_i8_to_v8i1
    Sz_bitcast_i16_to_v16i1
 */