Add Om1 lowering with no optimizations

crosstest/test_arith.def

+#ifndef TEST_ARITH_DEF
+#define TEST_ARITH_DEF
+
+#define XSTR(s) STR(s)
+#define STR(s) #s
+
+#define UINTOP_TABLE \
+  /* inst, operator, div */ \
+  X(Add,   +,        0 )    \
+  X(Sub,   -,        0 )    \
+  X(Mul,   *,        0 )    \
+  X(Udiv,  /,        1 )    \
+  X(Urem,  %,        1 )    \
+  X(Shl,   <<,       0)     \
+  X(Lshr,  >>,       0)     \
+  X(And,   &,        0 )    \
+  X(Or,    |,        0 )    \
+  X(Xor,   ^,        0 )    \
+//#define X(inst, op, isdiv)
+
+#define SINTOP_TABLE \
+  /* inst, operator, div */ \
+  X(Sdiv,  /,        1)     \
+  X(Srem,  %,        1)     \
+  X(Ashr,  >>,       0)     \
+//#define X(inst, op, isdiv)
+
+#define COMMA ,
+#define FPOP_TABLE \
+  /* inst, infix_op, func */ \
+  X(Fadd,  +,              ) \
+  X(Fsub,  -,              ) \
+  X(Fmul,  *,              ) \
+  X(Fdiv,  /,              ) \
+  X(Frem,  COMMA,    myFrem) \
+//#define X(inst, op, func)
+
+// Note: The above definition of COMMA, plus the "func" argument to
+// the X macro, are because C++ does not allow the % operator on
+// floating-point primitive types.  To work around this, the expansion
+// is "func(a infix_op b)", which becomes "myFrem(a , b)" for the Frem
+// instruction and "(a + b)" for the Fadd instruction.  The two
+// versions of myFrem() are defined in a separate bitcode file.
+
+#endif // TEST_ARITH_DEF