GNU Compiler Collection (GCC) Internals: Examples

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#### 16.23.1.3 Mode Iterator Examples

Here is an example from the MIPS port. It defines the following modes and attributes (among others):

    (define_mode_iterator GPR [SI (DI "TARGET_64BIT")])
    (define_mode_attr d [(SI "") (DI "d")])

and uses the following template to define both `subsi3` and `subdi3`:

    (define_insn "sub<mode>3"
      [(set (match_operand:GPR 0 "register_operand" "=d")
            (minus:GPR (match_operand:GPR 1 "register_operand" "d")
                       (match_operand:GPR 2 "register_operand" "d")))]
      ""
      "<d>subu\t%0,%1,%2"
      [(set_attr "type" "arith")
       (set_attr "mode" "<MODE>")])

This is exactly equivalent to:

    (define_insn "subsi3"
      [(set (match_operand:SI 0 "register_operand" "=d")
            (minus:SI (match_operand:SI 1 "register_operand" "d")
                      (match_operand:SI 2 "register_operand" "d")))]
      ""
      "subu\t%0,%1,%2"
      [(set_attr "type" "arith")
       (set_attr "mode" "SI")])

    (define_insn "subdi3"
      [(set (match_operand:DI 0 "register_operand" "=d")
            (minus:DI (match_operand:DI 1 "register_operand" "d")
                      (match_operand:DI 2 "register_operand" "d")))]
      ""
      "dsubu\t%0,%1,%2"
      [(set_attr "type" "arith")
       (set_attr "mode" "DI")])