[LLVMdev] How to define macros in a tablegen file?

[Sebastian Pop]

Hi,

I was wondering if there is a way to specify macros to help shorten
rewriting patterns like these:

def : Pat <(v4i8 (mul (v4i8 IntRegs:$a), (v4i8 IntRegs:$b))),
  (v4i8
   (VTRUNEHB
    (v4i16
     (VTRUNEWH
      (v2i32
       (VMPYH
        (v2i16
         (EXTRACT_SUBREG (v4i16 (VSXTBH (v4i8 IntRegs:$a))), subreg_hireg)),
        (v2i16
         (EXTRACT_SUBREG (v4i16 (VSXTBH (v4i8 IntRegs:$b))), subreg_hireg)))),
      (v2i32
       (VMPYH
        (v2i16
         (EXTRACT_SUBREG (v4i16 (VSXTBH (v4i8 IntRegs:$a))), subreg_loreg)),
        (v2i16
         (EXTRACT_SUBREG (v4i16 (VSXTBH (v4i8 IntRegs:$b))), subreg_loreg)))))))
  )>;


Basically if we have a way to name a dag foo to be this:
(EXTRACT_SUBREG (v4i16 (VSXTBH $X)), $Y)

and bar to stand for this:
(v2i32 (VMPYH (v2i16 (foo $X, $Z)), (v2i16 (foo $Y, $Z))))

then, I could write the same pattern in a shorter format:
def : Pat <(v4i8 (mul (v4i8 IntRegs:$a), (v4i8 IntRegs:$b))),
  (v4i8
   (VTRUNEHB
    (v4i16
     (VTRUNEWH (bar IntRegs:$a, IntRegs:$b, subreg_hireg),
               (bar IntRegs:$a, IntRegs:$b, subreg_loreg)))))
  >;

Thanks,
Sebastian
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