[PATCH] D71370: [AArch64][SVE] Add integer arithmetic with immediate instructions.

[Eli Friedman via Phabricator via llvm-commits]

efriedma added inline comments.


================
Comment at: llvm/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp:2828
+      Imm = CurDAG->getTargetConstant(ImmVal & 0xFF, DL, MVT::i32);
+      return true;
+    case MVT::i16:
----------------
dancgr wrote:
> efriedma wrote:
> > I'd prefer to reject immediates greater than 255 here, instead of masking off the bits.
> In the immediate definition we have:
> 
> ```
> def addsub_imm8_opt_lsl_i8  : imm8_opt_lsl<8,  "uint8_t",  SVEAddSubImmOperand8,  [{
>   return AArch64_AM::isSVEAddSubImm<int8_t>(Imm);
> }]>;
> ```
> This checks if the immediate is in the accepted range for AddSub. Would you say we should also add another check here?
> 
> I pasted the code of that function below, since it is not in the changed files from this patch:
> 
> ```
> template <typename T>
> static inline bool isSVEAddSubImm(int64_t Imm) {
>   bool IsInt8t =
>       std::is_same<int8_t, typename std::make_signed<T>::type>::value;
>   return uint8_t(Imm) == Imm || (!IsInt8t && uint16_t(Imm & ~0xff) == Imm);
> }
> ```
Not sure that TableGen code is actually getting called from isel in this situation?  If it is, fine, we don't need a redundant check.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D71370/new/

https://reviews.llvm.org/D71370