[PATCH] D74856: [AArch64][SVE] Add backend support for splats of immediates

[Eli Friedman via Phabricator via llvm-commits]

efriedma added inline comments.


================
Comment at: llvm/lib/Target/AArch64/AArch64SVEInstrInfo.td:13
 
+def SVE8BitLslImm : ComplexPattern<i32, 2, "SelectSVE8BitLslImm", [imm]>;
+
----------------
cameron.mcinally wrote:
> cameron.mcinally wrote:
> > efriedma wrote:
> > > cameron.mcinally wrote:
> > > > efriedma wrote:
> > > > > Is there some reason you can't use the existing cpy_imm8_opt_lsl_i8?
> > > > I'm not sure I understand this one. What should I replace with cpy_imm8_opt_lsl_i8?
> > > > 
> > > > SVE8BitLslImm is looking for two i8 immediates (i8 value and i8 shift amount).
> > > > 
> > > > cpy_imm8_opt_lsl_i8 is just checking for one i8 immediate, IINM.
> > > "class imm8_opt_lsl" has some code which looks like it supposed to be used for matching.  Granted, it's using ImmLeaf, so maybe it's just broken.
> > Oh, yeah, I see what you mean now. I'll dig into that...
> Looking closer, this seems to be in line with the other ComplexPattern uses (e.g. SVEAddSubImm8Pat).
> 
> The SVE8BitLslImm ComplexPattern is used to match the two i8 operands, $imm and $shift. If I tried to use cpy_imm8_opt_lsl_i64 in its place, I don't see a way to get the individual operands by name. E.g. something like:
> 
> ```
>   def : Pat<(nxv2i64 (AArch64dup (i64 (cpy_imm8_opt_lsl_i64 i64:$imm)))),
>             (DUP_ZI_D $???, $???)>;
> ```
If you write something like `SVE8BitLslImm:$a`, it actually counts as two operands, I think, because that's what the ComplexPattern specifies?  Not completely sure.

Orthogonal to that, if we aren't going to use the predicates in cpy_imm8_opt_lsl_i64 etc., we should get rid of them.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D74856/new/

https://reviews.llvm.org/D74856