[PATCH] D133700: [PowerPC] Exploit xxperm, check for dead vectors and substitute vperm with xxperm

[Maryam Moghadas via Phabricator via llvm-commits]

maryammo added inline comments.


================
Comment at: llvm/lib/Target/PowerPC/PPCInstrVSX.td:91
+  SDTCisVT<0, v2f64>, SDTCisVT<1, v2f64>,
+  SDTCisVT<2, v2f64>]>;
 //--------------------------- Custom PPC nodes -------------------------------//
----------------
stefanp wrote:
> maryammo wrote:
> > stefanp wrote:
> > > Is it possible to add a type constraint for the last operand here?  
> > > ```
> > > SDTCisVT<3, v4i32>
> > > ```
> > > Or is that going to cause issues elsewhere?
> > The last one is  SDTCisVT<2, v2f64> that has a different type constraint, are you suggesting to change it?
> No, I think that constraint is fine.
> What I'm saying is that this `SDTypeProfile<1, 3,` has 1 output and 3 inputs. 
> Currently, the output and the first 2 inputs have a constraint but the last input doesn't have a constraint.
> 
> So, what I'm thinking of is:
> ```
> --- a/llvm/lib/Target/PowerPC/PPCInstrVSX.td
> +++ b/llvm/lib/Target/PowerPC/PPCInstrVSX.td
> @@ -88,7 +88,7 @@ def SDT_PPCst_vec_be : SDTypeProfile<0, 2, [
>  
>  def SDT_PPCxxperm : SDTypeProfile<1, 3, [
>    SDTCisVT<0, v2f64>, SDTCisVT<1, v2f64>,
> -  SDTCisVT<2, v2f64>]>;
> +  SDTCisVT<2, v2f64>, SDTCisVT<3, v4i32>]>;
>  //--------------------------- Custom PPC nodes -------------------------------//
>  def PPClxvd2x  : SDNode<"PPCISD::LXVD2X", SDT_PPClxvd2x,
>                          [SDNPHasChain, SDNPMayLoad, SDNPMemOperand]>;
> @@ -4151,8 +4151,8 @@ def : Pat<(v8i16 (PPCldsplat ForceXForm:$A)),
>            (v8i16 (VSPLTHs 3, (LXSIHZX ForceXForm:$A)))>;
>  def : Pat<(v16i8 (PPCldsplat ForceXForm:$A)),
>            (v16i8 (VSPLTBs 7, (LXSIBZX ForceXForm:$A)))>;
> -def : Pat<(v2f64 (PPCxxperm v2f64:$XT, v2f64:$XB, (v16i8 (bitconvert v4i32:$C)))),
> -          (XXPERM v2f64:$XT, v2f64:$XB, v4i32:$C)>;
>  def : Pat<(v2f64 (PPCxxperm v2f64:$XT, v2f64:$XB, v4i32:$C)),
>            (XXPERM v2f64:$XT, v2f64:$XB, v4i32:$C)>;
>  } // HasVSX, HasP9Vector
> ```
Such a change causes build failure which seems to be related to 
def : Pat<(v2f64 (PPCxxperm v2f64:$XT, v2f64:$XB, (v16i8 (bitconvert v4i32:$C)))),
                             (XXPERM v2f64:$XT, v2f64:$XB, v4i32:$C)>;



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  https://reviews.llvm.org/D133700/new/

https://reviews.llvm.org/D133700