[PATCH] D71831: [PowerPC] Exploit the rldicl + rldicl when and with mask

[qshanz via Phabricator via llvm-commits]

steven.zhang marked an inline comment as done.
steven.zhang added inline comments.


================
Comment at: llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp:4478
+  }
+
+  // We can do special handling for pattern like this.
----------------
shchenz wrote:
> For special case, form a new Imm, like:
> ```
>   APInt Res(64, Imm64);                                                                                                                                
>   ClearBits = Res.countLeadingZeros();                                                                                                                 
>   if (ClearBits != 0) {                                                                                                                                
>     // change pattern |0001111100000011111111|                                                                                                         
>     //                       to |1111111100000011111111|                                                                                                         
>     APInt Mask = APInt::getBitsSet(64, 64 - ClearBits, 64);                                                                                            
>     Res = Res | Mask;                                                                                                                                  
>     Imm64 = Res.getZExtValue();                                                                                                                        
>   }                                                                                                                                                                                                                                                                                    
> ```
> And pass new Imm64 and ClearBits to normal case, I think logic here maybe a little simple?
Good suggestion.


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https://reviews.llvm.org/D71831