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

[ChenZheng via Phabricator via llvm-commits]

shchenz added inline comments.


================
Comment at: llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp:4478
+  }
+
+  // We can do special handling for pattern like this.
----------------
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?


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D71831/new/

https://reviews.llvm.org/D71831