[llvm] Update the base and index value for masked gather (PR #130920)

[Rohit Aggarwal via llvm-commits]

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@@ -61619,3 +61624,99 @@ Align X86TargetLowering::getPrefLoopAlignment(MachineLoop *ML) const {
     return Align(1ULL << ExperimentalPrefInnermostLoopAlignment);
   return TargetLowering::getPrefLoopAlignment();
 }
+
+// Target override this function to decided whether it want to update the base
+// and index value of a non-uniform gep
+bool X86TargetLowering::updateBaseAndIndex(const Value *Ptr, SDValue &Base,
+                                           SDValue &Index, const SDLoc &DL,
+                                           const SDValue &Gep,
+                                           SelectionDAG &DAG,
+                                           const BasicBlock *CurBB) const {
+  if (!EnableBaseIndexUpdate)
+    return false;
+
+  const GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Ptr);
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rohitaggarwal007 wrote:

To check whether ptr is derived from GEP. If not, we return false and transformation does not happen. 
If the check does not fit here, i can move it to callsite

https://github.com/llvm/llvm-project/pull/130920