[llvm] [LV] Add initial support for partial alias masking (PR #177599)

[Benjamin Maxwell via llvm-commits]

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@@ -4954,6 +4955,58 @@ void VPlanTransforms::materializeVFAndVFxUF(VPlan &Plan, VPBasicBlock *VectorPH,
   VFxUF.replaceAllUsesWith(MulByUF);
 }
 
+VPValue *
+VPlanTransforms::materializeAliasMask(VPlan &Plan, VPBasicBlock *AliasCheck,
+                                      ArrayRef<PointerDiffInfo> DiffChecks) {
+  VPValue &AliasMask = Plan.getAliasMask();
+  VPBuilder Builder(AliasCheck, AliasCheck->begin());
+  Type *I1Ty = IntegerType::getInt1Ty(Plan.getContext());
+  Type *I64Ty = IntegerType::getInt64Ty(Plan.getContext());
+  Type *PtrTy = PointerType::getUnqual(Plan.getContext());
+
+  VPValue *Mask = nullptr;
+  for (PointerDiffInfo Check : DiffChecks) {
+    VPValue *Src = vputils::getOrCreateVPValueForSCEVExpr(Plan, Check.SrcStart);
+    VPValue *Sink =
+        vputils::getOrCreateVPValueForSCEVExpr(Plan, Check.SinkStart);
+
+    VPValue *SrcPtr =
+        Builder.createScalarCast(Instruction::CastOps::IntToPtr, Src, PtrTy,
+                                 DebugLoc::getCompilerGenerated());
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MacDue wrote:

The SCEV expansion inserts pointer-to-integer casts, I'm not sure if that can be avoided, but they should fold away.

https://github.com/llvm/llvm-project/pull/177599