[llvm] [InferAddressSpaces] Handle unconverted ptrmask (PR #140802)

[Robert Imschweiler via llvm-commits]

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@@ -151,6 +152,54 @@ class TargetTransformInfoImplBase {
   }
 
   virtual bool isNoopAddrSpaceCast(unsigned, unsigned) const { return false; }
+
+  // Given an address space cast of the given pointer value, calculate the known
+  // bits of the source pointer in the source addrspace and the destination
+  // pointer in the destination addrspace.
+  virtual std::pair<KnownBits, KnownBits>
+  computeKnownBitsAddrSpaceCast(unsigned FromAS, unsigned ToAS,
+                                const Value &PtrOp) const {
+    if (DL.isNonIntegralAddressSpace(FromAS))
+      return std::pair(KnownBits(DL.getPointerSizeInBits(FromAS)),
+                       KnownBits(DL.getPointerSizeInBits(ToAS)));
+
+    KnownBits FromPtrBits;
+    if (const AddrSpaceCastInst *CastI = dyn_cast<AddrSpaceCastInst>(&PtrOp)) {
+      std::pair<KnownBits, KnownBits> KB = computeKnownBitsAddrSpaceCast(
+          CastI->getSrcAddressSpace(), CastI->getDestAddressSpace(),
+          *CastI->getPointerOperand());
+      FromPtrBits = KB.second;
+    } else if (isa<ConstantPointerNull>(PtrOp) && FromAS == 0) {
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ro-i wrote:

`isNullValue` is not directly callable on `PtrOp`, but I think I implemented what you meant

https://github.com/llvm/llvm-project/pull/140802