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

[Matt Arsenault via llvm-commits]

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@@ -153,23 +153,63 @@ class TargetTransformInfoImplBase {
 
   virtual bool isNoopAddrSpaceCast(unsigned, unsigned) const { return false; }
 
-  // Assuming that the cast between the two given addrspaces is not a noop,
-  // calculate the known bits of the resulting ptr in the destination addrspace.
-  // The default implementation returns 0 known bits in case either one of the
-  // addrspaces is not integral or the bit size of the source addrspace is
-  // smaller than the bit size of the destination addrspace.
-  virtual KnownBits computeKnownBitsAddrSpaceCast(unsigned FromAS,
-                                                  unsigned ToAS) const {
-    if (DL.isNonIntegralAddressSpace(FromAS) ||
-        DL.isNonIntegralAddressSpace(ToAS))
-      return 0;
-    unsigned FromASBitSize = DL.getPointerSizeInBits(FromAS);
+  // 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.
+  // The default implementation returns an empty optional in case one of the
+  // addrspaces is not integral.
+  virtual std::optional<std::pair<KnownBits, KnownBits>>
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arsenm wrote:

This doesn't need to return an optional; the default can simply return a completely unknown value 

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