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

[Robert Imschweiler via llvm-commits]

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@@ -495,6 +495,13 @@ class TargetTransformInfo {
 
   LLVM_ABI bool isNoopAddrSpaceCast(unsigned FromAS, unsigned ToAS) const;
 
+  LLVM_ABI std::pair<KnownBits, KnownBits>
+  computeKnownBitsAddrSpaceCast(unsigned FromAS, unsigned ToAS,
+                                const Value &PtrOp) const;
+
+  LLVM_ABI KnownBits computeKnownBitsAddrSpaceCast(
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ro-i wrote:

The addrspacecast. For example, the case where I cast larger address to smaller address, I just trunc. This might be valid for all practical cases (given integral), but it's in no way guaranteed afaiu.
Also, the anyext for smaller->larger casts is a conservative choice that could be improved with target knowledge, ig

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