[clang] [llvm] [llvm][opt][Transforms][SPIR-V] Enable `InferAddressSpaces` for SPIR-V (PR #110897)

[Matt Arsenault via cfe-commits]

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@@ -91,6 +97,100 @@ SPIRVTargetMachine::SPIRVTargetMachine(const Target &T, const Triple &TT,
   setRequiresStructuredCFG(false);
 }
 
+enum AddressSpace {
+  Function = storageClassToAddressSpace(SPIRV::StorageClass::Function),
+  CrossWorkgroup =
+      storageClassToAddressSpace(SPIRV::StorageClass::CrossWorkgroup),
+  UniformConstant =
+      storageClassToAddressSpace(SPIRV::StorageClass::UniformConstant),
+  Workgroup = storageClassToAddressSpace(SPIRV::StorageClass::Workgroup),
+  Generic = storageClassToAddressSpace(SPIRV::StorageClass::Generic)
+};
+
+unsigned SPIRVTargetMachine::getAssumedAddrSpace(const Value *V) const {
+  // TODO: we only enable this for AMDGCN flavoured SPIR-V, where we know it to
+  //       be correct; this might be relaxed in the future.
+  if (getTargetTriple().getVendor() != Triple::VendorType::AMD)
+    return UINT32_MAX;
+
+  const auto *LD = dyn_cast<LoadInst>(V);
+  if (!LD)
+    return UINT32_MAX;
+
+  // It must be a load from a pointer to Generic.
+  assert(V->getType()->isPointerTy() &&
+         V->getType()->getPointerAddressSpace() == AddressSpace::Generic);
+
+  const auto *Ptr = LD->getPointerOperand();
+  if (Ptr->getType()->getPointerAddressSpace() != AddressSpace::UniformConstant)
+    return UINT32_MAX;
+  // For a loaded from a pointer to UniformConstant, we can infer CrossWorkgroup
+  // storage, as this could only have been legally initialised with a
+  // CrossWorkgroup (aka device) constant pointer.
+  return AddressSpace::CrossWorkgroup;
+}
+
+std::pair<const Value *, unsigned>
+SPIRVTargetMachine::getPredicatedAddrSpace(const Value *V) const {
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arsenm wrote:

Drop this part from the patch, it's not tested and is questionable enough to do separately 

https://github.com/llvm/llvm-project/pull/110897