[llvm] [SPIR-V] Add InferAddrSpaces pass to the backend (PR #137766)

[Steven Perron via llvm-commits]

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@@ -190,6 +191,14 @@ void SPIRVPassConfig::addIRPasses() {
   TargetPassConfig::addIRPasses();
 
   if (TM.getSubtargetImpl()->isVulkanEnv()) {
+    // The frontend has a tendency to quickly addrspacecast pointers to the
+    // default address space, and relies on addrspacecast instructions at the
+    // boundaries. Vulkan does not allow such things, and we must keep the
+    // pointer address space stable.
+    // This pass will determine real address space of a pointer, and patch
+    // instructions removing Addrspacecasts.
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s-perron wrote:

I would make the comment more succinctly and precisely.

```suggestion
    // Vulkan does not allow address space casts. This pass is run to remove address space casts that can be removed.
    // If an address space cast is not removed while targeting Vulkan, <replace with what will happen>.
```

https://github.com/llvm/llvm-project/pull/137766