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

[Victor Lomuller 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.
+    addPass(createInferAddressSpacesPass(/* AddressSpace= */ 0));
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Naghasan wrote:

The pass can call `TargetTransformInfo::getFlatAddressSpace()` to get the address space used as flat, so it would make sense to implement `SPIRVTTIImpl::getFlatAddressSpace()` for this and make it compatible with compute (which would use 4 in this case). There is other passes in LLVM that could use this information as well.

I'm saying this while not knowing much about hlsl.

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