[clang] [llvm] [AMDGPU] Add target intrinsic for s_buffer_prefetch_data (PR #107293)

[Matt Arsenault via cfe-commits]

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@@ -9934,6 +9934,12 @@ SDValue SITargetLowering::LowerINTRINSIC_VOID(SDValue Op,
     auto NewMI = DAG.getMachineNode(Opc, DL, Op->getVTList(), Ops);
     return SDValue(NewMI, 0);
   }
+  case Intrinsic::amdgcn_s_prefetch_data: {
+    // For non-global address space preserve the chain and remove the call.
+    if (!AMDGPU::isFlatGlobalAddrSpace(cast<MemSDNode>(Op)->getAddressSpace()))
+      return Op.getOperand(0);
+    return Op;
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arsenm wrote:

I'd expect the private/local cases to be an error. Also collectFlatAddressOperands should handle this, to get the flat->global optimization in InferAddressSpaces 

https://github.com/llvm/llvm-project/pull/107293