[llvm] AMDGPU: Drop and upgrade llvm.amdgcn.atomic.csub/cond.sub to atomicrmw (PR #105553)

[Matt Arsenault via llvm-commits]

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@@ -1150,7 +1150,15 @@ Value *SplitPtrStructs::handleMemoryInst(Instruction *I, Value *Arg, Value *Ptr,
     case AtomicRMWInst::UIncWrap:
     case AtomicRMWInst::UDecWrap:
       report_fatal_error("wrapping increment/decrement not supported for "
-                         "buffer resources and should've ben expanded away");
+                         "buffer resources and should've been expanded away");
+      break;
+    case AtomicRMWInst::USubCond:
+      report_fatal_error("conditional subtract not supported for buffer "
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arsenm wrote:

I see BUFFER_ATOMIC_CSUB_U32 in the manual? 

https://github.com/llvm/llvm-project/pull/105553