[llvm] [AMDGPU] Add legalization rules for atomic ops (PR #175253)

[Petar Avramovic via llvm-commits]

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@@ -664,6 +664,17 @@ RegBankLegalizeRules::RegBankLegalizeRules(const GCNSubtarget &_ST,
       .Uni(S64, {{Sgpr64}, {Sgpr64, Imm}})
       .Div(S64, {{Vgpr64}, {Vgpr64, Imm}});
 
+  // Atomic read-modify-write operations: result and value are always VGPR,
+  // pointer varies by address space.
+  addRulesForGOpcs({G_ATOMICRMW_ADD, G_ATOMICRMW_SUB, G_ATOMICRMW_XCHG,
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petar-avramovic wrote:

can you add some ll tests for remaining opcodes (there are some for add and sub)

https://github.com/llvm/llvm-project/pull/175253