[llvm] [AMDGPU] Optimize LDS DMA soft waitcnt (PR #138802)

[Jay Foad via llvm-commits]

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@@ -1608,6 +1608,7 @@ let OtherPredicates = [HasImageInsts] in {
   def S_WAIT_DSCNT_soft : SOPP_Pseudo <"s_soft_wait_dscnt", (ins s16imm:$simm16), "$simm16">;
   def S_WAIT_KMCNT_soft : SOPP_Pseudo <"s_soft_wait_kmcnt", (ins s16imm:$simm16), "$simm16">;
 }
+def S_WAITCNT_VMCNT_LDS_DMA_soft : SOPP_Pseudo <"s_soft_waitcnt" , (ins SWaitCnt:$simm16), "$simm16">;
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jayfoad wrote:

Yes please! What is it? How does it interact with S_WAITCNT_VMCNT? Why does SIMemoryLegalizer want to start emitting it?

https://github.com/llvm/llvm-project/pull/138802