[flang] [libcxx] [compiler-rt] [llvm] [libc] [lldb] [lld] [clang-tools-extra] [clang] [AMDGPU] Use alias info to relax waitcounts for LDS DMA (PR #74537)

[Stanislav Mekhanoshin via cfe-commits]

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@@ -1183,9 +1228,21 @@ bool SIInsertWaitcnts::generateWaitcntInstBefore(MachineInstr &MI,
         // No need to wait before load from VMEM to LDS.
         if (TII->mayWriteLDSThroughDMA(MI))
           continue;
-        unsigned RegNo = SQ_MAX_PGM_VGPRS + EXTRA_VGPR_LDS;
+
         // VM_CNT is only relevant to vgpr or LDS.
-        ScoreBrackets.determineWait(VM_CNT, RegNo, Wait);
+        unsigned RegNo = SQ_MAX_PGM_VGPRS + EXTRA_VGPR_LDS;
+        bool FoundAliasingStore = false;
+        if (Ptr && Memop->getAAInfo() && Memop->getAAInfo().Scope) {
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rampitec wrote:

I have reserved just 8 pseudo registers to track it. I do not want to fill it with unrelated stuff. I know that the only way AA will be able to handle this very specific situation is if there is scope info, otherwise there is no reason to waste a slot and compile time. If I do not enter this 'if' the pass will just do conservatively correct thing and wait for this memory regardless of aliasing or lack of it.

https://github.com/llvm/llvm-project/pull/74537