[AMDGPU] Remove scope check in SIInsertWaitcnts::generateWaitcntInstB… (llvm#4380)

Author: Salinas, David

llvm/lib/Target/AMDGPU/SIInsertWaitcnts.cpp

@@ -1918,13 +1918,7 @@ bool SIInsertWaitcnts::generateWaitcntInstBefore(MachineInstr &MI,
 
         // LOAD_CNT is only relevant to vgpr or LDS.
         unsigned RegNo = FIRST_LDS_VGPR;
-        // Only objects with alias scope info were added to LDSDMAScopes array.
-        // In the absense of the scope info we will not be able to disambiguate
-        // aliasing here. There is no need to try searching for a corresponding
-        // store slot. This is conservatively correct because in that case we
-        // will produce a wait using the first (general) LDS DMA wait slot which
-        // will wait on all of them anyway.
-        if (Ptr && Memop->getAAInfo() && Memop->getAAInfo().Scope) {
+        if (Ptr && Memop->getAAInfo()) {
           const auto &LDSDMAStores = ScoreBrackets.getLDSDMAStores();
           for (unsigned I = 0, E = LDSDMAStores.size(); I != E; ++I) {
             if (MI.mayAlias(AA, *LDSDMAStores[I], true))

llvm/test/CodeGen/AMDGPU/waitcnt-unscoped.ll

@@ -26,7 +26,6 @@ define amdgpu_kernel void @test_waitcnt(ptr addrspace(1) %global_buffer, ptr add
 ; CHECK-NEXT:    ds_write_b32 v2, v1
 ; CHECK-NEXT:    ds_write_b32 v3, v1
 ; CHECK-NEXT:    ; sched_barrier mask(0x00000000)
-; CHECK-NEXT:    s_waitcnt vmcnt(0)
 ; CHECK-NEXT:    ds_read_b32 v2, v2
 ; CHECK-NEXT:    s_waitcnt lgkmcnt(0)
 ; CHECK-NEXT:    global_store_dword v0, v2, s[0:1] offset:16