[clang] [llvm] [AMDGPU] Emit a waitcnt instruction after each memory instruction (PR #79236)

[Jay Foad via cfe-commits]

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@@ -2326,6 +2326,20 @@ bool SIInsertWaitcnts::insertWaitcntInBlock(MachineFunction &MF,
     }
 #endif
 
+    if (ST->isPreciseMemoryEnabled() && Inst.mayLoadOrStore()) {
+      AMDGPU::Waitcnt Wait;
+      if (ST->hasExtendedWaitCounts())
+        Wait = AMDGPU::Waitcnt(0, 0, 0, 0, 0, 0, 0);
+      else
+        Wait = AMDGPU::Waitcnt(0, 0, 0, 0);
+
+      if (!Inst.mayStore())
+        Wait.StoreCnt = ~0u;
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jayfoad wrote:

GFX10 introduced a separate counter for **VMEM** stores with the name VScnt. GFX12 just renamed it to STOREcnt. No architecture has a separate store counter for DS or SMEM. So `ds_add_u32 v0, v1` followed by `s_waitcnt lgkmcnt(0)` (pre-GFX12) or `s_wait_dscnt 0` (GFX12) is fine .

https://github.com/llvm/llvm-project/pull/79236