[llvm] [AMDGPU] Use alias analysis for SMEM/VMEM WAR waitcnts (PR #206569)

[Jay Foad via llvm-commits]

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@@ -2418,18 +2419,37 @@ bool SIInsertWaitcnts::generateWaitcntInstBefore(
       // instruction to guarantee the right WAW order.
       // 2) If a destination operand that was used by a recent export/store ins,
       // add s_waitcnt on exp_cnt to guarantee the WAR order.
-
+      bool CheckedPendingSMRDLoads = false;
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jayfoad wrote:

IIUC this flag only saves compile time if we see a VMEM with more than one store MMO, which probably never happens? But I guess it doesn't hurt.

https://github.com/llvm/llvm-project/pull/206569