[llvm] [AMDGPU][SIInsertWaitcnts] Do not add s_waitcnt when the counters are known to be 0 already (PR #72830)

[via llvm-commits]

Juan Manuel MARTINEZ =?utf-8?q?CAAMAÑO?= <juamarti at amd.com>
Message-ID:
In-Reply-To: <llvm.org/llvm/llvm-project/pull/72830 at github.com>


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@@ -1464,6 +1464,21 @@ def S_WAKEUP : SOPP_Pseudo <"s_wakeup", (ins) > {
 
 def S_WAITCNT : SOPP_Pseudo <"s_waitcnt" , (ins SWaitCnt:$simm16), "$simm16",
     [(int_amdgcn_s_waitcnt timm:$simm16)]>;
+
+// "_soft" waitcnts are waitcnts that are either relaxed into their non-soft
+// counterpart, or completely removed.
+//
+// These are inserted by to resolve memory dependencies by the memory
+// legalizer and later optimized by SIInsertWaitcnts
+// For example, a S_WAITCNT_soft 0 can be completely removed on a function
+// that doesn't access memory.
+def S_WAITCNT_soft : SOPP_Pseudo <"s_soft_waitcnt" , (ins SWaitCnt:$simm16), "$simm16">;
+def S_WAITCNT_VSCNT_soft : SOPP_Pseudo<"s_soft_waitcnt_vscnt", (ins SReg_32:$sdst, s16imm:$simm16), "$sdst, $simm16"> {
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rovka wrote:

Why isn't this a `SOPK_WAITCNT`, like `S_WAITCNT_VSCNT`?

https://github.com/llvm/llvm-project/pull/72830