[llvm] [AMDGPU] Add initial version of gfx950 MFMA co-exec rules (PR #214682)

[Matt Arsenault via llvm-commits]

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@@ -346,12 +346,180 @@ inline CoExecInfo CoExecInfo::build(unsigned TotalWindow, const char *Pattern) {
   return Info;
 }
 
+/// Get co-execution info for a gfx950 MFMA instruction.
+/// The occupancy (cycles until the next MFMA may issue) is expressed as the
+/// first stage carrying the WMMA bit.
+inline CoExecInfo getMFMACoExecInfo(const MachineInstr &MI) {
+  CoExecInfo Res;
+  for (unsigned I = 0; I < MaxCoExecStages; ++I)
+    Res.Slots[I].Mask = CoExecMask::None;
+
+  // TODO: Implement proper patterns support (for debugging purposes).
+  // Existing pattern letters are WMMA-specific and will probably be confusing
+  // if used as-is for MFMA. Inventing new MFMA-specific letters is an option,
+  // but perhaps the pattern should be instead dynamically reconstructed when
+  // needed by printing specific slots in full instead of a key for them.
+  Res.Pattern = "undefinedundefinedundefinedundefined";
+
+  // MFMA co-exec slots are incremental, i.e. for every slot N it supports all
+  // instructions which were supported by the previous slot N-1 and may support
+  // something extra.
+  auto AllowCoExec = [](CoExecInfo &Info, CoExecMaskT ExtraBits,
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arsenm wrote:

Move to helper, nothing is captured 

https://github.com/llvm/llvm-project/pull/214682