[llvm] [AMDGPU] IGLP: Fix static variables (PR #137549)

[Robert Imschweiler via llvm-commits]

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@@ -1353,17 +1344,25 @@ bool MFMAExpInterleaveOpt::analyzeDAG(const SIInstrInfo *TII) {
 
   auto isAdd = [](unsigned Opc) { return Opc == AMDGPU::V_ADD_F32_e32; };
 
+  // Heuristic helper function (see below)
+  auto IsFMACDataDep = [](SDep &Dep) {
+    return Dep.getKind() == SDep::Kind::Data &&
+           Dep.getSUnit()->getInstr()->getOpcode() == AMDGPU::V_FMAC_F32_e32;
+  };
+
   AddPipeCount = 0;
   for (SUnit &SU : DAG->SUnits) {
     auto Opc = SU.getInstr()->getOpcode();
     if (TII->isTRANS(Opc)) {
       // Avoid counting a potential bonus V_EXP which all the MFMA depend on
-      if (SU.Succs.size() >= 7)
+      // FIXME: This heuristic needs improvement/clarification!
+      // In general, the pipeline seems to look like this:
+      //   fma_f32 -> exp_f32 -> cvt_f16_f32 -> v_pack_b32_f16 -> mfma_.._f16
+      //   (with potential arithmetic between exp and cvt)
+      //   see
+      //   https://github.com/llvm/llvm-project/pull/80370#discussion_r1483660378
+      if (SU.Succs.size() >= 7 && any_of(SU.Succs, IsFMACDataDep))
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ro-i wrote:

So please let me know if there is a better way to detect the additional EXP (also in post-ra)

https://github.com/llvm/llvm-project/pull/137549