[llvm] [AMDGPU] Add iglp_opt(2) to provide initial MFMA/Exp interleaving (PR #80370)

[Matt Arsenault via llvm-commits]

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@@ -904,6 +909,854 @@ void MFMASmallGemmOpt::applyIGLPStrategy(
   }
 }
 
+class MFMAExpInterleaveOpt final : public IGLPStrategy {
+private:
+  /// Whether or not the instruction is a transitive predecessor of an MFMA
+  /// instruction
+  class IsPipeExp final : public InstructionRule {
+  public:
+    bool apply(const SUnit *SU, const ArrayRef<SUnit *> Collection,
+               SmallVectorImpl<SchedGroup> &SyncPipe) override {
+
+      auto DAG = SyncPipe[0].DAG;
+      auto TII = SyncPipe[0].TII;
+
+      if (Cache->empty()) {
+        auto I = DAG->SUnits.rbegin();
+        auto E = DAG->SUnits.rend();
+        for (; I != E; I++) {
+          if (TII->isMFMAorWMMA(*(I->getInstr())))
+            Cache->push_back(&*I);
+        }
+      }
+
+      if (Cache->empty())
+        return false;
+
+      auto Reaches = (std::any_of(
+          Cache->begin(), Cache->end(), [&SU, &DAG](SUnit *TargetSU) {
+            return DAG->IsReachable(TargetSU, const_cast<SUnit *>(SU));
+          }));
+
+      return Reaches;
+    }
+    IsPipeExp(const SIInstrInfo *TII, unsigned SGID, bool NeedsCache = false)
+        : InstructionRule(TII, SGID, NeedsCache) {}
+  };
+
+  /// Whether or not the insturction is a transitive predecessor of the same
+  /// MFMA instruction as an instruction in a SchedGroup \p Number steps before
+  class ProduceSameMFMAWithPrevN final : public InstructionRule {
+  private:
+    unsigned Number = 1;
+
+  public:
+    bool apply(const SUnit *SU, const ArrayRef<SUnit *> Collection,
+               SmallVectorImpl<SchedGroup> &SyncPipe) override {
+      SchedGroup *OtherGroup = nullptr;
+      for (auto &PipeSG : SyncPipe) {
+        if ((unsigned)PipeSG.getSGID() == SGID - Number) {
+          OtherGroup = &PipeSG;
+        }
+      }
+
+      if (!OtherGroup)
+        return false;
+      if (!OtherGroup->Collection.size())
+        return true;
+
+      auto DAG = SyncPipe[0].DAG;
+
+      if (Cache->empty()) {
+        auto TII = SyncPipe[0].TII;
+        SmallVector<SUnit *, 8> Worklist;
+
+        auto I = DAG->SUnits.rbegin();
+        auto E = DAG->SUnits.rend();
+        for (; I != E; I++)
+          if (TII->isMFMAorWMMA(*(I->getInstr())))
+            Worklist.push_back(&*I);
+
+        for (auto BaseSU : OtherGroup->Collection) {
+          if (!Cache->empty())
+            break;
+          for (auto CandSU : Worklist) {
+            if (DAG->IsReachable(CandSU, BaseSU)) {
+              Cache->push_back(CandSU);
+              break;
+            }
+          }
+        }
+      }
+      if (Cache->empty())
+        return false;
+
+      return DAG->IsReachable((*Cache)[0], const_cast<SUnit *>(SU));
+    }
+
+    ProduceSameMFMAWithPrevN(unsigned Number, const SIInstrInfo *TII,
+                             unsigned SGID, bool NeedsCache = false)
+        : InstructionRule(TII, SGID, NeedsCache), Number(Number) {}
+  };
+
+  /// Whether or not the instruction has less than \p Size immediate successors
+  class LessThanNSuccs final : public InstructionRule {
+  private:
+    unsigned Size = 1;
+
+  public:
+    bool apply(const SUnit *SU, const ArrayRef<SUnit *> Collection,
+               SmallVectorImpl<SchedGroup> &SyncPipe) override {
+      if (!SyncPipe.size())
+        return false;
+
+      return SU->Succs.size() < Size;
+    }
+    LessThanNSuccs(unsigned Size, const SIInstrInfo *TII, unsigned SGID,
+                   bool NeedsCache = false)
+        : InstructionRule(TII, SGID, NeedsCache), Size(Size) {}
+  };
+
+  // Whether or not the instruction is an V_CVT instruction.
+  class IsCvt final : public InstructionRule {
+  private:
+  public:
+    bool apply(const SUnit *SU, const ArrayRef<SUnit *> Collection,
+               SmallVectorImpl<SchedGroup> &SyncPipe) override {
+      auto Opc = SU->getInstr()->getOpcode();
+      return Opc == AMDGPU::V_CVT_F16_F32_e32 ||
+             Opc == AMDGPU::V_CVT_F16_F32_e32_gfx10 ||
+             Opc == AMDGPU::V_CVT_I32_F32_e32 ||
+             Opc == AMDGPU::V_CVT_I32_F32_e32_gfx10 ||
+             Opc == AMDGPU::V_CVT_I32_F32_e32_gfx11;
+    }
+    IsCvt(const SIInstrInfo *TII, unsigned SGID, bool NeedsCache = false)
+        : InstructionRule(TII, SGID, NeedsCache) {}
+  };
+
+  // Whether or not the instruction is an V_FMA_F32 instruction.
+  class IsFMA final : public InstructionRule {
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arsenm wrote:

But why?

https://github.com/llvm/llvm-project/pull/80370