Recommit rL305677: [CodeGen] Add generic MacroFusion pass
Use llvm::make_unique to avoid ambiguity with MSVC.
This patch adds a generic MacroFusion pass, that is used on X86 and
AArch64, which both define target-specific shouldScheduleAdjacent
functions. This generic pass should make it easier for other targets to
implement macro fusion and I intend to add macro fusion for ARM shortly.
Differential Revision: https://reviews.llvm.org/D34144
llvm-svn: 305690
diff --git a/llvm/lib/CodeGen/CMakeLists.txt b/llvm/lib/CodeGen/CMakeLists.txt
index 55a27e2f..7f3c6da 100644
--- a/llvm/lib/CodeGen/CMakeLists.txt
+++ b/llvm/lib/CodeGen/CMakeLists.txt
@@ -92,6 +92,7 @@
PatchableFunction.cpp
MIRPrinter.cpp
MIRPrintingPass.cpp
+ MacroFusion.cpp
OptimizePHIs.cpp
ParallelCG.cpp
PeepholeOptimizer.cpp
diff --git a/llvm/lib/CodeGen/MacroFusion.cpp b/llvm/lib/CodeGen/MacroFusion.cpp
new file mode 100644
index 0000000..45ea0e4
--- /dev/null
+++ b/llvm/lib/CodeGen/MacroFusion.cpp
@@ -0,0 +1,150 @@
+//===- MacroFusion.cpp - Macro Fusion ----------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+/// \file This file contains the implementation of the DAG scheduling mutation
+/// to pair instructions back to back.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/MacroFusion.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Target/TargetInstrInfo.h"
+
+#define DEBUG_TYPE "misched"
+
+STATISTIC(NumFused, "Number of instr pairs fused");
+
+using namespace llvm;
+
+static cl::opt<bool> EnableMacroFusion("misched-fusion", cl::Hidden,
+ cl::desc("Enable scheduling for macro fusion."), cl::init(true));
+
+namespace {
+
+static void fuseInstructionPair(ScheduleDAGMI &DAG, SUnit &FirstSU,
+ SUnit &SecondSU) {
+ // Create a single weak edge between the adjacent instrs. The only effect is
+ // to cause bottom-up scheduling to heavily prioritize the clustered instrs.
+ DAG.addEdge(&SecondSU, SDep(&FirstSU, SDep::Cluster));
+
+ // Adjust the latency between the anchor instr and its
+ // predecessors.
+ for (SDep &IDep : SecondSU.Preds)
+ if (IDep.getSUnit() == &FirstSU)
+ IDep.setLatency(0);
+
+ // Adjust the latency between the dependent instr and its
+ // predecessors.
+ for (SDep &IDep : FirstSU.Succs)
+ if (IDep.getSUnit() == &SecondSU)
+ IDep.setLatency(0);
+
+ DEBUG(dbgs() << DAG.MF.getName() << "(): Macro fuse ";
+ FirstSU.print(dbgs(), &DAG); dbgs() << " - ";
+ SecondSU.print(dbgs(), &DAG); dbgs() << " / ";
+ dbgs() << DAG.TII->getName(FirstSU.getInstr()->getOpcode()) << " - " <<
+ DAG.TII->getName(SecondSU.getInstr()->getOpcode()) << '\n'; );
+
+ if (&SecondSU != &DAG.ExitSU)
+ // Make instructions dependent on FirstSU also dependent on SecondSU to
+ // prevent them from being scheduled between FirstSU and and SecondSU.
+ for (const SDep &SI : FirstSU.Succs) {
+ if (SI.getSUnit() == &SecondSU)
+ continue;
+ DEBUG(dbgs() << " Copy Succ ";
+ SI.getSUnit()->print(dbgs(), &DAG); dbgs() << '\n';);
+ DAG.addEdge(SI.getSUnit(), SDep(&SecondSU, SDep::Artificial));
+ }
+
+ ++NumFused;
+}
+
+
+/// \brief Post-process the DAG to create cluster edges between instrs that may
+/// be fused by the processor into a single operation.
+class MacroFusion : public ScheduleDAGMutation {
+ ShouldSchedulePredTy shouldScheduleAdjacent;
+ bool FuseBlock;
+ bool scheduleAdjacentImpl(ScheduleDAGMI &DAG, SUnit &AnchorSU);
+
+public:
+ MacroFusion(ShouldSchedulePredTy shouldScheduleAdjacent, bool FuseBlock)
+ : shouldScheduleAdjacent(shouldScheduleAdjacent), FuseBlock(FuseBlock) {}
+
+ void apply(ScheduleDAGInstrs *DAGInstrs) override;
+};
+
+void MacroFusion::apply(ScheduleDAGInstrs *DAGInstrs) {
+ ScheduleDAGMI *DAG = static_cast<ScheduleDAGMI*>(DAGInstrs);
+
+ if (FuseBlock)
+ // For each of the SUnits in the scheduling block, try to fuse the instr in
+ // it with one in its predecessors.
+ for (SUnit &ISU : DAG->SUnits)
+ scheduleAdjacentImpl(*DAG, ISU);
+
+ if (DAG->ExitSU.getInstr())
+ // Try to fuse the instr in the ExitSU with one in its predecessors.
+ scheduleAdjacentImpl(*DAG, DAG->ExitSU);
+}
+
+/// \brief Implement the fusion of instr pairs in the scheduling DAG,
+/// anchored at the instr in AnchorSU..
+bool MacroFusion::scheduleAdjacentImpl(ScheduleDAGMI &DAG, SUnit &AnchorSU) {
+ const MachineInstr &AnchorMI = *AnchorSU.getInstr();
+ const TargetInstrInfo &TII = *DAG.TII;
+ const TargetSubtargetInfo &ST = DAG.MF.getSubtarget();
+
+ // Check if the anchor instr may be fused.
+ if (!shouldScheduleAdjacent(TII, ST, nullptr, AnchorMI))
+ return false;
+
+ // Explorer for fusion candidates among the dependencies of the anchor instr.
+ for (SDep &Dep : AnchorSU.Preds) {
+ // Ignore dependencies that don't enforce ordering.
+ if (Dep.getKind() == SDep::Anti || Dep.getKind() == SDep::Output ||
+ Dep.isWeak())
+ continue;
+
+ SUnit &DepSU = *Dep.getSUnit();
+ if (DepSU.isBoundaryNode())
+ continue;
+
+ const MachineInstr *DepMI = DepSU.getInstr();
+ if (!shouldScheduleAdjacent(TII, ST, DepMI, AnchorMI))
+ continue;
+
+ fuseInstructionPair(DAG, DepSU, AnchorSU);
+ return true;
+ }
+
+ return false;
+}
+
+} // end anonymous namespace
+
+
+namespace llvm {
+
+std::unique_ptr<ScheduleDAGMutation>
+createMacroFusionDAGMutation(ShouldSchedulePredTy shouldScheduleAdjacent) {
+ if(EnableMacroFusion)
+ return llvm::make_unique<MacroFusion>(shouldScheduleAdjacent, true);
+ return nullptr;
+}
+
+std::unique_ptr<ScheduleDAGMutation>
+createBranchMacroFusionDAGMutation(ShouldSchedulePredTy shouldScheduleAdjacent) {
+ if(EnableMacroFusion)
+ return llvm::make_unique<MacroFusion>(shouldScheduleAdjacent, false);
+ return nullptr;
+}
+
+} // end namespace llvm