[LazyMachineBFI] Reimplement with getAnalysisIfAvailable

Since LoopInfo is not available in machine passes as universally as in IR
passes, using the same approach for OptimizationRemarkEmitter as we did for IR
will run LoopInfo and DominatorTree unnecessarily.  (LoopInfo is not used
lazily by ORE.)

To fix this, I am modifying the approach I took in D29836.  LazyMachineBFI now
uses its client passes including MachineBFI itself that are available or
otherwise compute them on the fly.

So for example GreedyRegAlloc, since it's already using MBFI, will reuse that
instance.  On the other hand, AsmPrinter in Justin's patch will generate DT,
LI and finally BFI on the fly.

(I am of course wondering now if the simplicity of this approach is even
preferable in IR.  I will do some experiments.)

Testing is provided by an updated version of D29837 which requires Justin's
patch to bring ORE to the AsmPrinter.

Differential Revision: https://reviews.llvm.org/D30128

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@295996 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/CodeGen/LazyMachineBlockFrequencyInfo.h b/include/llvm/CodeGen/LazyMachineBlockFrequencyInfo.h
index 041b96db35f27cf81d505b930fb9dcbdd2e44b3a..848ee1dc0dc6013ca49999e40afc1339d0e0a042 100644 (file)
--- a/include/llvm/CodeGen/LazyMachineBlockFrequencyInfo.h
+++ b/include/llvm/CodeGen/LazyMachineBlockFrequencyInfo.h
@@ -17,9 +17,9 @@
 #ifndef LLVM_ANALYSIS_LAZYMACHINEBLOCKFREQUENCYINFO_H
 #define LLVM_ANALYSIS_LAZYMACHINEBLOCKFREQUENCYINFO_H
 
-#include "llvm/Analysis/LazyBlockFrequencyInfo.h"
 #include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
 #include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
+#include "llvm/CodeGen/MachineDominators.h"
 #include "llvm/CodeGen/MachineLoopInfo.h"
 
 namespace llvm {
@@ -28,30 +28,30 @@ namespace llvm {
 /// computed when the analysis pass is executed but rather when the BFI result
 /// is explicitly requested by the analysis client.
 ///
-/// There are some additional requirements for any client pass that wants to use
-/// the analysis:
-///
-/// 1. The pass needs to initialize dependent passes with:
-///
-///   INITIALIZE_PASS_DEPENDENCY(LazyMachineBFIPass)
-///
-/// 2. Similarly, getAnalysisUsage should call:
-///
-///   LazyMachineBlockFrequencyInfoPass::getLazyMachineBFIAnalysisUsage(AU)
-///
-/// 3. The computed MachineBFI should be requested with
-///    getAnalysis<LazyMachineBlockFrequencyInfoPass>().getBFI() before
-///    MachineLoopInfo could be invalidated for example by changing the CFG.
+/// This works by checking querying if MBFI is available and otherwise
+/// generating MBFI on the fly.  In this case the passes required for (LI, DT)
+/// are also queried before being computed on the fly.
 ///
 /// Note that it is expected that we wouldn't need this functionality for the
 /// new PM since with the new PM, analyses are executed on demand.
 
 class LazyMachineBlockFrequencyInfoPass : public MachineFunctionPass {
 private:
-  /// \brief Machine BPI is an immutable pass, no need to use it lazily.
-  LazyBlockFrequencyInfo<MachineFunction, MachineBranchProbabilityInfo,
-                         MachineLoopInfo, MachineBlockFrequencyInfo>
-      LMBFI;
+  /// If generated on the fly this own the instance.
+  mutable std::unique_ptr<MachineBlockFrequencyInfo> OwnedMBFI;
+
+  /// If generated on the fly this own the instance.
+  mutable std::unique_ptr<MachineLoopInfo> OwnedMLI;
+
+  /// If generated on the fly this own the instance.
+  mutable std::unique_ptr<MachineDominatorTree> OwnedMDT;
+
+  /// The function.
+  MachineFunction *MF = nullptr;
+
+  /// \brief Calculate MBFI and all other analyses that's not available and
+  /// required by BFI.
+  MachineBlockFrequencyInfo &calculateIfNotAvailable() const;
 
 public:
   static char ID;
@@ -59,25 +59,18 @@ public:
   LazyMachineBlockFrequencyInfoPass();
 
   /// \brief Compute and return the block frequencies.
-  MachineBlockFrequencyInfo &getBFI() { return LMBFI.getCalculated(); }
+  MachineBlockFrequencyInfo &getBFI() { return calculateIfNotAvailable(); }
 
   /// \brief Compute and return the block frequencies.
   const MachineBlockFrequencyInfo &getBFI() const {
-    return LMBFI.getCalculated();
+    return calculateIfNotAvailable();
   }
 
   void getAnalysisUsage(AnalysisUsage &AU) const override;
 
-  /// Helper for client passes to set up the analysis usage on behalf of this
-  /// pass.
-  static void getLazyMachineBFIAnalysisUsage(AnalysisUsage &AU);
-
   bool runOnMachineFunction(MachineFunction &F) override;
   void releaseMemory() override;
   void print(raw_ostream &OS, const Module *M) const override;
 };
-
-/// \brief Helper for client passes to initialize dependent passes for LMBFI.
-void initializeLazyMachineBFIPassPass(PassRegistry &Registry);
 }
 #endif

diff --git a/lib/CodeGen/LazyMachineBlockFrequencyInfo.cpp b/lib/CodeGen/LazyMachineBlockFrequencyInfo.cpp
index 34611f8064d76b7fd62b77767db06400e8764d9d..996d40ca6e1eefe51cee58c9a40f928d5eb2d47d 100644 (file)
--- a/lib/CodeGen/LazyMachineBlockFrequencyInfo.cpp
+++ b/lib/CodeGen/LazyMachineBlockFrequencyInfo.cpp
@@ -37,38 +37,61 @@ LazyMachineBlockFrequencyInfoPass::LazyMachineBlockFrequencyInfoPass()
 
 void LazyMachineBlockFrequencyInfoPass::print(raw_ostream &OS,
                                               const Module *M) const {
-  LMBFI.getCalculated().print(OS, M);
+  getBFI().print(OS, M);
 }
 
 void LazyMachineBlockFrequencyInfoPass::getAnalysisUsage(
     AnalysisUsage &AU) const {
   AU.addRequired<MachineBranchProbabilityInfo>();
-  AU.addRequired<MachineLoopInfo>();
   AU.setPreservesAll();
   MachineFunctionPass::getAnalysisUsage(AU);
 }
 
 void LazyMachineBlockFrequencyInfoPass::releaseMemory() {
-  LMBFI.releaseMemory();
+  OwnedMBFI.reset();
+  OwnedMLI.reset();
+  OwnedMDT.reset();
 }
 
-bool LazyMachineBlockFrequencyInfoPass::runOnMachineFunction(
-    MachineFunction &MF) {
-  auto &BPIPass = getAnalysis<MachineBranchProbabilityInfo>();
-  auto &LI = getAnalysis<MachineLoopInfo>();
-  LMBFI.setAnalysis(&MF, &BPIPass, &LI);
-  return false;
-}
+MachineBlockFrequencyInfo &
+LazyMachineBlockFrequencyInfoPass::calculateIfNotAvailable() const {
+  auto *MBFI = getAnalysisIfAvailable<MachineBlockFrequencyInfo>();
+  if (MBFI) {
+    DEBUG(dbgs() << "MachineBlockFrequencyInfo is available\n");
+    return *MBFI;
+  }
 
-void LazyMachineBlockFrequencyInfoPass::getLazyMachineBFIAnalysisUsage(
-    AnalysisUsage &AU) {
-  AU.addRequired<LazyMachineBlockFrequencyInfoPass>();
-  AU.addRequired<MachineBranchProbabilityInfo>();
-  AU.addRequired<MachineLoopInfo>();
+  auto &MBPI = getAnalysis<MachineBranchProbabilityInfo>();
+  auto *MLI = getAnalysisIfAvailable<MachineLoopInfo>();
+  auto *MDT = getAnalysisIfAvailable<MachineDominatorTree>();
+  DEBUG(dbgs() << "Building MachineBlockFrequencyInfo on the fly\n");
+  DEBUG(if (MLI) dbgs() << "LoopInfo is available\n");
+
+  if (!MLI) {
+    DEBUG(dbgs() << "Building LoopInfo on the fly\n");
+    // First create a dominator tree.
+    DEBUG(if (MDT) dbgs() << "DominatorTree is available\n");
+
+    if (!MDT) {
+      DEBUG(dbgs() << "Building DominatorTree on the fly\n");
+      OwnedMDT = make_unique<MachineDominatorTree>();
+      OwnedMDT->getBase().recalculate(*MF);
+      MDT = OwnedMDT.get();
+    }
+
+    // Generate LoopInfo from it.
+    OwnedMLI = make_unique<MachineLoopInfo>();
+    OwnedMLI->getBase().analyze(MDT->getBase());
+    MLI = OwnedMLI.get();
+  }
+
+  OwnedMBFI = make_unique<MachineBlockFrequencyInfo>();
+  OwnedMBFI->calculate(*MF, MBPI, *MLI);
+  return *OwnedMBFI.get();
 }
 
-void llvm::initializeLazyMachineBFIPassPass(PassRegistry &Registry) {
-  INITIALIZE_PASS_DEPENDENCY(LazyMachineBlockFrequencyInfoPass);
-  INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfo);
-  INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo);
+bool LazyMachineBlockFrequencyInfoPass::runOnMachineFunction(
+    MachineFunction &F) {
+  MF = &F;
+  return false;
 }

diff --git a/lib/CodeGen/MachineOptimizationRemarkEmitter.cpp b/lib/CodeGen/MachineOptimizationRemarkEmitter.cpp
index b76e75a4bd4d0a1edbea35b2a71176b6456c87df..b226135f8f737847200487e4154cb2ab140b48a4 100644 (file)
--- a/lib/CodeGen/MachineOptimizationRemarkEmitter.cpp
+++ b/lib/CodeGen/MachineOptimizationRemarkEmitter.cpp
@@ -74,7 +74,7 @@ bool MachineOptimizationRemarkEmitterPass::runOnMachineFunction(
 
 void MachineOptimizationRemarkEmitterPass::getAnalysisUsage(
     AnalysisUsage &AU) const {
-  LazyMachineBlockFrequencyInfoPass::getLazyMachineBFIAnalysisUsage(AU);
+  AU.addRequired<LazyMachineBlockFrequencyInfoPass>();
   AU.setPreservesAll();
   MachineFunctionPass::getAnalysisUsage(AU);
 }
@@ -85,6 +85,6 @@ static const char ore_name[] = "Machine Optimization Remark Emitter";
 
 INITIALIZE_PASS_BEGIN(MachineOptimizationRemarkEmitterPass, ORE_NAME, ore_name,
                       false, true)
-INITIALIZE_PASS_DEPENDENCY(LazyMachineBFIPass)
+INITIALIZE_PASS_DEPENDENCY(LazyMachineBlockFrequencyInfoPass)
 INITIALIZE_PASS_END(MachineOptimizationRemarkEmitterPass, ORE_NAME, ore_name,
                     false, true)