Remove MachineLoopInfo dependency from AsmPrinter.

Summary:
Currently MachineLoopInfo is used in only two places:
1) for computing IsBasicBlockInsideInnermostLoop field of MCCodePaddingContext, and it is never used.
2) in emitBasicBlockLoopComments, which is called only if `isVerbose()` is true.
Despite that, we currently have a dependency on MachineLoopInfo, which makes
pass manager to compute it and MachineDominator Tree. This patch removes the
use (1) and makes the use (2) lazy, thus avoiding some redundant
recomputations.

Reviewers: opaparo, gadi.haber, rafael, craig.topper, zvi

Subscribers: rengolin, javed.absar, hiraditya, llvm-commits

Differential Revision: https://reviews.llvm.org/D44812

llvm-svn: 329542

llvm/include/llvm/CodeGen/AsmPrinter.h

@@ -50,6 +50,7 @@ class GlobalValue;
 class GlobalVariable;
 class MachineBasicBlock;
 class MachineConstantPoolValue;
+class MachineDominatorTree;
 class MachineFunction;
 class MachineInstr;
 class MachineJumpTableInfo;
@@ -92,11 +93,17 @@ class AsmPrinter : public MachineFunctionPass {
   std::unique_ptr<MCStreamer> OutStreamer;
 
   /// The current machine function.
-  const MachineFunction *MF = nullptr;
+  MachineFunction *MF = nullptr;
 
   /// This is a pointer to the current MachineModuleInfo.
   MachineModuleInfo *MMI = nullptr;
 
+  /// This is a pointer to the current MachineLoopInfo.
+  MachineDominatorTree *MDT = nullptr;
+
+  /// This is a pointer to the current MachineLoopInfo.
+  MachineLoopInfo *MLI = nullptr;
+
   /// Optimization remark emitter.
   MachineOptimizationRemarkEmitter *ORE;
 
@@ -130,9 +137,6 @@ class AsmPrinter : public MachineFunctionPass {
 
   static char ID;
 
-  /// If VerboseAsm is set, a pointer to the loop info for this function.
-  MachineLoopInfo *LI = nullptr;
-
   struct HandlerInfo {
     AsmPrinterHandler *Handler;
     const char *TimerName;
@@ -161,6 +165,12 @@ class AsmPrinter : public MachineFunctionPass {
   };
 
 private:
+  /// If generated on the fly this own the instance.
+  std::unique_ptr<MachineDominatorTree> OwnedMDT;
+
+  /// If generated on the fly this own the instance.
+  std::unique_ptr<MachineLoopInfo> OwnedMLI;
+
   /// Structure for generating diagnostics for inline assembly. Only initialised
   /// when necessary.
   mutable std::unique_ptr<SrcMgrDiagInfo> DiagInfo;

llvm/include/llvm/MC/MCCodePadder.h

@@ -28,7 +28,6 @@ typedef SmallVector<const MCPaddingFragment *, 8> MCPFRange;
 
 struct MCCodePaddingContext {
   bool IsPaddingActive;
-  bool IsBasicBlockInsideInnermostLoop;
   bool IsBasicBlockReachableViaFallthrough;
   bool IsBasicBlockReachableViaBranch;
 };

llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -39,6 +39,7 @@
 #include "llvm/CodeGen/GCStrategy.h"
 #include "llvm/CodeGen/MachineBasicBlock.h"
 #include "llvm/CodeGen/MachineConstantPool.h"
+#include "llvm/CodeGen/MachineDominators.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
@@ -238,7 +239,6 @@ void AsmPrinter::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.addRequired<MachineModuleInfo>();
   AU.addRequired<MachineOptimizationRemarkEmitterPass>();
   AU.addRequired<GCModuleInfo>();
-  AU.addRequired<MachineLoopInfo>();
 }
 
 bool AsmPrinter::doInitialization(Module &M) {
@@ -1009,6 +1009,24 @@ void AsmPrinter::EmitFunctionBody() {
 
   bool ShouldPrintDebugScopes = MMI->hasDebugInfo();
 
+  if (isVerbose()) {
+    // Get MachineDominatorTree or compute it on the fly if it's unavailable
+    MDT = getAnalysisIfAvailable<MachineDominatorTree>();
+    if (!MDT) {
+      OwnedMDT = make_unique<MachineDominatorTree>();
+      OwnedMDT->getBase().recalculate(*MF);
+      MDT = OwnedMDT.get();
+    }
+
+    // Get MachineLoopInfo or compute it on the fly if it's unavailable
+    MLI = getAnalysisIfAvailable<MachineLoopInfo>();
+    if (!MLI) {
+      OwnedMLI = make_unique<MachineLoopInfo>();
+      OwnedMLI->getBase().analyze(MDT->getBase());
+      MLI = OwnedMLI.get();
+    }
+  }
+
   // Print out code for the function.
   bool HasAnyRealCode = false;
   int NumInstsInFunction = 0;
@@ -1489,6 +1507,8 @@ bool AsmPrinter::doFinalization(Module &M) {
 
   OutStreamer->Finish();
   OutStreamer->reset();
+  OwnedMLI.reset();
+  OwnedMDT.reset();
 
   return false;
 }
@@ -1515,7 +1535,6 @@ void AsmPrinter::SetupMachineFunction(MachineFunction &MF) {
   }
 
   ORE = &getAnalysis<MachineOptimizationRemarkEmitterPass>().getORE();
-  LI = &getAnalysis<MachineLoopInfo>();
 
   const TargetSubtargetInfo &STI = MF.getSubtarget();
   EnablePrintSchedInfo = PrintSchedule.getNumOccurrences()
@@ -2697,13 +2716,9 @@ static void emitBasicBlockLoopComments(const MachineBasicBlock &MBB,
 void AsmPrinter::setupCodePaddingContext(const MachineBasicBlock &MBB,
                                          MCCodePaddingContext &Context) const {
   assert(MF != nullptr && "Machine function must be valid");
-  assert(LI != nullptr && "Loop info must be valid");
   Context.IsPaddingActive = !MF->hasInlineAsm() &&
                             !MF->getFunction().optForSize() &&
                             TM.getOptLevel() != CodeGenOpt::None;
-  const MachineLoop *CurrentLoop = LI->getLoopFor(&MBB);
-  Context.IsBasicBlockInsideInnermostLoop =
-      CurrentLoop != nullptr && CurrentLoop->getSubLoops().empty();
   Context.IsBasicBlockReachableViaFallthrough =
       std::find(MBB.pred_begin(), MBB.pred_end(), MBB.getPrevNode()) !=
       MBB.pred_end();
@@ -2755,7 +2770,9 @@ void AsmPrinter::EmitBasicBlockStart(const MachineBasicBlock &MBB) const {
         OutStreamer->GetCommentOS() << '\n';
       }
     }
-    emitBasicBlockLoopComments(MBB, LI, *this);
+
+    assert(MLI != nullptr && "MachineLoopInfo should has been computed");
+    emitBasicBlockLoopComments(MBB, MLI, *this);
   }
 
   // Print the main label for the block.

llvm/test/CodeGen/AArch64/O0-pipeline.ll

@@ -59,8 +59,6 @@
 ; CHECK-NEXT:       Implement the 'patchable-function' attribute
 ; CHECK-NEXT:       Lazy Machine Block Frequency Analysis
 ; CHECK-NEXT:       Machine Optimization Remark Emitter
-; CHECK-NEXT:       MachineDominator Tree Construction
-; CHECK-NEXT:       Machine Natural Loop Construction
 ; CHECK-NEXT:       AArch64 Assembly Printer
 ; CHECK-NEXT:       Free MachineFunction
 

llvm/test/CodeGen/AArch64/O3-pipeline.ll

@@ -156,8 +156,6 @@
 ; CHECK-NEXT:       Implement the 'patchable-function' attribute
 ; CHECK-NEXT:       Lazy Machine Block Frequency Analysis
 ; CHECK-NEXT:       Machine Optimization Remark Emitter
-; CHECK-NEXT:       MachineDominator Tree Construction
-; CHECK-NEXT:       Machine Natural Loop Construction
 ; CHECK-NEXT:       AArch64 Assembly Printer
 ; CHECK-NEXT:       Free MachineFunction
 ; CHECK-NEXT: Pass Arguments:  -domtree

llvm/test/CodeGen/AArch64/arm64-opt-remarks-lazy-bfi.ll

@@ -36,9 +36,7 @@
 ; HOTNESS-NOT: Executing Pass
 ; HOTNESS: block-frequency: empty_func
 ; HOTNESS-NOT: Executing Pass
-; HOTNESS: Executing Pass 'MachineDominator Tree Construction'
-; HOTNESS-NEXT: Executing Pass 'Machine Natural Loop Construction'
-; HOTNESS-NEXT: Executing Pass 'AArch64 Assembly Printer'
+; HOTNESS: Executing Pass 'AArch64 Assembly Printer'
 
 ; HOTNESS: arm64-summary-remarks.ll:5:0: 1 instructions in function (hotness: 33)
 
@@ -47,8 +45,6 @@
 ; NO_HOTNESS-NEXT:  Freeing Pass 'Implement the 'patchable-function' attribute'
 ; NO_HOTNESS-NEXT: Executing Pass 'Lazy Machine Block Frequency Analysis'
 ; NO_HOTNESS-NEXT: Executing Pass 'Machine Optimization Remark Emitter'
-; NO_HOTNESS-NEXT: Executing Pass 'MachineDominator Tree Construction'
-; NO_HOTNESS-NEXT: Executing Pass 'Machine Natural Loop Construction'
 ; NO_HOTNESS-NEXT: Executing Pass 'AArch64 Assembly Printer'
 
 ; NO_HOTNESS: arm64-summary-remarks.ll:5:0: 1 instructions in function{{$}}

llvm/test/CodeGen/X86/O0-pipeline.ll

@@ -61,8 +61,6 @@
 ; CHECK-NEXT:       X86 Retpoline Thunks
 ; CHECK-NEXT:       Lazy Machine Block Frequency Analysis
 ; CHECK-NEXT:       Machine Optimization Remark Emitter
-; CHECK-NEXT:       MachineDominator Tree Construction
-; CHECK-NEXT:       Machine Natural Loop Construction
 ; CHECK-NEXT:       X86 Assembly Printer
 ; CHECK-NEXT:       Free MachineFunction
 

llvm/test/CodeGen/X86/O3-pipeline.ll

@@ -160,8 +160,6 @@
 ; CHECK-NEXT:       X86 Retpoline Thunks
 ; CHECK-NEXT:       Lazy Machine Block Frequency Analysis
 ; CHECK-NEXT:       Machine Optimization Remark Emitter
-; CHECK-NEXT:       MachineDominator Tree Construction
-; CHECK-NEXT:       Machine Natural Loop Construction
 ; CHECK-NEXT:       X86 Assembly Printer
 ; CHECK-NEXT:       Free MachineFunction