Don't call destructors on MachineInstr and MachineOperand.

The series of patches leading up to this one makes llc -O0 run 8% faster.

When deallocating a MachineFunction, there is no need to visit all
MachineInstr and MachineOperand objects to deallocate them. All their
memory come from a BumpPtrAllocator that is about to be purged, and they
have empty destructors anyway.

This only applies when deallocating the MachineFunction.
DeleteMachineInstr() should still be used to recycle MI memory during
the codegen passes.

Remove the LeakDetector support for MachineInstr. I've never seen it
used before, and now it definitely doesn't work. With this patch, leaked
MachineInstrs would be much less of a problem since all of their memory
will be reclaimed by ~MachineFunction().

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171599 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/MachineInstr.h

@@ -43,6 +43,10 @@ class MachineMemOperand;
 //===----------------------------------------------------------------------===//
 /// MachineInstr - Representation of each machine instruction.
 ///
+/// This class isn't a POD type, but it must have a trivial destructor. When a
+/// MachineFunction is deleted, all the contained MachineInstrs are deallocated
+/// without having their destructor called.
+///
 class MachineInstr : public ilist_node<MachineInstr> {
 public:
   typedef MachineMemOperand **mmo_iterator;
@@ -90,6 +94,8 @@ private:
 
   MachineInstr(const MachineInstr&) LLVM_DELETED_FUNCTION;
   void operator=(const MachineInstr&) LLVM_DELETED_FUNCTION;
+  // Use MachineFunction::DeleteMachineInstr() instead.
+  ~MachineInstr() LLVM_DELETED_FUNCTION;
 
   // Intrusive list support
   friend struct ilist_traits<MachineInstr>;
@@ -106,8 +112,6 @@ private:
   MachineInstr(MachineFunction&, const MCInstrDesc &MCID,
                const DebugLoc dl, bool NoImp = false);
 
-  ~MachineInstr();
-
   // MachineInstrs are pool-allocated and owned by MachineFunction.
   friend class MachineFunction;
 

lib/CodeGen/MachineFunction.cpp

@@ -76,7 +76,13 @@ MachineFunction::MachineFunction(const Function *F, const TargetMachine &TM,
 }
 
 MachineFunction::~MachineFunction() {
-  BasicBlocks.clear();
+  // Don't call destructors on MachineInstr and MachineOperand. All of their
+  // memory comes from the BumpPtrAllocator which is about to be purged.
+  //
+  // Do call MachineBasicBlock destructors, it contains std::vectors.
+  for (iterator I = begin(), E = end(); I != E; I = BasicBlocks.erase(I))
+    I->Insts.clearAndLeakNodesUnsafely();
+
   InstructionRecycler.clear(Allocator);
   OperandRecycler.clear(Allocator);
   BasicBlockRecycler.clear(Allocator);
@@ -176,15 +182,17 @@ MachineFunction::CloneMachineInstr(const MachineInstr *Orig) {
 
 /// DeleteMachineInstr - Delete the given MachineInstr.
 ///
+/// This function also serves as the MachineInstr destructor - the real
+/// ~MachineInstr() destructor must be empty.
 void
 MachineFunction::DeleteMachineInstr(MachineInstr *MI) {
   // Strip it for parts. The operand array and the MI object itself are
   // independently recyclable.
   if (MI->Operands)
     deallocateOperandArray(MI->CapOperands, MI->Operands);
-  MI->Operands = 0;
-  MI->NumOperands = 0;
-  MI->~MachineInstr();
+  // Don't call ~MachineInstr() which must be trivial anyway because
+  // ~MachineFunction drops whole lists of MachineInstrs wihout calling their
+  // destructors.
   InstructionRecycler.Deallocate(Allocator, MI);
 }
 

lib/CodeGen/MachineInstr.cpp

@@ -35,7 +35,6 @@
 #include "llvm/MC/MCSymbol.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
-#include "llvm/Support/LeakDetector.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetInstrInfo.h"
@@ -544,8 +543,6 @@ MachineInstr::MachineInstr(MachineFunction &MF, const MCInstrDesc &tid,
 
   if (!NoImp)
     addImplicitDefUseOperands(MF);
-  // Make sure that we get added to a machine basicblock
-  LeakDetector::addGarbageObject(this);
 }
 
 /// MachineInstr ctor - Copies MachineInstr arg exactly
@@ -558,28 +555,12 @@ MachineInstr::MachineInstr(MachineFunction &MF, const MachineInstr &MI)
   CapOperands = OperandCapacity::get(MI.getNumOperands());
   Operands = MF.allocateOperandArray(CapOperands);
 
-  // Add operands
+  // Copy operands.
   for (unsigned i = 0; i != MI.getNumOperands(); ++i)
     addOperand(MF, MI.getOperand(i));
 
   // Copy all the sensible flags.
   setFlags(MI.Flags);
-
-  // Set parent to null.
-  Parent = 0;
-
-  LeakDetector::addGarbageObject(this);
-}
-
-MachineInstr::~MachineInstr() {
-  LeakDetector::removeGarbageObject(this);
-#ifndef NDEBUG
-  for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
-    assert(Operands[i].ParentMI == this && "ParentMI mismatch!");
-    assert((!Operands[i].isReg() || !Operands[i].isOnRegUseList()) &&
-           "Reg operand def/use list corrupted");
-  }
-#endif
 }
 
 /// getRegInfo - If this instruction is embedded into a MachineFunction,

lib/CodeGen/MachineRegisterInfo.cpp

@@ -30,12 +30,6 @@ MachineRegisterInfo::MachineRegisterInfo(const TargetRegisterInfo &TRI)
 }
 
 MachineRegisterInfo::~MachineRegisterInfo() {
-#ifndef NDEBUG
-  clearVirtRegs();
-  for (unsigned i = 0, e = TRI->getNumRegs(); i != e; ++i)
-    assert(!PhysRegUseDefLists[i] &&
-           "PhysRegUseDefLists has entries after all instructions are deleted");
-#endif
   delete [] PhysRegUseDefLists;
 }