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Windows EH funclets need to be contiguous. The FuncletLayout pass will ensure that the funclets are together and begin with a funclet entry MBB. Differential Revision: http://reviews.llvm.org/D12943 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@247937 91177308-0d34-0410-b5e6-96231b3b80d8
98 lines
3.0 KiB
C++
98 lines
3.0 KiB
C++
//===-- FuncletLayout.cpp - Contiguously lay out funclets -----------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements basic block placement transformations which result in
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// funclets being contiguous.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/ADT/MapVector.h"
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#include "llvm/CodeGen/MachineBasicBlock.h"
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#include "llvm/CodeGen/MachineFunction.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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#include "llvm/CodeGen/MachineModuleInfo.h"
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using namespace llvm;
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#define DEBUG_TYPE "funclet-layout"
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namespace {
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class FuncletLayout : public MachineFunctionPass {
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public:
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static char ID; // Pass identification, replacement for typeid
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FuncletLayout() : MachineFunctionPass(ID) {
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initializeFuncletLayoutPass(*PassRegistry::getPassRegistry());
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}
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bool runOnMachineFunction(MachineFunction &F) override;
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};
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}
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static void
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collectFuncletMembers(MapVector<MachineBasicBlock *, int> &FuncletMembership,
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int Funclet, MachineBasicBlock *MBB) {
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// Don't revisit blocks.
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if (FuncletMembership.count(MBB) > 0)
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return;
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// Add this MBB to our funclet.
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FuncletMembership[MBB] = Funclet;
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bool IsReturn = false;
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int NumTerminators = 0;
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for (MachineInstr &MI : MBB->terminators()) {
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IsReturn |= MI.isReturn();
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++NumTerminators;
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}
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assert((!IsReturn || NumTerminators == 1) &&
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"Expected only one terminator when a return is present!");
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// Returns are boundaries where funclet transfer can occur, don't follow
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// successors.
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if (IsReturn)
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return;
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for (MachineBasicBlock *SMBB : MBB->successors())
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if (!SMBB->isEHPad())
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collectFuncletMembers(FuncletMembership, Funclet, SMBB);
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}
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char FuncletLayout::ID = 0;
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char &llvm::FuncletLayoutID = FuncletLayout::ID;
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INITIALIZE_PASS(FuncletLayout, "funclet-layout",
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"Contiguously Lay Out Funclets", false, false)
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bool FuncletLayout::runOnMachineFunction(MachineFunction &F) {
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// We don't have anything to do if there aren't any EH pads.
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if (!F.getMMI().hasEHFunclets())
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return false;
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SmallVector<MachineBasicBlock *, 16> FuncletBlocks;
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for (MachineBasicBlock &MBB : F)
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if (MBB.isEHFuncletEntry())
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FuncletBlocks.push_back(&MBB);
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// We don't have anything to do if there aren't any EH pads.
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if (FuncletBlocks.empty())
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return false;
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MapVector<MachineBasicBlock *, int> FuncletMembership;
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for (MachineBasicBlock *MBB : FuncletBlocks)
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collectFuncletMembers(FuncletMembership, MBB->getNumber(), MBB);
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for (std::pair<llvm::MachineBasicBlock *, int> &FuncletMember :
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FuncletMembership) {
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// Move this block to the end of the function.
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MachineBasicBlock *MBB = FuncletMember.first;
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MBB->moveAfter(--F.end());
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}
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// Conservatively assume we changed something.
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return true;
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}
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