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115 lines
3.3 KiB
C++
115 lines
3.3 KiB
C++
//===--- LivePhysRegs.cpp - Live Physical Register Set --------------------===//
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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 the LivePhysRegs utility for tracking liveness of
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// physical registers across machine instructions in forward or backward order.
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// A more detailed description can be found in the corresponding header file.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/LivePhysRegs.h"
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#include "llvm/CodeGen/MachineInstrBundle.h"
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#include "llvm/Support/Debug.h"
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using namespace llvm;
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/// \brief Remove all registers from the set that get clobbered by the register
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/// mask.
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void LivePhysRegs::removeRegsInMask(const MachineOperand &MO) {
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SparseSet<unsigned>::iterator LRI = LiveRegs.begin();
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while (LRI != LiveRegs.end()) {
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if (MO.clobbersPhysReg(*LRI))
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LRI = LiveRegs.erase(LRI);
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else
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++LRI;
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}
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}
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/// Simulates liveness when stepping backwards over an instruction(bundle):
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/// Remove Defs, add uses. This is the recommended way of calculating liveness.
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void LivePhysRegs::stepBackward(const MachineInstr &MI) {
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// Remove defined registers and regmask kills from the set.
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for (ConstMIBundleOperands O(&MI); O.isValid(); ++O) {
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if (O->isReg()) {
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if (!O->isDef())
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continue;
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unsigned Reg = O->getReg();
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if (Reg == 0)
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continue;
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removeReg(Reg);
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} else if (O->isRegMask())
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removeRegsInMask(*O);
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}
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// Add uses to the set.
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for (ConstMIBundleOperands O(&MI); O.isValid(); ++O) {
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if (!O->isReg() || !O->readsReg() || O->isUndef())
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continue;
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unsigned Reg = O->getReg();
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if (Reg == 0)
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continue;
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addReg(Reg);
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}
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}
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/// Simulates liveness when stepping forward over an instruction(bundle): Remove
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/// killed-uses, add defs. This is the not recommended way, because it depends
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/// on accurate kill flags. If possible use stepBackwards() instead of this
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/// function.
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void LivePhysRegs::stepForward(const MachineInstr &MI) {
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SmallVector<unsigned, 4> Defs;
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// Remove killed registers from the set.
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for (ConstMIBundleOperands O(&MI); O.isValid(); ++O) {
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if (O->isReg()) {
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unsigned Reg = O->getReg();
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if (Reg == 0)
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continue;
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if (O->isDef()) {
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if (!O->isDead())
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Defs.push_back(Reg);
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} else {
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if (!O->isKill())
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continue;
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assert(O->isUse());
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removeReg(Reg);
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}
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} else if (O->isRegMask())
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removeRegsInMask(*O);
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}
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// Add defs to the set.
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for (unsigned i = 0, e = Defs.size(); i != e; ++i)
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addReg(Defs[i]);
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}
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/// Prin the currently live registers to OS.
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void LivePhysRegs::print(raw_ostream &OS) const {
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OS << "Live Registers:";
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if (!TRI) {
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OS << " (uninitialized)\n";
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return;
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}
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if (empty()) {
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OS << " (empty)\n";
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return;
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}
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for (const_iterator I = begin(), E = end(); I != E; ++I)
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OS << " " << PrintReg(*I, TRI);
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OS << "\n";
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}
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/// Dumps the currently live registers to the debug output.
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void LivePhysRegs::dump() const {
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#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
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dbgs() << " " << *this;
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#endif
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}
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