forked from OSchip/llvm-project
1113 lines
34 KiB
C++
1113 lines
34 KiB
C++
//===- BitTracker.cpp -----------------------------------------------------===//
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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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// SSA-based bit propagation.
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//
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// The purpose of this code is, for a given virtual register, to provide
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// information about the value of each bit in the register. The values
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// of bits are represented by the class BitValue, and take one of four
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// cases: 0, 1, "ref" and "bottom". The 0 and 1 are rather clear, the
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// "ref" value means that the bit is a copy of another bit (which itself
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// cannot be a copy of yet another bit---such chains are not allowed).
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// A "ref" value is associated with a BitRef structure, which indicates
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// which virtual register, and which bit in that register is the origin
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// of the value. For example, given an instruction
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// vreg2 = ASL vreg1, 1
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// assuming that nothing is known about bits of vreg1, bit 1 of vreg2
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// will be a "ref" to (vreg1, 0). If there is a subsequent instruction
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// vreg3 = ASL vreg2, 2
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// then bit 3 of vreg3 will be a "ref" to (vreg1, 0) as well.
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// The "bottom" case means that the bit's value cannot be determined,
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// and that this virtual register actually defines it. The "bottom" case
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// is discussed in detail in BitTracker.h. In fact, "bottom" is a "ref
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// to self", so for the vreg1 above, the bit 0 of it will be a "ref" to
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// (vreg1, 0), bit 1 will be a "ref" to (vreg1, 1), etc.
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//
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// The tracker implements the Wegman-Zadeck algorithm, originally developed
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// for SSA-based constant propagation. Each register is represented as
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// a sequence of bits, with the convention that bit 0 is the least signi-
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// ficant bit. Each bit is propagated individually. The class RegisterCell
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// implements the register's representation, and is also the subject of
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// the lattice operations in the tracker.
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//
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// The intended usage of the bit tracker is to create a target-specific
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// machine instruction evaluator, pass the evaluator to the BitTracker
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// object, and run the tracker. The tracker will then collect the bit
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// value information for a given machine function. After that, it can be
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// queried for the cells for each virtual register.
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// Sample code:
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// const TargetSpecificEvaluator TSE(TRI, MRI);
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// BitTracker BT(TSE, MF);
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// BT.run();
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// ...
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// unsigned Reg = interestingRegister();
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// RegisterCell RC = BT.get(Reg);
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// if (RC[3].is(1))
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// Reg0bit3 = 1;
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//
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// The code below is intended to be fully target-independent.
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#include "BitTracker.h"
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#include "llvm/ADT/APInt.h"
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#include "llvm/ADT/BitVector.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/MachineInstr.h"
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#include "llvm/CodeGen/MachineOperand.h"
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#include "llvm/CodeGen/MachineRegisterInfo.h"
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#include "llvm/IR/Constants.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Target/TargetRegisterInfo.h"
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#include <cassert>
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#include <cstdint>
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#include <iterator>
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using namespace llvm;
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using BT = BitTracker;
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namespace {
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// Local trickery to pretty print a register (without the whole "%vreg"
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// business).
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struct printv {
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printv(unsigned r) : R(r) {}
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unsigned R;
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};
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raw_ostream &operator<< (raw_ostream &OS, const printv &PV) {
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if (PV.R)
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OS << 'v' << TargetRegisterInfo::virtReg2Index(PV.R);
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else
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OS << 's';
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return OS;
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}
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} // end anonymous namespace
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namespace llvm {
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raw_ostream &operator<<(raw_ostream &OS, const BT::BitValue &BV) {
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switch (BV.Type) {
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case BT::BitValue::Top:
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OS << 'T';
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break;
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case BT::BitValue::Zero:
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OS << '0';
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break;
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case BT::BitValue::One:
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OS << '1';
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break;
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case BT::BitValue::Ref:
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OS << printv(BV.RefI.Reg) << '[' << BV.RefI.Pos << ']';
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break;
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}
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return OS;
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}
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raw_ostream &operator<<(raw_ostream &OS, const BT::RegisterCell &RC) {
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unsigned n = RC.Bits.size();
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OS << "{ w:" << n;
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// Instead of printing each bit value individually, try to group them
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// into logical segments, such as sequences of 0 or 1 bits or references
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// to consecutive bits (e.g. "bits 3-5 are same as bits 7-9 of reg xyz").
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// "Start" will be the index of the beginning of the most recent segment.
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unsigned Start = 0;
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bool SeqRef = false; // A sequence of refs to consecutive bits.
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bool ConstRef = false; // A sequence of refs to the same bit.
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for (unsigned i = 1, n = RC.Bits.size(); i < n; ++i) {
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const BT::BitValue &V = RC[i];
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const BT::BitValue &SV = RC[Start];
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bool IsRef = (V.Type == BT::BitValue::Ref);
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// If the current value is the same as Start, skip to the next one.
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if (!IsRef && V == SV)
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continue;
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if (IsRef && SV.Type == BT::BitValue::Ref && V.RefI.Reg == SV.RefI.Reg) {
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if (Start+1 == i) {
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SeqRef = (V.RefI.Pos == SV.RefI.Pos+1);
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ConstRef = (V.RefI.Pos == SV.RefI.Pos);
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}
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if (SeqRef && V.RefI.Pos == SV.RefI.Pos+(i-Start))
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continue;
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if (ConstRef && V.RefI.Pos == SV.RefI.Pos)
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continue;
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}
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// The current value is different. Print the previous one and reset
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// the Start.
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OS << " [" << Start;
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unsigned Count = i - Start;
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if (Count == 1) {
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OS << "]:" << SV;
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} else {
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OS << '-' << i-1 << "]:";
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if (SV.Type == BT::BitValue::Ref && SeqRef)
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OS << printv(SV.RefI.Reg) << '[' << SV.RefI.Pos << '-'
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<< SV.RefI.Pos+(Count-1) << ']';
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else
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OS << SV;
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}
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Start = i;
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SeqRef = ConstRef = false;
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}
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OS << " [" << Start;
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unsigned Count = n - Start;
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if (n-Start == 1) {
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OS << "]:" << RC[Start];
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} else {
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OS << '-' << n-1 << "]:";
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const BT::BitValue &SV = RC[Start];
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if (SV.Type == BT::BitValue::Ref && SeqRef)
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OS << printv(SV.RefI.Reg) << '[' << SV.RefI.Pos << '-'
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<< SV.RefI.Pos+(Count-1) << ']';
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else
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OS << SV;
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}
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OS << " }";
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return OS;
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}
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} // end namespace llvm
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void BitTracker::print_cells(raw_ostream &OS) const {
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for (CellMapType::iterator I = Map.begin(), E = Map.end(); I != E; ++I)
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dbgs() << PrintReg(I->first, &ME.TRI) << " -> " << I->second << "\n";
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}
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BitTracker::BitTracker(const MachineEvaluator &E, MachineFunction &F)
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: Trace(false), ME(E), MF(F), MRI(F.getRegInfo()), Map(*new CellMapType) {}
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BitTracker::~BitTracker() {
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delete ⤅
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}
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// If we were allowed to update a cell for a part of a register, the meet
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// operation would need to be parametrized by the register number and the
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// exact part of the register, so that the computer BitRefs correspond to
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// the actual bits of the "self" register.
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// While this cannot happen in the current implementation, I'm not sure
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// if this should be ruled out in the future.
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bool BT::RegisterCell::meet(const RegisterCell &RC, unsigned SelfR) {
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// An example when "meet" can be invoked with SelfR == 0 is a phi node
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// with a physical register as an operand.
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assert(SelfR == 0 || TargetRegisterInfo::isVirtualRegister(SelfR));
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bool Changed = false;
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for (uint16_t i = 0, n = Bits.size(); i < n; ++i) {
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const BitValue &RCV = RC[i];
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Changed |= Bits[i].meet(RCV, BitRef(SelfR, i));
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}
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return Changed;
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}
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// Insert the entire cell RC into the current cell at position given by M.
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BT::RegisterCell &BT::RegisterCell::insert(const BT::RegisterCell &RC,
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const BitMask &M) {
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uint16_t B = M.first(), E = M.last(), W = width();
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// Sanity: M must be a valid mask for *this.
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assert(B < W && E < W);
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// Sanity: the masked part of *this must have the same number of bits
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// as the source.
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assert(B > E || E-B+1 == RC.width()); // B <= E => E-B+1 = |RC|.
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assert(B <= E || E+(W-B)+1 == RC.width()); // E < B => E+(W-B)+1 = |RC|.
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if (B <= E) {
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for (uint16_t i = 0; i <= E-B; ++i)
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Bits[i+B] = RC[i];
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} else {
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for (uint16_t i = 0; i < W-B; ++i)
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Bits[i+B] = RC[i];
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for (uint16_t i = 0; i <= E; ++i)
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Bits[i] = RC[i+(W-B)];
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}
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return *this;
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}
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BT::RegisterCell BT::RegisterCell::extract(const BitMask &M) const {
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uint16_t B = M.first(), E = M.last(), W = width();
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assert(B < W && E < W);
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if (B <= E) {
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RegisterCell RC(E-B+1);
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for (uint16_t i = B; i <= E; ++i)
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RC.Bits[i-B] = Bits[i];
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return RC;
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}
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RegisterCell RC(E+(W-B)+1);
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for (uint16_t i = 0; i < W-B; ++i)
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RC.Bits[i] = Bits[i+B];
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for (uint16_t i = 0; i <= E; ++i)
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RC.Bits[i+(W-B)] = Bits[i];
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return RC;
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}
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BT::RegisterCell &BT::RegisterCell::rol(uint16_t Sh) {
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// Rotate left (i.e. towards increasing bit indices).
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// Swap the two parts: [0..W-Sh-1] [W-Sh..W-1]
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uint16_t W = width();
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Sh = Sh % W;
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if (Sh == 0)
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return *this;
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RegisterCell Tmp(W-Sh);
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// Tmp = [0..W-Sh-1].
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for (uint16_t i = 0; i < W-Sh; ++i)
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Tmp[i] = Bits[i];
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// Shift [W-Sh..W-1] to [0..Sh-1].
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for (uint16_t i = 0; i < Sh; ++i)
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Bits[i] = Bits[W-Sh+i];
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// Copy Tmp to [Sh..W-1].
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for (uint16_t i = 0; i < W-Sh; ++i)
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Bits[i+Sh] = Tmp.Bits[i];
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return *this;
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}
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BT::RegisterCell &BT::RegisterCell::fill(uint16_t B, uint16_t E,
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const BitValue &V) {
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assert(B <= E);
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while (B < E)
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Bits[B++] = V;
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return *this;
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}
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BT::RegisterCell &BT::RegisterCell::cat(const RegisterCell &RC) {
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// Append the cell given as the argument to the "this" cell.
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// Bit 0 of RC becomes bit W of the result, where W is this->width().
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uint16_t W = width(), WRC = RC.width();
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Bits.resize(W+WRC);
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for (uint16_t i = 0; i < WRC; ++i)
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Bits[i+W] = RC.Bits[i];
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return *this;
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}
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uint16_t BT::RegisterCell::ct(bool B) const {
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uint16_t W = width();
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uint16_t C = 0;
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BitValue V = B;
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while (C < W && Bits[C] == V)
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C++;
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return C;
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}
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uint16_t BT::RegisterCell::cl(bool B) const {
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uint16_t W = width();
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uint16_t C = 0;
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BitValue V = B;
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while (C < W && Bits[W-(C+1)] == V)
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C++;
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return C;
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}
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bool BT::RegisterCell::operator== (const RegisterCell &RC) const {
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uint16_t W = Bits.size();
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if (RC.Bits.size() != W)
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return false;
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for (uint16_t i = 0; i < W; ++i)
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if (Bits[i] != RC[i])
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return false;
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return true;
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}
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BT::RegisterCell &BT::RegisterCell::regify(unsigned R) {
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for (unsigned i = 0, n = width(); i < n; ++i) {
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const BitValue &V = Bits[i];
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if (V.Type == BitValue::Ref && V.RefI.Reg == 0)
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Bits[i].RefI = BitRef(R, i);
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}
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return *this;
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}
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uint16_t BT::MachineEvaluator::getRegBitWidth(const RegisterRef &RR) const {
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// The general problem is with finding a register class that corresponds
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// to a given reference reg:sub. There can be several such classes, and
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// since we only care about the register size, it does not matter which
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// such class we would find.
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// The easiest way to accomplish what we want is to
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// 1. find a physical register PhysR from the same class as RR.Reg,
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// 2. find a physical register PhysS that corresponds to PhysR:RR.Sub,
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// 3. find a register class that contains PhysS.
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if (TargetRegisterInfo::isVirtualRegister(RR.Reg)) {
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const auto &VC = composeWithSubRegIndex(*MRI.getRegClass(RR.Reg), RR.Sub);
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return TRI.getRegSizeInBits(VC);
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}
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assert(TargetRegisterInfo::isPhysicalRegister(RR.Reg));
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unsigned PhysR = (RR.Sub == 0) ? RR.Reg : TRI.getSubReg(RR.Reg, RR.Sub);
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return getPhysRegBitWidth(PhysR);
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}
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BT::RegisterCell BT::MachineEvaluator::getCell(const RegisterRef &RR,
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const CellMapType &M) const {
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uint16_t BW = getRegBitWidth(RR);
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// Physical registers are assumed to be present in the map with an unknown
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// value. Don't actually insert anything in the map, just return the cell.
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if (TargetRegisterInfo::isPhysicalRegister(RR.Reg))
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return RegisterCell::self(0, BW);
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assert(TargetRegisterInfo::isVirtualRegister(RR.Reg));
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// For virtual registers that belong to a class that is not tracked,
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// generate an "unknown" value as well.
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const TargetRegisterClass *C = MRI.getRegClass(RR.Reg);
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if (!track(C))
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return RegisterCell::self(0, BW);
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CellMapType::const_iterator F = M.find(RR.Reg);
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if (F != M.end()) {
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if (!RR.Sub)
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return F->second;
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BitMask M = mask(RR.Reg, RR.Sub);
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return F->second.extract(M);
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}
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// If not found, create a "top" entry, but do not insert it in the map.
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return RegisterCell::top(BW);
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}
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void BT::MachineEvaluator::putCell(const RegisterRef &RR, RegisterCell RC,
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CellMapType &M) const {
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// While updating the cell map can be done in a meaningful way for
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// a part of a register, it makes little sense to implement it as the
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// SSA representation would never contain such "partial definitions".
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if (!TargetRegisterInfo::isVirtualRegister(RR.Reg))
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return;
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assert(RR.Sub == 0 && "Unexpected sub-register in definition");
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// Eliminate all ref-to-reg-0 bit values: replace them with "self".
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M[RR.Reg] = RC.regify(RR.Reg);
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}
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// Check if the cell represents a compile-time integer value.
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bool BT::MachineEvaluator::isInt(const RegisterCell &A) const {
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uint16_t W = A.width();
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for (uint16_t i = 0; i < W; ++i)
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if (!A[i].is(0) && !A[i].is(1))
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return false;
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return true;
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}
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// Convert a cell to the integer value. The result must fit in uint64_t.
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uint64_t BT::MachineEvaluator::toInt(const RegisterCell &A) const {
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assert(isInt(A));
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uint64_t Val = 0;
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uint16_t W = A.width();
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for (uint16_t i = 0; i < W; ++i) {
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Val <<= 1;
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Val |= A[i].is(1);
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}
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return Val;
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}
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// Evaluator helper functions. These implement some common operation on
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// register cells that can be used to implement target-specific instructions
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// in a target-specific evaluator.
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BT::RegisterCell BT::MachineEvaluator::eIMM(int64_t V, uint16_t W) const {
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RegisterCell Res(W);
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// For bits beyond the 63rd, this will generate the sign bit of V.
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for (uint16_t i = 0; i < W; ++i) {
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Res[i] = BitValue(V & 1);
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V >>= 1;
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}
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return Res;
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}
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BT::RegisterCell BT::MachineEvaluator::eIMM(const ConstantInt *CI) const {
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const APInt &A = CI->getValue();
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uint16_t BW = A.getBitWidth();
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assert((unsigned)BW == A.getBitWidth() && "BitWidth overflow");
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RegisterCell Res(BW);
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for (uint16_t i = 0; i < BW; ++i)
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Res[i] = A[i];
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return Res;
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}
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BT::RegisterCell BT::MachineEvaluator::eADD(const RegisterCell &A1,
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const RegisterCell &A2) const {
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uint16_t W = A1.width();
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assert(W == A2.width());
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RegisterCell Res(W);
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bool Carry = false;
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uint16_t I;
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for (I = 0; I < W; ++I) {
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const BitValue &V1 = A1[I];
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const BitValue &V2 = A2[I];
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if (!V1.num() || !V2.num())
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break;
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unsigned S = bool(V1) + bool(V2) + Carry;
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Res[I] = BitValue(S & 1);
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Carry = (S > 1);
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}
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for (; I < W; ++I) {
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const BitValue &V1 = A1[I];
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const BitValue &V2 = A2[I];
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// If the next bit is same as Carry, the result will be 0 plus the
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// other bit. The Carry bit will remain unchanged.
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if (V1.is(Carry))
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Res[I] = BitValue::ref(V2);
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else if (V2.is(Carry))
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Res[I] = BitValue::ref(V1);
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else
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break;
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}
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for (; I < W; ++I)
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Res[I] = BitValue::self();
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return Res;
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}
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|
|
|
BT::RegisterCell BT::MachineEvaluator::eSUB(const RegisterCell &A1,
|
|
const RegisterCell &A2) const {
|
|
uint16_t W = A1.width();
|
|
assert(W == A2.width());
|
|
RegisterCell Res(W);
|
|
bool Borrow = false;
|
|
uint16_t I;
|
|
for (I = 0; I < W; ++I) {
|
|
const BitValue &V1 = A1[I];
|
|
const BitValue &V2 = A2[I];
|
|
if (!V1.num() || !V2.num())
|
|
break;
|
|
unsigned S = bool(V1) - bool(V2) - Borrow;
|
|
Res[I] = BitValue(S & 1);
|
|
Borrow = (S > 1);
|
|
}
|
|
for (; I < W; ++I) {
|
|
const BitValue &V1 = A1[I];
|
|
const BitValue &V2 = A2[I];
|
|
if (V1.is(Borrow)) {
|
|
Res[I] = BitValue::ref(V2);
|
|
break;
|
|
}
|
|
if (V2.is(Borrow))
|
|
Res[I] = BitValue::ref(V1);
|
|
else
|
|
break;
|
|
}
|
|
for (; I < W; ++I)
|
|
Res[I] = BitValue::self();
|
|
return Res;
|
|
}
|
|
|
|
BT::RegisterCell BT::MachineEvaluator::eMLS(const RegisterCell &A1,
|
|
const RegisterCell &A2) const {
|
|
uint16_t W = A1.width() + A2.width();
|
|
uint16_t Z = A1.ct(false) + A2.ct(false);
|
|
RegisterCell Res(W);
|
|
Res.fill(0, Z, BitValue::Zero);
|
|
Res.fill(Z, W, BitValue::self());
|
|
return Res;
|
|
}
|
|
|
|
BT::RegisterCell BT::MachineEvaluator::eMLU(const RegisterCell &A1,
|
|
const RegisterCell &A2) const {
|
|
uint16_t W = A1.width() + A2.width();
|
|
uint16_t Z = A1.ct(false) + A2.ct(false);
|
|
RegisterCell Res(W);
|
|
Res.fill(0, Z, BitValue::Zero);
|
|
Res.fill(Z, W, BitValue::self());
|
|
return Res;
|
|
}
|
|
|
|
BT::RegisterCell BT::MachineEvaluator::eASL(const RegisterCell &A1,
|
|
uint16_t Sh) const {
|
|
assert(Sh <= A1.width());
|
|
RegisterCell Res = RegisterCell::ref(A1);
|
|
Res.rol(Sh);
|
|
Res.fill(0, Sh, BitValue::Zero);
|
|
return Res;
|
|
}
|
|
|
|
BT::RegisterCell BT::MachineEvaluator::eLSR(const RegisterCell &A1,
|
|
uint16_t Sh) const {
|
|
uint16_t W = A1.width();
|
|
assert(Sh <= W);
|
|
RegisterCell Res = RegisterCell::ref(A1);
|
|
Res.rol(W-Sh);
|
|
Res.fill(W-Sh, W, BitValue::Zero);
|
|
return Res;
|
|
}
|
|
|
|
BT::RegisterCell BT::MachineEvaluator::eASR(const RegisterCell &A1,
|
|
uint16_t Sh) const {
|
|
uint16_t W = A1.width();
|
|
assert(Sh <= W);
|
|
RegisterCell Res = RegisterCell::ref(A1);
|
|
BitValue Sign = Res[W-1];
|
|
Res.rol(W-Sh);
|
|
Res.fill(W-Sh, W, Sign);
|
|
return Res;
|
|
}
|
|
|
|
BT::RegisterCell BT::MachineEvaluator::eAND(const RegisterCell &A1,
|
|
const RegisterCell &A2) const {
|
|
uint16_t W = A1.width();
|
|
assert(W == A2.width());
|
|
RegisterCell Res(W);
|
|
for (uint16_t i = 0; i < W; ++i) {
|
|
const BitValue &V1 = A1[i];
|
|
const BitValue &V2 = A2[i];
|
|
if (V1.is(1))
|
|
Res[i] = BitValue::ref(V2);
|
|
else if (V2.is(1))
|
|
Res[i] = BitValue::ref(V1);
|
|
else if (V1.is(0) || V2.is(0))
|
|
Res[i] = BitValue::Zero;
|
|
else if (V1 == V2)
|
|
Res[i] = V1;
|
|
else
|
|
Res[i] = BitValue::self();
|
|
}
|
|
return Res;
|
|
}
|
|
|
|
BT::RegisterCell BT::MachineEvaluator::eORL(const RegisterCell &A1,
|
|
const RegisterCell &A2) const {
|
|
uint16_t W = A1.width();
|
|
assert(W == A2.width());
|
|
RegisterCell Res(W);
|
|
for (uint16_t i = 0; i < W; ++i) {
|
|
const BitValue &V1 = A1[i];
|
|
const BitValue &V2 = A2[i];
|
|
if (V1.is(1) || V2.is(1))
|
|
Res[i] = BitValue::One;
|
|
else if (V1.is(0))
|
|
Res[i] = BitValue::ref(V2);
|
|
else if (V2.is(0))
|
|
Res[i] = BitValue::ref(V1);
|
|
else if (V1 == V2)
|
|
Res[i] = V1;
|
|
else
|
|
Res[i] = BitValue::self();
|
|
}
|
|
return Res;
|
|
}
|
|
|
|
BT::RegisterCell BT::MachineEvaluator::eXOR(const RegisterCell &A1,
|
|
const RegisterCell &A2) const {
|
|
uint16_t W = A1.width();
|
|
assert(W == A2.width());
|
|
RegisterCell Res(W);
|
|
for (uint16_t i = 0; i < W; ++i) {
|
|
const BitValue &V1 = A1[i];
|
|
const BitValue &V2 = A2[i];
|
|
if (V1.is(0))
|
|
Res[i] = BitValue::ref(V2);
|
|
else if (V2.is(0))
|
|
Res[i] = BitValue::ref(V1);
|
|
else if (V1 == V2)
|
|
Res[i] = BitValue::Zero;
|
|
else
|
|
Res[i] = BitValue::self();
|
|
}
|
|
return Res;
|
|
}
|
|
|
|
BT::RegisterCell BT::MachineEvaluator::eNOT(const RegisterCell &A1) const {
|
|
uint16_t W = A1.width();
|
|
RegisterCell Res(W);
|
|
for (uint16_t i = 0; i < W; ++i) {
|
|
const BitValue &V = A1[i];
|
|
if (V.is(0))
|
|
Res[i] = BitValue::One;
|
|
else if (V.is(1))
|
|
Res[i] = BitValue::Zero;
|
|
else
|
|
Res[i] = BitValue::self();
|
|
}
|
|
return Res;
|
|
}
|
|
|
|
BT::RegisterCell BT::MachineEvaluator::eSET(const RegisterCell &A1,
|
|
uint16_t BitN) const {
|
|
assert(BitN < A1.width());
|
|
RegisterCell Res = RegisterCell::ref(A1);
|
|
Res[BitN] = BitValue::One;
|
|
return Res;
|
|
}
|
|
|
|
BT::RegisterCell BT::MachineEvaluator::eCLR(const RegisterCell &A1,
|
|
uint16_t BitN) const {
|
|
assert(BitN < A1.width());
|
|
RegisterCell Res = RegisterCell::ref(A1);
|
|
Res[BitN] = BitValue::Zero;
|
|
return Res;
|
|
}
|
|
|
|
BT::RegisterCell BT::MachineEvaluator::eCLB(const RegisterCell &A1, bool B,
|
|
uint16_t W) const {
|
|
uint16_t C = A1.cl(B), AW = A1.width();
|
|
// If the last leading non-B bit is not a constant, then we don't know
|
|
// the real count.
|
|
if ((C < AW && A1[AW-1-C].num()) || C == AW)
|
|
return eIMM(C, W);
|
|
return RegisterCell::self(0, W);
|
|
}
|
|
|
|
BT::RegisterCell BT::MachineEvaluator::eCTB(const RegisterCell &A1, bool B,
|
|
uint16_t W) const {
|
|
uint16_t C = A1.ct(B), AW = A1.width();
|
|
// If the last trailing non-B bit is not a constant, then we don't know
|
|
// the real count.
|
|
if ((C < AW && A1[C].num()) || C == AW)
|
|
return eIMM(C, W);
|
|
return RegisterCell::self(0, W);
|
|
}
|
|
|
|
BT::RegisterCell BT::MachineEvaluator::eSXT(const RegisterCell &A1,
|
|
uint16_t FromN) const {
|
|
uint16_t W = A1.width();
|
|
assert(FromN <= W);
|
|
RegisterCell Res = RegisterCell::ref(A1);
|
|
BitValue Sign = Res[FromN-1];
|
|
// Sign-extend "inreg".
|
|
Res.fill(FromN, W, Sign);
|
|
return Res;
|
|
}
|
|
|
|
BT::RegisterCell BT::MachineEvaluator::eZXT(const RegisterCell &A1,
|
|
uint16_t FromN) const {
|
|
uint16_t W = A1.width();
|
|
assert(FromN <= W);
|
|
RegisterCell Res = RegisterCell::ref(A1);
|
|
Res.fill(FromN, W, BitValue::Zero);
|
|
return Res;
|
|
}
|
|
|
|
BT::RegisterCell BT::MachineEvaluator::eXTR(const RegisterCell &A1,
|
|
uint16_t B, uint16_t E) const {
|
|
uint16_t W = A1.width();
|
|
assert(B < W && E <= W);
|
|
if (B == E)
|
|
return RegisterCell(0);
|
|
uint16_t Last = (E > 0) ? E-1 : W-1;
|
|
RegisterCell Res = RegisterCell::ref(A1).extract(BT::BitMask(B, Last));
|
|
// Return shorter cell.
|
|
return Res;
|
|
}
|
|
|
|
BT::RegisterCell BT::MachineEvaluator::eINS(const RegisterCell &A1,
|
|
const RegisterCell &A2, uint16_t AtN) const {
|
|
uint16_t W1 = A1.width(), W2 = A2.width();
|
|
(void)W1;
|
|
assert(AtN < W1 && AtN+W2 <= W1);
|
|
// Copy bits from A1, insert A2 at position AtN.
|
|
RegisterCell Res = RegisterCell::ref(A1);
|
|
if (W2 > 0)
|
|
Res.insert(RegisterCell::ref(A2), BT::BitMask(AtN, AtN+W2-1));
|
|
return Res;
|
|
}
|
|
|
|
BT::BitMask BT::MachineEvaluator::mask(unsigned Reg, unsigned Sub) const {
|
|
assert(Sub == 0 && "Generic BitTracker::mask called for Sub != 0");
|
|
uint16_t W = getRegBitWidth(Reg);
|
|
assert(W > 0 && "Cannot generate mask for empty register");
|
|
return BitMask(0, W-1);
|
|
}
|
|
|
|
uint16_t BT::MachineEvaluator::getPhysRegBitWidth(unsigned Reg) const {
|
|
assert(TargetRegisterInfo::isPhysicalRegister(Reg));
|
|
const TargetRegisterClass &PC = *TRI.getMinimalPhysRegClass(Reg);
|
|
return TRI.getRegSizeInBits(PC);
|
|
}
|
|
|
|
bool BT::MachineEvaluator::evaluate(const MachineInstr &MI,
|
|
const CellMapType &Inputs,
|
|
CellMapType &Outputs) const {
|
|
unsigned Opc = MI.getOpcode();
|
|
switch (Opc) {
|
|
case TargetOpcode::REG_SEQUENCE: {
|
|
RegisterRef RD = MI.getOperand(0);
|
|
assert(RD.Sub == 0);
|
|
RegisterRef RS = MI.getOperand(1);
|
|
unsigned SS = MI.getOperand(2).getImm();
|
|
RegisterRef RT = MI.getOperand(3);
|
|
unsigned ST = MI.getOperand(4).getImm();
|
|
assert(SS != ST);
|
|
|
|
uint16_t W = getRegBitWidth(RD);
|
|
RegisterCell Res(W);
|
|
Res.insert(RegisterCell::ref(getCell(RS, Inputs)), mask(RD.Reg, SS));
|
|
Res.insert(RegisterCell::ref(getCell(RT, Inputs)), mask(RD.Reg, ST));
|
|
putCell(RD, Res, Outputs);
|
|
break;
|
|
}
|
|
|
|
case TargetOpcode::COPY: {
|
|
// COPY can transfer a smaller register into a wider one.
|
|
// If that is the case, fill the remaining high bits with 0.
|
|
RegisterRef RD = MI.getOperand(0);
|
|
RegisterRef RS = MI.getOperand(1);
|
|
assert(RD.Sub == 0);
|
|
uint16_t WD = getRegBitWidth(RD);
|
|
uint16_t WS = getRegBitWidth(RS);
|
|
assert(WD >= WS);
|
|
RegisterCell Src = getCell(RS, Inputs);
|
|
RegisterCell Res(WD);
|
|
Res.insert(Src, BitMask(0, WS-1));
|
|
Res.fill(WS, WD, BitValue::Zero);
|
|
putCell(RD, Res, Outputs);
|
|
break;
|
|
}
|
|
|
|
default:
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
// Main W-Z implementation.
|
|
|
|
void BT::visitPHI(const MachineInstr &PI) {
|
|
int ThisN = PI.getParent()->getNumber();
|
|
if (Trace)
|
|
dbgs() << "Visit FI(BB#" << ThisN << "): " << PI;
|
|
|
|
const MachineOperand &MD = PI.getOperand(0);
|
|
assert(MD.getSubReg() == 0 && "Unexpected sub-register in definition");
|
|
RegisterRef DefRR(MD);
|
|
uint16_t DefBW = ME.getRegBitWidth(DefRR);
|
|
|
|
RegisterCell DefC = ME.getCell(DefRR, Map);
|
|
if (DefC == RegisterCell::self(DefRR.Reg, DefBW)) // XXX slow
|
|
return;
|
|
|
|
bool Changed = false;
|
|
|
|
for (unsigned i = 1, n = PI.getNumOperands(); i < n; i += 2) {
|
|
const MachineBasicBlock *PB = PI.getOperand(i + 1).getMBB();
|
|
int PredN = PB->getNumber();
|
|
if (Trace)
|
|
dbgs() << " edge BB#" << PredN << "->BB#" << ThisN;
|
|
if (!EdgeExec.count(CFGEdge(PredN, ThisN))) {
|
|
if (Trace)
|
|
dbgs() << " not executable\n";
|
|
continue;
|
|
}
|
|
|
|
RegisterRef RU = PI.getOperand(i);
|
|
RegisterCell ResC = ME.getCell(RU, Map);
|
|
if (Trace)
|
|
dbgs() << " input reg: " << PrintReg(RU.Reg, &ME.TRI, RU.Sub)
|
|
<< " cell: " << ResC << "\n";
|
|
Changed |= DefC.meet(ResC, DefRR.Reg);
|
|
}
|
|
|
|
if (Changed) {
|
|
if (Trace)
|
|
dbgs() << "Output: " << PrintReg(DefRR.Reg, &ME.TRI, DefRR.Sub)
|
|
<< " cell: " << DefC << "\n";
|
|
ME.putCell(DefRR, DefC, Map);
|
|
visitUsesOf(DefRR.Reg);
|
|
}
|
|
}
|
|
|
|
void BT::visitNonBranch(const MachineInstr &MI) {
|
|
if (Trace) {
|
|
int ThisN = MI.getParent()->getNumber();
|
|
dbgs() << "Visit MI(BB#" << ThisN << "): " << MI;
|
|
}
|
|
if (MI.isDebugValue())
|
|
return;
|
|
assert(!MI.isBranch() && "Unexpected branch instruction");
|
|
|
|
CellMapType ResMap;
|
|
bool Eval = ME.evaluate(MI, Map, ResMap);
|
|
|
|
if (Trace && Eval) {
|
|
for (unsigned i = 0, n = MI.getNumOperands(); i < n; ++i) {
|
|
const MachineOperand &MO = MI.getOperand(i);
|
|
if (!MO.isReg() || !MO.isUse())
|
|
continue;
|
|
RegisterRef RU(MO);
|
|
dbgs() << " input reg: " << PrintReg(RU.Reg, &ME.TRI, RU.Sub)
|
|
<< " cell: " << ME.getCell(RU, Map) << "\n";
|
|
}
|
|
dbgs() << "Outputs:\n";
|
|
for (CellMapType::iterator I = ResMap.begin(), E = ResMap.end();
|
|
I != E; ++I) {
|
|
RegisterRef RD(I->first);
|
|
dbgs() << " " << PrintReg(I->first, &ME.TRI) << " cell: "
|
|
<< ME.getCell(RD, ResMap) << "\n";
|
|
}
|
|
}
|
|
|
|
// Iterate over all definitions of the instruction, and update the
|
|
// cells accordingly.
|
|
for (unsigned i = 0, n = MI.getNumOperands(); i < n; ++i) {
|
|
const MachineOperand &MO = MI.getOperand(i);
|
|
// Visit register defs only.
|
|
if (!MO.isReg() || !MO.isDef())
|
|
continue;
|
|
RegisterRef RD(MO);
|
|
assert(RD.Sub == 0 && "Unexpected sub-register in definition");
|
|
if (!TargetRegisterInfo::isVirtualRegister(RD.Reg))
|
|
continue;
|
|
|
|
bool Changed = false;
|
|
if (!Eval || ResMap.count(RD.Reg) == 0) {
|
|
// Set to "ref" (aka "bottom").
|
|
uint16_t DefBW = ME.getRegBitWidth(RD);
|
|
RegisterCell RefC = RegisterCell::self(RD.Reg, DefBW);
|
|
if (RefC != ME.getCell(RD, Map)) {
|
|
ME.putCell(RD, RefC, Map);
|
|
Changed = true;
|
|
}
|
|
} else {
|
|
RegisterCell DefC = ME.getCell(RD, Map);
|
|
RegisterCell ResC = ME.getCell(RD, ResMap);
|
|
// This is a non-phi instruction, so the values of the inputs come
|
|
// from the same registers each time this instruction is evaluated.
|
|
// During the propagation, the values of the inputs can become lowered
|
|
// in the sense of the lattice operation, which may cause different
|
|
// results to be calculated in subsequent evaluations. This should
|
|
// not cause the bottoming of the result in the map, since the new
|
|
// result is already reflecting the lowered inputs.
|
|
for (uint16_t i = 0, w = DefC.width(); i < w; ++i) {
|
|
BitValue &V = DefC[i];
|
|
// Bits that are already "bottom" should not be updated.
|
|
if (V.Type == BitValue::Ref && V.RefI.Reg == RD.Reg)
|
|
continue;
|
|
// Same for those that are identical in DefC and ResC.
|
|
if (V == ResC[i])
|
|
continue;
|
|
V = ResC[i];
|
|
Changed = true;
|
|
}
|
|
if (Changed)
|
|
ME.putCell(RD, DefC, Map);
|
|
}
|
|
if (Changed)
|
|
visitUsesOf(RD.Reg);
|
|
}
|
|
}
|
|
|
|
void BT::visitBranchesFrom(const MachineInstr &BI) {
|
|
const MachineBasicBlock &B = *BI.getParent();
|
|
MachineBasicBlock::const_iterator It = BI, End = B.end();
|
|
BranchTargetList Targets, BTs;
|
|
bool FallsThrough = true, DefaultToAll = false;
|
|
int ThisN = B.getNumber();
|
|
|
|
do {
|
|
BTs.clear();
|
|
const MachineInstr &MI = *It;
|
|
if (Trace)
|
|
dbgs() << "Visit BR(BB#" << ThisN << "): " << MI;
|
|
assert(MI.isBranch() && "Expecting branch instruction");
|
|
InstrExec.insert(&MI);
|
|
bool Eval = ME.evaluate(MI, Map, BTs, FallsThrough);
|
|
if (!Eval) {
|
|
// If the evaluation failed, we will add all targets. Keep going in
|
|
// the loop to mark all executable branches as such.
|
|
DefaultToAll = true;
|
|
FallsThrough = true;
|
|
if (Trace)
|
|
dbgs() << " failed to evaluate: will add all CFG successors\n";
|
|
} else if (!DefaultToAll) {
|
|
// If evaluated successfully add the targets to the cumulative list.
|
|
if (Trace) {
|
|
dbgs() << " adding targets:";
|
|
for (unsigned i = 0, n = BTs.size(); i < n; ++i)
|
|
dbgs() << " BB#" << BTs[i]->getNumber();
|
|
if (FallsThrough)
|
|
dbgs() << "\n falls through\n";
|
|
else
|
|
dbgs() << "\n does not fall through\n";
|
|
}
|
|
Targets.insert(BTs.begin(), BTs.end());
|
|
}
|
|
++It;
|
|
} while (FallsThrough && It != End);
|
|
|
|
using succ_iterator = MachineBasicBlock::const_succ_iterator;
|
|
|
|
if (!DefaultToAll) {
|
|
// Need to add all CFG successors that lead to EH landing pads.
|
|
// There won't be explicit branches to these blocks, but they must
|
|
// be processed.
|
|
for (succ_iterator I = B.succ_begin(), E = B.succ_end(); I != E; ++I) {
|
|
const MachineBasicBlock *SB = *I;
|
|
if (SB->isEHPad())
|
|
Targets.insert(SB);
|
|
}
|
|
if (FallsThrough) {
|
|
MachineFunction::const_iterator BIt = B.getIterator();
|
|
MachineFunction::const_iterator Next = std::next(BIt);
|
|
if (Next != MF.end())
|
|
Targets.insert(&*Next);
|
|
}
|
|
} else {
|
|
for (succ_iterator I = B.succ_begin(), E = B.succ_end(); I != E; ++I)
|
|
Targets.insert(*I);
|
|
}
|
|
|
|
for (unsigned i = 0, n = Targets.size(); i < n; ++i) {
|
|
int TargetN = Targets[i]->getNumber();
|
|
FlowQ.push(CFGEdge(ThisN, TargetN));
|
|
}
|
|
}
|
|
|
|
void BT::visitUsesOf(unsigned Reg) {
|
|
if (Trace)
|
|
dbgs() << "visiting uses of " << PrintReg(Reg, &ME.TRI) << "\n";
|
|
|
|
using use_iterator = MachineRegisterInfo::use_nodbg_iterator;
|
|
|
|
use_iterator End = MRI.use_nodbg_end();
|
|
for (use_iterator I = MRI.use_nodbg_begin(Reg); I != End; ++I) {
|
|
MachineInstr *UseI = I->getParent();
|
|
if (!InstrExec.count(UseI))
|
|
continue;
|
|
if (UseI->isPHI())
|
|
visitPHI(*UseI);
|
|
else if (!UseI->isBranch())
|
|
visitNonBranch(*UseI);
|
|
else
|
|
visitBranchesFrom(*UseI);
|
|
}
|
|
}
|
|
|
|
BT::RegisterCell BT::get(RegisterRef RR) const {
|
|
return ME.getCell(RR, Map);
|
|
}
|
|
|
|
void BT::put(RegisterRef RR, const RegisterCell &RC) {
|
|
ME.putCell(RR, RC, Map);
|
|
}
|
|
|
|
// Replace all references to bits from OldRR with the corresponding bits
|
|
// in NewRR.
|
|
void BT::subst(RegisterRef OldRR, RegisterRef NewRR) {
|
|
assert(Map.count(OldRR.Reg) > 0 && "OldRR not present in map");
|
|
BitMask OM = ME.mask(OldRR.Reg, OldRR.Sub);
|
|
BitMask NM = ME.mask(NewRR.Reg, NewRR.Sub);
|
|
uint16_t OMB = OM.first(), OME = OM.last();
|
|
uint16_t NMB = NM.first(), NME = NM.last();
|
|
(void)NME;
|
|
assert((OME-OMB == NME-NMB) &&
|
|
"Substituting registers of different lengths");
|
|
for (CellMapType::iterator I = Map.begin(), E = Map.end(); I != E; ++I) {
|
|
RegisterCell &RC = I->second;
|
|
for (uint16_t i = 0, w = RC.width(); i < w; ++i) {
|
|
BitValue &V = RC[i];
|
|
if (V.Type != BitValue::Ref || V.RefI.Reg != OldRR.Reg)
|
|
continue;
|
|
if (V.RefI.Pos < OMB || V.RefI.Pos > OME)
|
|
continue;
|
|
V.RefI.Reg = NewRR.Reg;
|
|
V.RefI.Pos += NMB-OMB;
|
|
}
|
|
}
|
|
}
|
|
|
|
// Check if the block has been "executed" during propagation. (If not, the
|
|
// block is dead, but it may still appear to be reachable.)
|
|
bool BT::reached(const MachineBasicBlock *B) const {
|
|
int BN = B->getNumber();
|
|
assert(BN >= 0);
|
|
return ReachedBB.count(BN);
|
|
}
|
|
|
|
// Visit an individual instruction. This could be a newly added instruction,
|
|
// or one that has been modified by an optimization.
|
|
void BT::visit(const MachineInstr &MI) {
|
|
assert(!MI.isBranch() && "Only non-branches are allowed");
|
|
InstrExec.insert(&MI);
|
|
visitNonBranch(MI);
|
|
// The call to visitNonBranch could propagate the changes until a branch
|
|
// is actually visited. This could result in adding CFG edges to the flow
|
|
// queue. Since the queue won't be processed, clear it.
|
|
while (!FlowQ.empty())
|
|
FlowQ.pop();
|
|
}
|
|
|
|
void BT::reset() {
|
|
EdgeExec.clear();
|
|
InstrExec.clear();
|
|
Map.clear();
|
|
ReachedBB.clear();
|
|
ReachedBB.reserve(MF.size());
|
|
}
|
|
|
|
void BT::run() {
|
|
reset();
|
|
assert(FlowQ.empty());
|
|
|
|
using MachineFlowGraphTraits = GraphTraits<const MachineFunction*>;
|
|
|
|
const MachineBasicBlock *Entry = MachineFlowGraphTraits::getEntryNode(&MF);
|
|
|
|
unsigned MaxBN = 0;
|
|
for (MachineFunction::const_iterator I = MF.begin(), E = MF.end();
|
|
I != E; ++I) {
|
|
assert(I->getNumber() >= 0 && "Disconnected block");
|
|
unsigned BN = I->getNumber();
|
|
if (BN > MaxBN)
|
|
MaxBN = BN;
|
|
}
|
|
|
|
// Keep track of visited blocks.
|
|
BitVector BlockScanned(MaxBN+1);
|
|
|
|
int EntryN = Entry->getNumber();
|
|
// Generate a fake edge to get something to start with.
|
|
FlowQ.push(CFGEdge(-1, EntryN));
|
|
|
|
while (!FlowQ.empty()) {
|
|
CFGEdge Edge = FlowQ.front();
|
|
FlowQ.pop();
|
|
|
|
if (EdgeExec.count(Edge))
|
|
continue;
|
|
EdgeExec.insert(Edge);
|
|
ReachedBB.insert(Edge.second);
|
|
|
|
const MachineBasicBlock &B = *MF.getBlockNumbered(Edge.second);
|
|
MachineBasicBlock::const_iterator It = B.begin(), End = B.end();
|
|
// Visit PHI nodes first.
|
|
while (It != End && It->isPHI()) {
|
|
const MachineInstr &PI = *It++;
|
|
InstrExec.insert(&PI);
|
|
visitPHI(PI);
|
|
}
|
|
|
|
// If this block has already been visited through a flow graph edge,
|
|
// then the instructions have already been processed. Any updates to
|
|
// the cells would now only happen through visitUsesOf...
|
|
if (BlockScanned[Edge.second])
|
|
continue;
|
|
BlockScanned[Edge.second] = true;
|
|
|
|
// Visit non-branch instructions.
|
|
while (It != End && !It->isBranch()) {
|
|
const MachineInstr &MI = *It++;
|
|
InstrExec.insert(&MI);
|
|
visitNonBranch(MI);
|
|
}
|
|
// If block end has been reached, add the fall-through edge to the queue.
|
|
if (It == End) {
|
|
MachineFunction::const_iterator BIt = B.getIterator();
|
|
MachineFunction::const_iterator Next = std::next(BIt);
|
|
if (Next != MF.end() && B.isSuccessor(&*Next)) {
|
|
int ThisN = B.getNumber();
|
|
int NextN = Next->getNumber();
|
|
FlowQ.push(CFGEdge(ThisN, NextN));
|
|
}
|
|
} else {
|
|
// Handle the remaining sequence of branches. This function will update
|
|
// the work queue.
|
|
visitBranchesFrom(*It);
|
|
}
|
|
} // while (!FlowQ->empty())
|
|
|
|
if (Trace)
|
|
print_cells(dbgs() << "Cells after propagation:\n");
|
|
}
|