llvm/llvm/lib/Target/WebAssembly/WebAssemblyRegColoring.cpp

//===-- WebAssemblyRegColoring.cpp - Register coloring --------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
///
/// \file
/// This file implements a virtual register coloring pass.
///
/// WebAssembly doesn't have a fixed number of registers, but it is still
/// desirable to minimize the total number of registers used in each function.
///
/// This code is modeled after lib/CodeGen/StackSlotColoring.cpp.
///
//===----------------------------------------------------------------------===//

#include "WebAssembly.h"
#include "WebAssemblyMachineFunctionInfo.h"
#include "llvm/CodeGen/LiveIntervals.h"
#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
usingnamespacellvm;

#define DEBUG_TYPE …

namespace {
class WebAssemblyRegColoring final : public MachineFunctionPass { … };
} // end anonymous namespace

char WebAssemblyRegColoring::ID = …;
INITIALIZE_PASS(…)

FunctionPass *llvm::createWebAssemblyRegColoring() { … }

// Compute the total spill weight for VReg.
static float computeWeight(const MachineRegisterInfo *MRI,
                           const MachineBlockFrequencyInfo *MBFI,
                           unsigned VReg) { … }

// Create a map of "Register -> vector of <SlotIndex, DBG_VALUE>".
// The SlotIndex is the slot index of the next non-debug instruction or the end
// of a BB, because DBG_VALUE's don't have slot index themselves.
// Adapted from RegisterCoalescer::buildVRegToDbgValueMap.
static DenseMap<Register, std::vector<std::pair<SlotIndex, MachineInstr *>>>
buildVRegToDbgValueMap(MachineFunction &MF, const LiveIntervals *Liveness) { … }

// After register coalescing, some DBG_VALUEs will be invalid. Set them undef.
// This function has to run before the actual coalescing, i.e., the register
// changes.
static void undefInvalidDbgValues(
    const LiveIntervals *Liveness,
    ArrayRef<SmallVector<LiveInterval *, 4>> Assignments,
    DenseMap<Register, std::vector<std::pair<SlotIndex, MachineInstr *>>>
        &DbgVRegToValues) { … }

bool WebAssemblyRegColoring::runOnMachineFunction(MachineFunction &MF) { … }