0116ed0069
InstrRefBasedLDV is marginally slower than VarlocBasedLDV when analysing optimised code -- however, it's much slower when analysing code compiled -O0. To avoid this: don't use instruction referencing for -O0 functions. In the "pure" case of unoptimised code, this won't really harm the debugging experience because most variables won't have been promoted off the stack, so can't go missing. It becomes more complicated when optimised code is inlined into functions marked optnone; however these are rare, and as -O0 doesn't run many optimisations there should be little damage to the debug experience as a result. I've taken the opportunity to refactor testing for instruction-referencing into a MachineFunction method, which seems the most appropriate place to put it. Differential Revision: https://reviews.llvm.org/D108585
115 lines
3.9 KiB
C++
115 lines
3.9 KiB
C++
//===- LiveDebugValues.cpp - Tracking Debug Value MIs ---------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "LiveDebugValues.h"
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#include "llvm/CodeGen/MachineBasicBlock.h"
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#include "llvm/CodeGen/MachineFrameInfo.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/InitializePasses.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Target/TargetMachine.h"
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/// \file LiveDebugValues.cpp
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///
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/// The LiveDebugValues pass extends the range of variable locations
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/// (specified by DBG_VALUE instructions) from single blocks to successors
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/// and any other code locations where the variable location is valid.
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/// There are currently two implementations: the "VarLoc" implementation
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/// explicitly tracks the location of a variable, while the "InstrRef"
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/// implementation tracks the values defined by instructions through locations.
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///
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/// This file implements neither; it merely registers the pass, allows the
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/// user to pick which implementation will be used to propagate variable
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/// locations.
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#define DEBUG_TYPE "livedebugvalues"
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using namespace llvm;
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static cl::opt<bool>
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ForceInstrRefLDV("force-instr-ref-livedebugvalues", cl::Hidden,
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cl::desc("Use instruction-ref based LiveDebugValues with "
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"normal DBG_VALUE inputs"),
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cl::init(false));
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// Options to prevent pathological compile-time behavior. If InputBBLimit and
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// InputDbgValueLimit are both exceeded, range extension is disabled.
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static cl::opt<unsigned> InputBBLimit(
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"livedebugvalues-input-bb-limit",
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cl::desc("Maximum input basic blocks before DBG_VALUE limit applies"),
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cl::init(10000), cl::Hidden);
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static cl::opt<unsigned> InputDbgValueLimit(
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"livedebugvalues-input-dbg-value-limit",
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cl::desc(
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"Maximum input DBG_VALUE insts supported by debug range extension"),
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cl::init(50000), cl::Hidden);
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/// Generic LiveDebugValues pass. Calls through to VarLocBasedLDV or
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/// InstrRefBasedLDV to perform location propagation, via the LDVImpl
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/// base class.
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class LiveDebugValues : public MachineFunctionPass {
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public:
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static char ID;
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LiveDebugValues();
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~LiveDebugValues() {
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if (TheImpl)
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delete TheImpl;
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}
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/// Calculate the liveness information for the given machine function.
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bool runOnMachineFunction(MachineFunction &MF) override;
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MachineFunctionProperties getRequiredProperties() const override {
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return MachineFunctionProperties().set(
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MachineFunctionProperties::Property::NoVRegs);
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}
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void getAnalysisUsage(AnalysisUsage &AU) const override {
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AU.setPreservesCFG();
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MachineFunctionPass::getAnalysisUsage(AU);
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}
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private:
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LDVImpl *TheImpl;
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TargetPassConfig *TPC;
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};
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char LiveDebugValues::ID = 0;
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char &llvm::LiveDebugValuesID = LiveDebugValues::ID;
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INITIALIZE_PASS(LiveDebugValues, DEBUG_TYPE, "Live DEBUG_VALUE analysis", false,
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false)
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/// Default construct and initialize the pass.
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LiveDebugValues::LiveDebugValues() : MachineFunctionPass(ID) {
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initializeLiveDebugValuesPass(*PassRegistry::getPassRegistry());
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TheImpl = nullptr;
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}
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bool LiveDebugValues::runOnMachineFunction(MachineFunction &MF) {
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if (!TheImpl) {
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TPC = getAnalysisIfAvailable<TargetPassConfig>();
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bool InstrRefBased = MF.useDebugInstrRef();
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// Allow the user to force selection of InstrRef LDV.
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InstrRefBased |= ForceInstrRefLDV;
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if (InstrRefBased)
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TheImpl = llvm::makeInstrRefBasedLiveDebugValues();
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else
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TheImpl = llvm::makeVarLocBasedLiveDebugValues();
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}
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return TheImpl->ExtendRanges(MF, TPC, InputBBLimit, InputDbgValueLimit);
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}
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