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[BlockPlacement] Add flag to disable profile usage #102956

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[BlockPlacement] Add flag to disable profile usage #102956

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22 changes: 14 additions & 8 deletions llvm/lib/CodeGen/MachineBlockPlacement.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -219,6 +219,10 @@ static cl::opt<unsigned> ExtTspBlockPlacementMaxBlocks(
"block placement."),
cl::init(UINT_MAX), cl::Hidden);

static cl::opt<bool>
UseProfileData("block-placement-use-profile", cl::init(true), cl::Hidden,
cl::desc("Use profile data to do precise benefit analysis"));

namespace llvm {
extern cl::opt<bool> EnableExtTspBlockPlacement;
extern cl::opt<bool> ApplyExtTspWithoutProfile;
Expand Down Expand Up @@ -1220,7 +1224,7 @@ bool MachineBlockPlacement::canTailDuplicateUnplacedPreds(

// If profile information is available, findDuplicateCandidates can do more
// precise benefit analysis.
if (F->getFunction().hasProfileData())
if (UseProfileData && F->getFunction().hasProfileData())
return true;

// This is mainly for function exit BB.
Expand Down Expand Up @@ -1388,7 +1392,7 @@ void MachineBlockPlacement::precomputeTriangleChains() {
// When profile is available, we need to handle the triangle-shape CFG.
static BranchProbability getLayoutSuccessorProbThreshold(
const MachineBasicBlock *BB) {
if (!BB->getParent()->getFunction().hasProfileData())
if (!UseProfileData || !BB->getParent()->getFunction().hasProfileData())
return BranchProbability(StaticLikelyProb, 100);
if (BB->succ_size() == 2) {
const MachineBasicBlock *Succ1 = *BB->succ_begin();
Expand Down Expand Up @@ -2621,7 +2625,8 @@ MachineBlockPlacement::collectLoopBlockSet(const MachineLoop &L) {
// will be merged into the first outer loop chain for which this block is not
// cold anymore. This needs precise profile data and we only do this when
// profile data is available.
if (F->getFunction().hasProfileData() || ForceLoopColdBlock) {
if ((UseProfileData && F->getFunction().hasProfileData()) ||
ForceLoopColdBlock) {
BlockFrequency LoopFreq(0);
for (auto *LoopPred : L.getHeader()->predecessors())
if (!L.contains(LoopPred))
Expand Down Expand Up @@ -2670,8 +2675,8 @@ void MachineBlockPlacement::buildLoopChains(const MachineLoop &L) {
// this loop by modeling costs more precisely which requires the profile data
// for better layout.
bool RotateLoopWithProfile =
ForcePreciseRotationCost ||
(PreciseRotationCost && F->getFunction().hasProfileData());
ForcePreciseRotationCost || (PreciseRotationCost && UseProfileData &&
F->getFunction().hasProfileData());

// First check to see if there is an obviously preferable top block for the
// loop. This will default to the header, but may end up as one of the
Expand Down Expand Up @@ -3208,7 +3213,7 @@ bool MachineBlockPlacement::maybeTailDuplicateBlock(
bool IsSimple = TailDup.isSimpleBB(BB);
SmallVector<MachineBasicBlock *, 8> CandidatePreds;
SmallVectorImpl<MachineBasicBlock *> *CandidatePtr = nullptr;
if (F->getFunction().hasProfileData()) {
if (UseProfileData && F->getFunction().hasProfileData()) {
// We can do partial duplication with precise profile information.
findDuplicateCandidates(CandidatePreds, BB, BlockFilter);
if (CandidatePreds.size() == 0)
Expand Down Expand Up @@ -3409,7 +3414,7 @@ void MachineBlockPlacement::findDuplicateCandidates(

void MachineBlockPlacement::initDupThreshold() {
DupThreshold = BlockFrequency(0);
if (!F->getFunction().hasProfileData())
if (!UseProfileData || !F->getFunction().hasProfileData())
return;

// We prefer to use prifile count.
Expand Down Expand Up @@ -3529,7 +3534,8 @@ bool MachineBlockPlacement::runOnMachineFunction(MachineFunction &MF) {

// Apply a post-processing optimizing block placement.
if (MF.size() >= 3 && EnableExtTspBlockPlacement &&
(ApplyExtTspWithoutProfile || MF.getFunction().hasProfileData()) &&
(ApplyExtTspWithoutProfile ||
(UseProfileData && MF.getFunction().hasProfileData())) &&
MF.size() <= ExtTspBlockPlacementMaxBlocks) {
// Find a new placement and modify the layout of the blocks in the function.
applyExtTsp();
Expand Down
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