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IfConversion: Improve doxygen comments 

llvm-svn: 278893
This commit is contained in:
Matthias Braun 2016-08-17 02:51:57 +00:00
parent f702d8ecb6
commit 2c931798d6
1 changed files with 46 additions and 63 deletions
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109
llvm/lib/CodeGen/IfConversion.cpp
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@ -85,7 +85,7 @@ namespace {
ICDiamond // BB is entry of a diamond sub-CFG.
};
/// BBInfo - One per MachineBasicBlock, this is used to cache the result
/// One per MachineBasicBlock, this is used to cache the result
/// if-conversion feasibility analysis. This includes results from
/// TargetInstrInfo::analyzeBranch() (i.e. TBB, FBB, and Cond), and its
/// classification, and common tail block of its successors (if it's a
@ -134,7 +134,7 @@ namespace {
FalseBB(nullptr) {}
};
/// IfcvtToken - Record information about pending if-conversions to attempt:
/// Record information about pending if-conversions to attempt:
/// BBI - Corresponding BBInfo.
/// Kind - Type of block. See IfcvtKind.
/// NeedSubsumption - True if the to-be-predicated BB has already been
@ -155,8 +155,8 @@ namespace {
: BBI(b), Kind(k), NeedSubsumption(s), NumDups(d), NumDups2(d2) {}
};
/// BBAnalysis - Results of if-conversion feasibility analysis indexed by
/// basic block number.
/// Results of if-conversion feasibility analysis indexed by basic block
/// number.
std::vector<BBInfo> BBAnalysis;
TargetSchedModel SchedModel;
@ -245,12 +245,12 @@ namespace {
Prediction);
}
// blockAlwaysFallThrough - Block ends without a terminator.
/// Returns true if Block ends without a terminator.
bool blockAlwaysFallThrough(BBInfo &BBI) const {
return BBI.IsBrAnalyzable && BBI.TrueBB == nullptr;
}
// IfcvtTokenCmp - Used to sort if-conversion candidates.
/// Used to sort if-conversion candidates.
static bool IfcvtTokenCmp(const std::unique_ptr<IfcvtToken> &C1,
const std::unique_ptr<IfcvtToken> &C2) {
int Incr1 = (C1->Kind == ICDiamond)
@ -438,8 +438,7 @@ bool IfConverter::runOnMachineFunction(MachineFunction &MF) {
return MadeChange;
}
/// findFalseBlock - BB has a fallthrough. Find its 'false' successor given
/// its 'true' successor.
/// BB has a fallthrough. Find its 'false' successor given its 'true' successor.
static MachineBasicBlock *findFalseBlock(MachineBasicBlock *BB,
MachineBasicBlock *TrueBB) {
for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(),
@ -451,8 +450,8 @@ static MachineBasicBlock *findFalseBlock(MachineBasicBlock *BB,
return nullptr;
}
/// ReverseBranchCondition - Reverse the condition of the end of the block
/// branch. Swap block's 'true' and 'false' successors.
/// Reverse the condition of the end of the block branch. Swap block's 'true'
/// and 'false' successors.
bool IfConverter::ReverseBranchCondition(BBInfo &BBI) const {
DebugLoc dl; // FIXME: this is nowhere
if (!TII->ReverseBranchCondition(BBI.BrCond)) {
@ -464,8 +463,8 @@ bool IfConverter::ReverseBranchCondition(BBInfo &BBI) const {
return false;
}
/// getNextBlock - Returns the next block in the function blocks ordering. If
/// it is the end, returns NULL.
/// Returns the next block in the function blocks ordering. If it is the end,
/// returns NULL.
static inline MachineBasicBlock *getNextBlock(MachineBasicBlock *BB) {
MachineFunction::iterator I = BB->getIterator();
MachineFunction::iterator E = BB->getParent()->end();
@ -474,10 +473,9 @@ static inline MachineBasicBlock *getNextBlock(MachineBasicBlock *BB) {
return &*I;
}
/// ValidSimple - Returns true if the 'true' block (along with its
/// predecessor) forms a valid simple shape for ifcvt. It also returns the
/// number of instructions that the ifcvt would need to duplicate if performed
/// in Dups.
/// Returns true if the 'true' block (along with its predecessor) forms a valid
/// simple shape for ifcvt. It also returns the number of instructions that the
/// ifcvt would need to duplicate if performed in Dups.
bool IfConverter::ValidSimple(BBInfo &TrueBBI, unsigned &Dups,
BranchProbability Prediction) const {
Dups = 0;
@ -498,12 +496,11 @@ bool IfConverter::ValidSimple(BBInfo &TrueBBI, unsigned &Dups,
return true;
}
/// ValidTriangle - Returns true if the 'true' and 'false' blocks (along
/// with their common predecessor) forms a valid triangle shape for ifcvt.
/// If 'FalseBranch' is true, it checks if 'true' block's false branch
/// branches to the 'false' block rather than the other way around. It also
/// returns the number of instructions that the ifcvt would need to duplicate
/// if performed in 'Dups'.
/// Returns true if the 'true' and 'false' blocks (along with their common
/// predecessor) forms a valid triangle shape for ifcvt. If 'FalseBranch' is
/// true, it checks if 'true' block's false branch branches to the 'false' block
/// rather than the other way around. It also returns the number of instructions
/// that the ifcvt would need to duplicate if performed in 'Dups'.
bool IfConverter::ValidTriangle(BBInfo &TrueBBI, BBInfo &FalseBBI,
bool FalseBranch, unsigned &Dups,
BranchProbability Prediction) const {
@ -543,7 +540,7 @@ bool IfConverter::ValidTriangle(BBInfo &TrueBBI, BBInfo &FalseBBI,
return TExit && TExit == FalseBBI.BB;
}
/// Increment It until it points to a non-debug instruction or to End.
/// Increment \p It until it points to a non-debug instruction or to \p End.
/// @param It Iterator to increment
/// @param End Iterator that points to end. Will be compared to It
/// @returns true if It == End, false otherwise.
@ -555,7 +552,7 @@ static inline bool skipDebugInstructionsForward(
return It == End;
}
/// Decrement It until it points to a non-debug instruction or to Begin.
/// Decrement \p It until it points to a non-debug instruction or to \p Begin.
/// @param It Iterator to decrement.
/// @param Begin Iterator that points to beginning. Will be compared to It
/// @returns true if It == Begin, false otherwise.
@ -811,8 +808,8 @@ void IfConverter::ScanInstructions(BBInfo &BBI,
}
}
/// FeasibilityAnalysis - Determine if the block is a suitable candidate to be
/// predicated by the specified predicate.
/// Determine if the block is a suitable candidate to be predicated by the
/// specified predicate.
bool IfConverter::FeasibilityAnalysis(BBInfo &BBI,
SmallVectorImpl<MachineOperand> &Pred,
bool isTriangle, bool RevBranch) {
@ -850,9 +847,8 @@ bool IfConverter::FeasibilityAnalysis(BBInfo &BBI,
return true;
}
/// AnalyzeBlock - Analyze the structure of the sub-CFG starting from
/// the specified block. Record its successors and whether it looks like an
/// if-conversion candidate.
/// Analyze the structure of the sub-CFG starting from the specified block.
/// Record its successors and whether it looks like an if-conversion candidate.
void IfConverter::AnalyzeBlock(
MachineBasicBlock *MBB, std::vector<std::unique_ptr<IfcvtToken>> &Tokens) {
struct BBState {
@ -1043,8 +1039,7 @@ void IfConverter::AnalyzeBlock(
}
}
/// AnalyzeBlocks - Analyze all blocks and find entries for all if-conversion
/// candidates.
/// Analyze all blocks and find entries for all if-conversion candidates.
void IfConverter::AnalyzeBlocks(
MachineFunction &MF, std::vector<std::unique_ptr<IfcvtToken>> &Tokens) {
for (auto &BB : MF)
@ -1054,9 +1049,8 @@ void IfConverter::AnalyzeBlocks(
std::stable_sort(Tokens.begin(), Tokens.end(), IfcvtTokenCmp);
}
/// canFallThroughTo - Returns true either if ToBB is the next block after BB or
/// that all the intervening blocks are empty (given BB can fall through to its
/// next block).
/// Returns true either if ToMBB is the next block after MBB or that all the
/// intervening blocks are empty (given MBB can fall through to its next block).
static bool canFallThroughTo(MachineBasicBlock *BB, MachineBasicBlock *ToBB) {
MachineFunction::iterator PI = BB->getIterator();
MachineFunction::iterator I = std::next(PI);
@ -1072,9 +1066,8 @@ static bool canFallThroughTo(MachineBasicBlock *BB, MachineBasicBlock *ToBB) {
return true;
}
/// InvalidatePreds - Invalidate predecessor BB info so it would be re-analyzed
/// to determine if it can be if-converted. If predecessor is already enqueued,
/// dequeue it!
/// Invalidate predecessor BB info so it would be re-analyzed to determine if it
/// can be if-converted. If predecessor is already enqueued, dequeue it!
void IfConverter::InvalidatePreds(MachineBasicBlock *BB) {
for (const auto &Predecessor : BB->predecessors()) {
BBInfo &PBBI = BBAnalysis[Predecessor->getNumber()];
@ -1085,8 +1078,7 @@ void IfConverter::InvalidatePreds(MachineBasicBlock *BB) {
}
}
/// InsertUncondBranch - Inserts an unconditional branch from BB to ToBB.
///
/// Inserts an unconditional branch from \p MBB to \p ToMBB.
static void InsertUncondBranch(MachineBasicBlock *BB, MachineBasicBlock *ToBB,
const TargetInstrInfo *TII) {
DebugLoc dl; // FIXME: this is nowhere
@ -1094,8 +1086,7 @@ static void InsertUncondBranch(MachineBasicBlock *BB, MachineBasicBlock *ToBB,
TII->InsertBranch(*BB, ToBB, nullptr, NoCond, dl);
}
/// RemoveExtraEdges - Remove true / false edges if either / both are no longer
/// successors.
/// Remove true / false edges if either / both are no longer successors.
void IfConverter::RemoveExtraEdges(BBInfo &BBI) {
MachineBasicBlock *TBB = nullptr, *FBB = nullptr;
SmallVector<MachineOperand, 4> Cond;
@ -1153,9 +1144,7 @@ static void UpdatePredRedefs(MachineInstr &MI, LivePhysRegs &Redefs) {
}
}
/**
* Remove kill flags from operands with a registers in the @p DontKill set.
*/
/// Remove kill flags from operands with a registers in the \p DontKill set.
static void RemoveKills(MachineInstr &MI, const LivePhysRegs &DontKill) {
for (MIBundleOperands O(MI); O.isValid(); ++O) {
if (!O->isReg() || !O->isKill())
@ -1165,10 +1154,8 @@ static void RemoveKills(MachineInstr &MI, const LivePhysRegs &DontKill) {
}
}
/**
* Walks a range of machine instructions and removes kill flags for registers
* in the @p DontKill set.
*/
/// Walks a range of machine instructions and removes kill flags for registers
/// in the \p DontKill set.
static void RemoveKills(MachineBasicBlock::iterator I,
MachineBasicBlock::iterator E,
const LivePhysRegs &DontKill,
@ -1177,8 +1164,7 @@ static void RemoveKills(MachineBasicBlock::iterator I,
RemoveKills(*I, DontKill);
}
/// IfConvertSimple - If convert a simple (split, no rejoin) sub-CFG.
///
/// If convert a simple (split, no rejoin) sub-CFG.
bool IfConverter::IfConvertSimple(BBInfo &BBI, IfcvtKind Kind) {
BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
@ -1263,8 +1249,7 @@ bool IfConverter::IfConvertSimple(BBInfo &BBI, IfcvtKind Kind) {
return true;
}
/// IfConvertTriangle - If convert a triangle sub-CFG.
///
/// If convert a triangle sub-CFG.
bool IfConverter::IfConvertTriangle(BBInfo &BBI, IfcvtKind Kind) {
BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
@ -1409,8 +1394,7 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI, IfcvtKind Kind) {
return true;
}
/// IfConvertDiamond - If convert a diamond sub-CFG.
///
/// If convert a diamond sub-CFG.
bool IfConverter::IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind,
unsigned NumDups1, unsigned NumDups2) {
BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
@ -1683,8 +1667,8 @@ static bool MaySpeculate(const MachineInstr &MI,
return true;
}
/// PredicateBlock - Predicate instructions from the start of the block to the
/// specified end with the specified condition.
/// Predicate instructions from the start of the block to the specified end with
/// the specified condition.
void IfConverter::PredicateBlock(BBInfo &BBI,
MachineBasicBlock::iterator E,
SmallVectorImpl<MachineOperand> &Cond,
@ -1726,8 +1710,8 @@ void IfConverter::PredicateBlock(BBInfo &BBI,
++NumUnpred;
}
/// CopyAndPredicateBlock - Copy and predicate instructions from source BB to
/// the destination block. Skip end of block branches if IgnoreBr is true.
/// Copy and predicate instructions from source BB to the destination block.
/// Skip end of block branches if IgnoreBr is true.
void IfConverter::CopyAndPredicateBlock(BBInfo &ToBBI, BBInfo &FromBBI,
SmallVectorImpl<MachineOperand> &Cond,
bool IgnoreBr) {
@ -1789,11 +1773,10 @@ void IfConverter::CopyAndPredicateBlock(BBInfo &ToBBI, BBInfo &FromBBI,
++NumDupBBs;
}
/// MergeBlocks - Move all instructions from FromBB to the end of ToBB.
/// This will leave FromBB as an empty block, so remove all of its
/// successor edges except for the fall-through edge. If AddEdges is true,
/// i.e., when FromBBI's branch is being moved, add those successor edges to
/// ToBBI.
/// Move all instructions from FromBB to the end of ToBB. This will leave
/// FromBB as an empty block, so remove all of its successor edges except for
/// the fall-through edge. If AddEdges is true, i.e., when FromBBI's branch is
/// being moved, add those successor edges to ToBBI.
void IfConverter::MergeBlocks(BBInfo &ToBBI, BBInfo &FromBBI, bool AddEdges) {
assert(!FromBBI.BB->hasAddressTaken() &&
"Removing a BB whose address is taken!");