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[PM] Clean up a bunch of the doxygen / API docs on the InstCombiner pass

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prior to refactoring it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226594 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chandler Carruth 2015-01-20 19:27:58 +00:00
parent 0d12d4ebc6
commit 5761a8e4f3
1 changed files with 61 additions and 50 deletions
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111
lib/Transforms/InstCombine/InstCombine.h
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@ -35,8 +35,7 @@ class DbgDeclareInst;
class MemIntrinsic;
class MemSetInst;
/// SelectPatternFlavor - We can match a variety of different patterns for
/// select operations.
/// \brief Specific patterns of select instructions we can match.
enum SelectPatternFlavor {
SPF_UNKNOWN = 0,
SPF_SMIN,
@ -47,8 +46,15 @@ enum SelectPatternFlavor {
SPF_NABS
};
/// getComplexity: Assign a complexity or rank value to LLVM Values...
/// 0 -> undef, 1 -> Const, 2 -> Other, 3 -> Arg, 3 -> Unary, 4 -> OtherInst
/// \brief Assign a complexity or rank value to LLVM Values.
///
/// This routine maps IR values to various complexity ranks:
/// 0 -> undef
/// 1 -> Constants
/// 2 -> Other non-instructions
/// 3 -> Arguments
/// 3 -> Unary operations
/// 4 -> Other instructions
static inline unsigned getComplexity(Value *V) {
if (isa<Instruction>(V)) {
if (BinaryOperator::isNeg(V) || BinaryOperator::isFNeg(V) ||
@ -61,18 +67,17 @@ static inline unsigned getComplexity(Value *V) {
return isa<Constant>(V) ? (isa<UndefValue>(V) ? 0 : 1) : 2;
}
/// AddOne - Add one to a Constant
/// \brief Add one to a Constant
static inline Constant *AddOne(Constant *C) {
return ConstantExpr::getAdd(C, ConstantInt::get(C->getType(), 1));
}
/// SubOne - Subtract one from a Constant
/// \brief Subtract one from a Constant
static inline Constant *SubOne(Constant *C) {
return ConstantExpr::getSub(C, ConstantInt::get(C->getType(), 1));
}
/// InstCombineIRInserter - This is an IRBuilder insertion helper that works
/// just like the normal insertion helper, but also adds any new instructions
/// to the instcombine worklist.
/// \brief An IRBuilder inserter that adds new instructions to the instcombine
/// worklist.
class LLVM_LIBRARY_VISIBILITY InstCombineIRInserter
: public IRBuilderDefaultInserter<true> {
InstCombineWorklist &Worklist;
@ -93,7 +98,11 @@ public:
}
};
/// InstCombiner - The -instcombine pass.
/// \brief The core instruction combiner logic.
///
/// This class provides both the logic to recursively visit instructions and
/// combine them, as well as the pass infrastructure for running this as part
/// of the LLVM pass pipeline.
class LLVM_LIBRARY_VISIBILITY InstCombiner
: public FunctionPass,
public InstVisitor<InstCombiner, Instruction *> {
@ -107,11 +116,11 @@ class LLVM_LIBRARY_VISIBILITY InstCombiner
bool MinimizeSize;
public:
/// Worklist - All of the instructions that need to be simplified.
/// \brief A worklist of the instructions that need to be simplified.
InstCombineWorklist Worklist;
/// Builder - This is an IRBuilder that automatically inserts new
/// instructions into the worklist when they are created.
/// \brief An IRBuilder that automatically inserts new instructions into the
/// worklist.
typedef IRBuilder<true, TargetFolder, InstCombineIRInserter> BuilderTy;
BuilderTy *Builder;
@ -271,10 +280,12 @@ private:
SmallVectorImpl<Value *> &NewIndices);
Instruction *FoldOpIntoSelect(Instruction &Op, SelectInst *SI);
/// ShouldOptimizeCast - Return true if the cast from "V to Ty" actually
/// results in any code being generated and is interesting to optimize out. If
/// the cast can be eliminated by some other simple transformation, we prefer
/// to do the simplification first.
/// \brief Classify whether a cast is worth optimizing.
///
/// Returns true if the cast from "V to Ty" actually results in any code
/// being generated and is interesting to optimize out. If the cast can be
/// eliminated by some other simple transformation, we prefer to do the
/// simplification first.
bool ShouldOptimizeCast(Instruction::CastOps opcode, const Value *V,
Type *Ty);
@ -295,9 +306,10 @@ private:
Value *EvaluateInDifferentElementOrder(Value *V, ArrayRef<int> Mask);
public:
// InsertNewInstBefore - insert an instruction New before instruction Old
// in the program. Add the new instruction to the worklist.
//
/// \brief Inserts an instruction \p New before instruction \p Old
///
/// Also adds the new instruction to the worklist and returns \p New so that
/// it is suitable for use as the return from the visitation patterns.
Instruction *InsertNewInstBefore(Instruction *New, Instruction &Old) {
assert(New && !New->getParent() &&
"New instruction already inserted into a basic block!");
@ -307,20 +319,18 @@ public:
return New;
}
// InsertNewInstWith - same as InsertNewInstBefore, but also sets the
// debug loc.
//
/// \brief Same as InsertNewInstBefore, but also sets the debug loc.
Instruction *InsertNewInstWith(Instruction *New, Instruction &Old) {
New->setDebugLoc(Old.getDebugLoc());
return InsertNewInstBefore(New, Old);
}
// ReplaceInstUsesWith - This method is to be used when an instruction is
// found to be dead, replacable with another preexisting expression. Here
// we add all uses of I to the worklist, replace all uses of I with the new
// value, then return I, so that the inst combiner will know that I was
// modified.
//
/// \brief A combiner-aware RAUW-like routine.
///
/// This method is to be used when an instruction is found to be dead,
/// replacable with another preexisting expression. Here we add all uses of
/// I to the worklist, replace all uses of I with the new value, then return
/// I, so that the inst combiner will know that I was modified.
Instruction *ReplaceInstUsesWith(Instruction &I, Value *V) {
Worklist.AddUsersToWorkList(I); // Add all modified instrs to worklist.
@ -350,10 +360,11 @@ public:
return InsertValueInst::Create(Struct, Result, 0);
}
// EraseInstFromFunction - When dealing with an instruction that has side
// effects or produces a void value, we can't rely on DCE to delete the
// instruction. Instead, visit methods should return the value returned by
// this function.
/// \brief Combiner aware instruction erasure.
///
/// When dealing with an instruction that has side effects or produces a void
/// value, we can't rely on DCE to delete the instruction. Instead, visit
/// methods should return the value returned by this function.
Instruction *EraseInstFromFunction(Instruction &I) {
DEBUG(dbgs() << "IC: ERASE " << I << '\n');
@ -401,19 +412,20 @@ public:
}
private:
/// SimplifyAssociativeOrCommutative - This performs a few simplifications for
/// operators which are associative or commutative.
/// \brief Performs a few simplifications for operators which are associative
/// or commutative.
bool SimplifyAssociativeOrCommutative(BinaryOperator &I);
/// SimplifyUsingDistributiveLaws - This tries to simplify binary operations
/// which some other binary operation distributes over either by factorizing
/// out common terms (eg "(A*B)+(A*C)" -> "A*(B+C)") or expanding out if this
/// results in simplifications (eg: "A & (B | C) -> (A&B) | (A&C)" if this is
/// a win). Returns the simplified value, or null if it didn't simplify.
/// \brief Tries to simplify binary operations which some other binary operation distributes over.
///
/// It does this by either by factorizing out common terms (eg "(A*B)+(A*C)"
/// -> "A*(B+C)") or expanding out if this results in simplifications (eg: "A
/// & (B | C) -> (A&B) | (A&C)" if this is a win). Returns the simplified
/// value, or null if it didn't simplify.
Value *SimplifyUsingDistributiveLaws(BinaryOperator &I);
/// SimplifyDemandedUseBits - Attempts to replace V with a simpler value
/// based on the demanded bits.
/// \brief Attempts to replace V with a simpler value based on the demanded
/// bits.
Value *SimplifyDemandedUseBits(Value *V, APInt DemandedMask, APInt &KnownZero,
APInt &KnownOne, unsigned Depth,
Instruction *CxtI = nullptr);
@ -425,9 +437,8 @@ private:
APInt DemandedMask, APInt &KnownZero,
APInt &KnownOne);
/// SimplifyDemandedInstructionBits - Inst is an integer instruction that
/// SimplifyDemandedBits knows about. See if the instruction has any
/// properties that allow us to simplify its operands.
/// \brief Tries to simplify operands to an integer instruction based on its
/// demanded bits.
bool SimplifyDemandedInstructionBits(Instruction &Inst);
Value *SimplifyDemandedVectorElts(Value *V, APInt DemandedElts,
@ -443,9 +454,8 @@ private:
//
Instruction *FoldOpIntoPhi(Instruction &I);
// FoldPHIArgOpIntoPHI - If all operands to a PHI node are the same "unary"
// operator and they all are only used by the PHI, PHI together their
// inputs, and do the operation once, to the result of the PHI.
/// \brief Try to rotate an operation below a PHI node, using PHI nodes for
/// its operands.
Instruction *FoldPHIArgOpIntoPHI(PHINode &PN);
Instruction *FoldPHIArgBinOpIntoPHI(PHINode &PN);
Instruction *FoldPHIArgGEPIntoPHI(PHINode &PN);
@ -466,8 +476,9 @@ private:
Value *EvaluateInDifferentType(Value *V, Type *Ty, bool isSigned);
/// Descale - Return a value X such that Val = X * Scale, or null if none. If
/// the multiplication is known not to overflow then NoSignedWrap is set.
/// \brief Returns a value X such that Val = X * Scale, or null if none.
///
/// If the multiplication is known not to overflow then NoSignedWrap is set.
Value *Descale(Value *Val, APInt Scale, bool &NoSignedWrap);
};