LLVM  6.0.0svn
ConstantFold.cpp File Reference
#include "ConstantFold.h"
#include "llvm/ADT/APSInt.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GetElementPtrTypeIterator.h"
#include "llvm/IR/GlobalAlias.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Operator.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/ManagedStatic.h"
#include "llvm/Support/MathExtras.h"
Include dependency graph for ConstantFold.cpp:

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## Functions

static ConstantBitCastConstantVector (Constant *CV, VectorType *DstTy)
Convert the specified vector Constant node to the specified vector type. More...

static unsigned foldConstantCastPair (unsigned opc, ConstantExpr *Op, Type *DstTy)
This function determines which opcode to use to fold two constant cast expressions together. More...

static ConstantFoldBitCast (Constant *V, Type *DestTy)

static ConstantExtractConstantBytes (Constant *C, unsigned ByteStart, unsigned ByteSize)
V is an integer constant which only has a subset of its bytes used. More...

static ConstantgetFoldedSizeOf (Type *Ty, Type *DestTy, bool Folded)
Return a ConstantExpr with type DestTy for sizeof on Ty, with any known factors factored out. More...

static ConstantgetFoldedAlignOf (Type *Ty, Type *DestTy, bool Folded)
Return a ConstantExpr with type DestTy for alignof on Ty, with any known factors factored out. More...

static ConstantgetFoldedOffsetOf (Type *Ty, Constant *FieldNo, Type *DestTy, bool Folded)
Return a ConstantExpr with type DestTy for offsetof on Ty and FieldNo, with any known factors factored out. More...

static bool isMaybeZeroSizedType (Type *Ty)
This type is zero-sized if it's an array or structure of zero-sized types. More...

static int IdxCompare (Constant *C1, Constant *C2, Type *ElTy)
Compare the two constants as though they were getelementptr indices. More...

static FCmpInst::Predicate evaluateFCmpRelation (Constant *V1, Constant *V2)
This function determines if there is anything we can decide about the two constants provided. More...

static ICmpInst::Predicate areGlobalsPotentiallyEqual (const GlobalValue *GV1, const GlobalValue *GV2)

static ICmpInst::Predicate evaluateICmpRelation (Constant *V1, Constant *V2, bool isSigned)
This function determines if there is anything we can decide about the two constants provided. More...

template<typename IndexTy >
static bool isInBoundsIndices (ArrayRef< IndexTy > Idxs)
Test whether the given sequence of normalized indices is "inbounds". More...

static bool isIndexInRangeOfArrayType (uint64_t NumElements, const ConstantInt *CI)
Test whether a given ConstantInt is in-range for a SequentialType. More...

## ◆ areGlobalsPotentiallyEqual()

 static ICmpInst::Predicate areGlobalsPotentiallyEqual ( const GlobalValue * GV1, const GlobalValue * GV2 )
static

Definition at line 1405 of file ConstantFold.cpp.

Referenced by evaluateICmpRelation().

## ◆ BitCastConstantVector()

 static Constant* BitCastConstantVector ( Constant * CV, VectorType * DstTy )
static

Convert the specified vector Constant node to the specified vector type.

At this point, we know that the elements of the input vector constant are all simple integer or FP values.

Definition at line 45 of file ConstantFold.cpp.

Referenced by FoldBitCast().

## ◆ evaluateFCmpRelation()

 static FCmpInst::Predicate evaluateFCmpRelation ( Constant * V1, Constant * V2 )
static

This function determines if there is anything we can decide about the two constants provided.

This doesn't need to handle simple things like ConstantFP comparisons, but should instead handle ConstantExprs. If we can determine that the two constants have a particular relation to each other, we should return the corresponding FCmpInst predicate, otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in ConstantFoldCompareInstruction.

To simplify this code we canonicalize the relation so that the first operand is always the most "complex" of the two. We consider ConstantFP to be the simplest, and ConstantExprs to be the most complex.

Definition at line 1353 of file ConstantFold.cpp.

Referenced by llvm::ConstantFoldCompareInstruction().

## ◆ evaluateICmpRelation()

 static ICmpInst::Predicate evaluateICmpRelation ( Constant * V1, Constant * V2, bool isSigned )
static

This function determines if there is anything we can decide about the two constants provided.

This doesn't need to handle simple things like integer comparisons, but should instead handle ConstantExprs and GlobalValues. If we can determine that the two constants have a particular relation to each other, we should return the corresponding ICmp predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE.

To simplify this code we canonicalize the relation so that the first operand is always the most "complex" of the two. We consider simple constants (like ConstantInt) to be the simplest, followed by GlobalValues, followed by ConstantExpr's (the most complex).

Definition at line 1441 of file ConstantFold.cpp.

Referenced by llvm::ConstantFoldCompareInstruction().

## ◆ ExtractConstantBytes()

 static Constant* ExtractConstantBytes ( Constant * C, unsigned ByteStart, unsigned ByteSize )
static

V is an integer constant which only has a subset of its bytes used.

The bytes used are indicated by ByteStart (which is the first byte used, counting from the least significant byte) and ByteSize, which is the number of bytes used.

This function analyzes the specified constant to see if the specified byte range can be returned as a simplified constant. If so, the constant is returned, otherwise null is returned.

Definition at line 212 of file ConstantFold.cpp.

Referenced by llvm::ConstantFoldCastInstruction().

## ◆ FoldBitCast()

 static Constant* FoldBitCast ( Constant * V, Type * DestTy )
static

## ◆ foldConstantCastPair()

 static unsigned foldConstantCastPair ( unsigned opc, ConstantExpr * Op, Type * DstTy )
static

This function determines which opcode to use to fold two constant cast expressions together.

It uses CastInst::isEliminableCastPair to determine the opcode. Consequently its just a wrapper around that function. Determine if it is valid to fold a cast of a cast

Parameters
 opc opcode of the second cast constant expression Op the first cast constant expression DstTy destination type of the first cast

Definition at line 76 of file ConstantFold.cpp.

Referenced by llvm::ConstantFoldCastInstruction().

## ◆ getFoldedAlignOf()

 static Constant* getFoldedAlignOf ( Type * Ty, Type * DestTy, bool Folded )
static

Return a ConstantExpr with type DestTy for alignof on Ty, with any known factors factored out.

If Folded is false, return null if no factoring was possible, to avoid endlessly bouncing an unfoldable expression back into the top-level folder.

Definition at line 406 of file ConstantFold.cpp.

Referenced by llvm::ConstantFoldCastInstruction().

## ◆ getFoldedOffsetOf()

 static Constant* getFoldedOffsetOf ( Type * Ty, Constant * FieldNo, Type * DestTy, bool Folded )
static

Return a ConstantExpr with type DestTy for offsetof on Ty and FieldNo, with any known factors factored out.

If Folded is false, return null if no factoring was possible, to avoid endlessly bouncing an unfoldable expression back into the top-level folder.

Definition at line 470 of file ConstantFold.cpp.

Referenced by llvm::ConstantFoldCastInstruction().

## ◆ getFoldedSizeOf()

 static Constant* getFoldedSizeOf ( Type * Ty, Type * DestTy, bool Folded )
static

Return a ConstantExpr with type DestTy for sizeof on Ty, with any known factors factored out.

If Folded is false, return null if no factoring was possible, to avoid endlessly bouncing an unfoldable expression back into the top-level folder.

Definition at line 351 of file ConstantFold.cpp.

Referenced by llvm::ConstantFoldCastInstruction(), and getFoldedOffsetOf().

## ◆ IdxCompare()

 static int IdxCompare ( Constant * C1, Constant * C2, Type * ElTy )
static

Compare the two constants as though they were getelementptr indices.

This allows coercion of the types to be the same thing.

If the two constants are the "same" (after coercion), return 0. If the first is less than the second, return -1, if the second is less than the first, return 1. If the constants are not integral, return -2.

Definition at line 1309 of file ConstantFold.cpp.

References isMaybeZeroSizedType().

Referenced by evaluateICmpRelation().

## ◆ isInBoundsIndices()

template<typename IndexTy >
 static bool isInBoundsIndices ( ArrayRef< IndexTy > Idxs )
static

Test whether the given sequence of normalized indices is "inbounds".

Definition at line 2011 of file ConstantFold.cpp.

References llvm::ArrayRef< T >::empty(), and llvm::ArrayRef< T >::size().

Referenced by llvm::ConstantFoldGetElementPtr().

## ◆ isIndexInRangeOfArrayType()

 static bool isIndexInRangeOfArrayType ( uint64_t NumElements, const ConstantInt * CI )
static

Test whether a given ConstantInt is in-range for a SequentialType.

Definition at line 2029 of file ConstantFold.cpp.

Referenced by llvm::ConstantFoldGetElementPtr().

## ◆ isMaybeZeroSizedType()

 static bool isMaybeZeroSizedType ( Type * Ty )
static

This type is zero-sized if it's an array or structure of zero-sized types.

The only leaf zero-sized type is an empty structure.

Definition at line 1287 of file ConstantFold.cpp.

Referenced by IdxCompare().