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llvm-6502/lib/Analysis/ConstantFolding.cpp
Nick Lewycky 3dfd7bf511 "ret (constexpr)" can't be folded into a Constant. Add a method to 
Analysis/ConstantFolding to fold ConstantExpr's, then make instcombine use it
to try to use targetdata to fold constant expressions on void instructions.

Also extend the icmp(inttoptr, inttoptr) folding to handle the case where
int size != ptr size.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@51559 91177308-0d34-0410-b5e6-96231b3b80d8
2008-05-25 20:56:15 +00:00

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//===-- ConstantFolding.cpp - Analyze constant folding possibilities ------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This family of functions determines the possibility of performing constant
// folding.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
#include "llvm/Instructions.h"
#include "llvm/Intrinsics.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Support/MathExtras.h"
#include <cerrno>
#include <cmath>
using namespace llvm;
//===----------------------------------------------------------------------===//
// Constant Folding internal helper functions
//===----------------------------------------------------------------------===//
/// IsConstantOffsetFromGlobal - If this constant is actually a constant offset
/// from a global, return the global and the constant. Because of
/// constantexprs, this function is recursive.
static bool IsConstantOffsetFromGlobal(Constant *C, GlobalValue *&GV,
int64_t &Offset, const TargetData &TD) {
// Trivial case, constant is the global.
if ((GV = dyn_cast<GlobalValue>(C))) {
Offset = 0;
return true;
}
// Otherwise, if this isn't a constant expr, bail out.
ConstantExpr *CE = dyn_cast<ConstantExpr>(C);
if (!CE) return false;
// Look through ptr->int and ptr->ptr casts.
if (CE->getOpcode() == Instruction::PtrToInt ||
CE->getOpcode() == Instruction::BitCast)
return IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD);
// i32* getelementptr ([5 x i32]* @a, i32 0, i32 5)
if (CE->getOpcode() == Instruction::GetElementPtr) {
// Cannot compute this if the element type of the pointer is missing size
// info.
if (!cast<PointerType>(CE->getOperand(0)->getType())
->getElementType()->isSized())
return false;
// If the base isn't a global+constant, we aren't either.
if (!IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD))
return false;
// Otherwise, add any offset that our operands provide.
gep_type_iterator GTI = gep_type_begin(CE);
for (User::const_op_iterator i = CE->op_begin() + 1, e = CE->op_end();
i != e; ++i, ++GTI) {
ConstantInt *CI = dyn_cast<ConstantInt>(*i);
if (!CI) return false; // Index isn't a simple constant?
if (CI->getZExtValue() == 0) continue; // Not adding anything.
if (const StructType *ST = dyn_cast<StructType>(*GTI)) {
// N = N + Offset
Offset += TD.getStructLayout(ST)->getElementOffset(CI->getZExtValue());
} else {
const SequentialType *SQT = cast<SequentialType>(*GTI);
Offset += TD.getABITypeSize(SQT->getElementType())*CI->getSExtValue();
}
}
return true;
}
return false;
}
/// SymbolicallyEvaluateBinop - One of Op0/Op1 is a constant expression.
/// Attempt to symbolically evaluate the result of a binary operator merging
/// these together. If target data info is available, it is provided as TD,
/// otherwise TD is null.
static Constant *SymbolicallyEvaluateBinop(unsigned Opc, Constant *Op0,
Constant *Op1, const TargetData *TD){
// SROA
// Fold (and 0xffffffff00000000, (shl x, 32)) -> shl.
// Fold (lshr (or X, Y), 32) -> (lshr [X/Y], 32) if one doesn't contribute
// bits.
// If the constant expr is something like &A[123] - &A[4].f, fold this into a
// constant. This happens frequently when iterating over a global array.
if (Opc == Instruction::Sub && TD) {
GlobalValue *GV1, *GV2;
int64_t Offs1, Offs2;
if (IsConstantOffsetFromGlobal(Op0, GV1, Offs1, *TD))
if (IsConstantOffsetFromGlobal(Op1, GV2, Offs2, *TD) &&
GV1 == GV2) {
// (&GV+C1) - (&GV+C2) -> C1-C2, pointer arithmetic cannot overflow.
return ConstantInt::get(Op0->getType(), Offs1-Offs2);
}
}
// TODO: Fold icmp setne/seteq as well.
return 0;
}
/// SymbolicallyEvaluateGEP - If we can symbolically evaluate the specified GEP
/// constant expression, do so.
static Constant *SymbolicallyEvaluateGEP(Constant* const* Ops, unsigned NumOps,
const Type *ResultTy,
const TargetData *TD) {
Constant *Ptr = Ops[0];
if (!TD || !cast<PointerType>(Ptr->getType())->getElementType()->isSized())
return 0;
uint64_t BasePtr = 0;
if (!Ptr->isNullValue()) {
// If this is a inttoptr from a constant int, we can fold this as the base,
// otherwise we can't.
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
if (CE->getOpcode() == Instruction::IntToPtr)
if (ConstantInt *Base = dyn_cast<ConstantInt>(CE->getOperand(0)))
BasePtr = Base->getZExtValue();
if (BasePtr == 0)
return 0;
}
// If this is a constant expr gep that is effectively computing an
// "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12'
for (unsigned i = 1; i != NumOps; ++i)
if (!isa<ConstantInt>(Ops[i]))
return false;
uint64_t Offset = TD->getIndexedOffset(Ptr->getType(),
(Value**)Ops+1, NumOps-1);
Constant *C = ConstantInt::get(TD->getIntPtrType(), Offset+BasePtr);
return ConstantExpr::getIntToPtr(C, ResultTy);
}
/// FoldBitCast - Constant fold bitcast, symbolically evaluating it with
/// targetdata. Return 0 if unfoldable.
static Constant *FoldBitCast(Constant *C, const Type *DestTy,
const TargetData &TD) {
// If this is a bitcast from constant vector -> vector, fold it.
if (ConstantVector *CV = dyn_cast<ConstantVector>(C)) {
if (const VectorType *DestVTy = dyn_cast<VectorType>(DestTy)) {
// If the element types match, VMCore can fold it.
unsigned NumDstElt = DestVTy->getNumElements();
unsigned NumSrcElt = CV->getNumOperands();
if (NumDstElt == NumSrcElt)
return 0;
const Type *SrcEltTy = CV->getType()->getElementType();
const Type *DstEltTy = DestVTy->getElementType();
// Otherwise, we're changing the number of elements in a vector, which
// requires endianness information to do the right thing. For example,
// bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
// folds to (little endian):
// <4 x i32> <i32 0, i32 0, i32 1, i32 0>
// and to (big endian):
// <4 x i32> <i32 0, i32 0, i32 0, i32 1>
// First thing is first. We only want to think about integer here, so if
// we have something in FP form, recast it as integer.
if (DstEltTy->isFloatingPoint()) {
// Fold to an vector of integers with same size as our FP type.
unsigned FPWidth = DstEltTy->getPrimitiveSizeInBits();
const Type *DestIVTy = VectorType::get(IntegerType::get(FPWidth),
NumDstElt);
// Recursively handle this integer conversion, if possible.
C = FoldBitCast(C, DestIVTy, TD);
if (!C) return 0;
// Finally, VMCore can handle this now that #elts line up.
return ConstantExpr::getBitCast(C, DestTy);
}
// Okay, we know the destination is integer, if the input is FP, convert
// it to integer first.
if (SrcEltTy->isFloatingPoint()) {
unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits();
const Type *SrcIVTy = VectorType::get(IntegerType::get(FPWidth),
NumSrcElt);
// Ask VMCore to do the conversion now that #elts line up.
C = ConstantExpr::getBitCast(C, SrcIVTy);
CV = dyn_cast<ConstantVector>(C);
if (!CV) return 0; // If VMCore wasn't able to fold it, bail out.
}
// Now we know that the input and output vectors are both integer vectors
// of the same size, and that their #elements is not the same. Do the
// conversion here, which depends on whether the input or output has
// more elements.
bool isLittleEndian = TD.isLittleEndian();
SmallVector<Constant*, 32> Result;
if (NumDstElt < NumSrcElt) {
// Handle: bitcast (<4 x i32> <i32 0, i32 1, i32 2, i32 3> to <2 x i64>)
Constant *Zero = Constant::getNullValue(DstEltTy);
unsigned Ratio = NumSrcElt/NumDstElt;
unsigned SrcBitSize = SrcEltTy->getPrimitiveSizeInBits();
unsigned SrcElt = 0;
for (unsigned i = 0; i != NumDstElt; ++i) {
// Build each element of the result.
Constant *Elt = Zero;
unsigned ShiftAmt = isLittleEndian ? 0 : SrcBitSize*(Ratio-1);
for (unsigned j = 0; j != Ratio; ++j) {
Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(SrcElt++));
if (!Src) return 0; // Reject constantexpr elements.
// Zero extend the element to the right size.
Src = ConstantExpr::getZExt(Src, Elt->getType());
// Shift it to the right place, depending on endianness.
Src = ConstantExpr::getShl(Src,
ConstantInt::get(Src->getType(), ShiftAmt));
ShiftAmt += isLittleEndian ? SrcBitSize : -SrcBitSize;
// Mix it in.
Elt = ConstantExpr::getOr(Elt, Src);
}
Result.push_back(Elt);
}
} else {
// Handle: bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
unsigned Ratio = NumDstElt/NumSrcElt;
unsigned DstBitSize = DstEltTy->getPrimitiveSizeInBits();
// Loop over each source value, expanding into multiple results.
for (unsigned i = 0; i != NumSrcElt; ++i) {
Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(i));
if (!Src) return 0; // Reject constantexpr elements.
unsigned ShiftAmt = isLittleEndian ? 0 : DstBitSize*(Ratio-1);
for (unsigned j = 0; j != Ratio; ++j) {
// Shift the piece of the value into the right place, depending on
// endianness.
Constant *Elt = ConstantExpr::getLShr(Src,
ConstantInt::get(Src->getType(), ShiftAmt));
ShiftAmt += isLittleEndian ? DstBitSize : -DstBitSize;
// Truncate and remember this piece.
Result.push_back(ConstantExpr::getTrunc(Elt, DstEltTy));
}
}
}
return ConstantVector::get(&Result[0], Result.size());
}
}
return 0;
}
//===----------------------------------------------------------------------===//
// Constant Folding public APIs
//===----------------------------------------------------------------------===//
/// ConstantFoldInstruction - Attempt to constant fold the specified
/// instruction. If successful, the constant result is returned, if not, null
/// is returned. Note that this function can only fail when attempting to fold
/// instructions like loads and stores, which have no constant expression form.
///
Constant *llvm::ConstantFoldInstruction(Instruction *I, const TargetData *TD) {
if (PHINode *PN = dyn_cast<PHINode>(I)) {
if (PN->getNumIncomingValues() == 0)
return Constant::getNullValue(PN->getType());
Constant *Result = dyn_cast<Constant>(PN->getIncomingValue(0));
if (Result == 0) return 0;
// Handle PHI nodes specially here...
for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i)
if (PN->getIncomingValue(i) != Result && PN->getIncomingValue(i) != PN)
return 0; // Not all the same incoming constants...
// If we reach here, all incoming values are the same constant.
return Result;
}
// Scan the operand list, checking to see if they are all constants, if so,
// hand off to ConstantFoldInstOperands.
SmallVector<Constant*, 8> Ops;
for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i)
if (Constant *Op = dyn_cast<Constant>(*i))
Ops.push_back(Op);
else
return 0; // All operands not constant!
if (const CmpInst *CI = dyn_cast<CmpInst>(I))
return ConstantFoldCompareInstOperands(CI->getPredicate(),
&Ops[0], Ops.size(), TD);
else
return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
&Ops[0], Ops.size(), TD);
}
/// ConstantFoldConstantExpression - Attempt to fold the constant expression
/// using the specified TargetData. If successful, the constant result is
/// result is returned, if not, null is returned.
Constant *llvm::ConstantFoldConstantExpression(ConstantExpr *CE,
const TargetData *TD) {
assert(TD && "ConstantFoldConstantExpression requires a valid TargetData.");
SmallVector<Constant*, 8> Ops;
for (User::op_iterator i = CE->op_begin(), e = CE->op_end(); i != e; ++i)
Ops.push_back(cast<Constant>(*i));
if (CE->isCompare())
return ConstantFoldCompareInstOperands(CE->getPredicate(),
&Ops[0], Ops.size(), TD);
else
return ConstantFoldInstOperands(CE->getOpcode(), CE->getType(),
&Ops[0], Ops.size(), TD);
}
/// ConstantFoldInstOperands - Attempt to constant fold an instruction with the
/// specified opcode and operands. If successful, the constant result is
/// returned, if not, null is returned. Note that this function can fail when
/// attempting to fold instructions like loads and stores, which have no
/// constant expression form.
///
Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, const Type *DestTy,
Constant* const* Ops, unsigned NumOps,
const TargetData *TD) {
// Handle easy binops first.
if (Instruction::isBinaryOp(Opcode)) {
if (isa<ConstantExpr>(Ops[0]) || isa<ConstantExpr>(Ops[1]))
if (Constant *C = SymbolicallyEvaluateBinop(Opcode, Ops[0], Ops[1], TD))
return C;
return ConstantExpr::get(Opcode, Ops[0], Ops[1]);
}
switch (Opcode) {
default: return 0;
case Instruction::Call:
if (Function *F = dyn_cast<Function>(Ops[0]))
if (canConstantFoldCallTo(F))
return ConstantFoldCall(F, Ops+1, NumOps-1);
return 0;
case Instruction::ICmp:
case Instruction::FCmp:
assert(0 &&"This function is invalid for compares: no predicate specified");
case Instruction::PtrToInt:
// If the input is a inttoptr, eliminate the pair. This requires knowing
// the width of a pointer, so it can't be done in ConstantExpr::getCast.
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) {
if (TD && CE->getOpcode() == Instruction::IntToPtr) {
Constant *Input = CE->getOperand(0);
unsigned InWidth = Input->getType()->getPrimitiveSizeInBits();
Constant *Mask =
ConstantInt::get(APInt::getLowBitsSet(InWidth,
TD->getPointerSizeInBits()));
Input = ConstantExpr::getAnd(Input, Mask);
// Do a zext or trunc to get to the dest size.
return ConstantExpr::getIntegerCast(Input, DestTy, false);
}
}
return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
case Instruction::IntToPtr:
case Instruction::Trunc:
case Instruction::ZExt:
case Instruction::SExt:
case Instruction::FPTrunc:
case Instruction::FPExt:
case Instruction::UIToFP:
case Instruction::SIToFP:
case Instruction::FPToUI:
case Instruction::FPToSI:
return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
case Instruction::BitCast:
if (TD)
if (Constant *C = FoldBitCast(Ops[0], DestTy, *TD))
return C;
return ConstantExpr::getBitCast(Ops[0], DestTy);
case Instruction::Select:
return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]);
case Instruction::ExtractElement:
return ConstantExpr::getExtractElement(Ops[0], Ops[1]);
case Instruction::InsertElement:
return ConstantExpr::getInsertElement(Ops[0], Ops[1], Ops[2]);
case Instruction::ShuffleVector:
return ConstantExpr::getShuffleVector(Ops[0], Ops[1], Ops[2]);
case Instruction::GetElementPtr:
if (Constant *C = SymbolicallyEvaluateGEP(Ops, NumOps, DestTy, TD))
return C;
return ConstantExpr::getGetElementPtr(Ops[0], Ops+1, NumOps-1);
}
}
/// ConstantFoldCompareInstOperands - Attempt to constant fold a compare
/// instruction (icmp/fcmp) with the specified operands. If it fails, it
/// returns a constant expression of the specified operands.
///
Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate,
Constant*const * Ops,
unsigned NumOps,
const TargetData *TD) {
// fold: icmp (inttoptr x), null -> icmp x, 0
// fold: icmp (ptrtoint x), 0 -> icmp x, null
// fold: icmp (inttoptr x), (inttoptr y) -> icmp trunc/zext x, trunc/zext y
// fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y
//
// ConstantExpr::getCompare cannot do this, because it doesn't have TD
// around to know if bit truncation is happening.
if (ConstantExpr *CE0 = dyn_cast<ConstantExpr>(Ops[0])) {
if (TD && Ops[1]->isNullValue()) {
const Type *IntPtrTy = TD->getIntPtrType();
if (CE0->getOpcode() == Instruction::IntToPtr) {
// Convert the integer value to the right size to ensure we get the
// proper extension or truncation.
Constant *C = ConstantExpr::getIntegerCast(CE0->getOperand(0),
IntPtrTy, false);
Constant *NewOps[] = { C, Constant::getNullValue(C->getType()) };
return ConstantFoldCompareInstOperands(Predicate, NewOps, 2, TD);
}
// Only do this transformation if the int is intptrty in size, otherwise
// there is a truncation or extension that we aren't modeling.
if (CE0->getOpcode() == Instruction::PtrToInt &&
CE0->getType() == IntPtrTy) {
Constant *C = CE0->getOperand(0);
Constant *NewOps[] = { C, Constant::getNullValue(C->getType()) };
// FIXME!
return ConstantFoldCompareInstOperands(Predicate, NewOps, 2, TD);
}
}
if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops[1])) {
if (TD && CE0->getOpcode() == CE1->getOpcode()) {
const Type *IntPtrTy = TD->getIntPtrType();
if (CE0->getOpcode() == Instruction::IntToPtr) {
// Convert the integer value to the right size to ensure we get the
// proper extension or truncation.
Constant *C0 = ConstantExpr::getIntegerCast(CE0->getOperand(0),
IntPtrTy, false);
Constant *C1 = ConstantExpr::getIntegerCast(CE1->getOperand(0),
IntPtrTy, false);
Constant *NewOps[] = { C0, C1 };
return ConstantFoldCompareInstOperands(Predicate, NewOps, 2, TD);
}
// Only do this transformation if the int is intptrty in size, otherwise
// there is a truncation or extension that we aren't modeling.
if ((CE0->getOpcode() == Instruction::PtrToInt &&
CE0->getType() == IntPtrTy &&
CE0->getOperand(0)->getType() == CE1->getOperand(0)->getType())) {
Constant *NewOps[] = {
CE0->getOperand(0), CE1->getOperand(0)
};
return ConstantFoldCompareInstOperands(Predicate, NewOps, 2, TD);
}
}
}
}
return ConstantExpr::getCompare(Predicate, Ops[0], Ops[1]);
}
/// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a
/// getelementptr constantexpr, return the constant value being addressed by the
/// constant expression, or null if something is funny and we can't decide.
Constant *llvm::ConstantFoldLoadThroughGEPConstantExpr(Constant *C,
ConstantExpr *CE) {
if (CE->getOperand(1) != Constant::getNullValue(CE->getOperand(1)->getType()))
return 0; // Do not allow stepping over the value!
// Loop over all of the operands, tracking down which value we are
// addressing...
gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
for (++I; I != E; ++I)
if (const StructType *STy = dyn_cast<StructType>(*I)) {
ConstantInt *CU = cast<ConstantInt>(I.getOperand());
assert(CU->getZExtValue() < STy->getNumElements() &&
"Struct index out of range!");
unsigned El = (unsigned)CU->getZExtValue();
if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
C = CS->getOperand(El);
} else if (isa<ConstantAggregateZero>(C)) {
C = Constant::getNullValue(STy->getElementType(El));
} else if (isa<UndefValue>(C)) {
C = UndefValue::get(STy->getElementType(El));
} else {
return 0;
}
} else if (ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand())) {
if (const ArrayType *ATy = dyn_cast<ArrayType>(*I)) {
if (CI->getZExtValue() >= ATy->getNumElements())
return 0;
if (ConstantArray *CA = dyn_cast<ConstantArray>(C))
C = CA->getOperand(CI->getZExtValue());
else if (isa<ConstantAggregateZero>(C))
C = Constant::getNullValue(ATy->getElementType());
else if (isa<UndefValue>(C))
C = UndefValue::get(ATy->getElementType());
else
return 0;
} else if (const VectorType *PTy = dyn_cast<VectorType>(*I)) {
if (CI->getZExtValue() >= PTy->getNumElements())
return 0;
if (ConstantVector *CP = dyn_cast<ConstantVector>(C))
C = CP->getOperand(CI->getZExtValue());
else if (isa<ConstantAggregateZero>(C))
C = Constant::getNullValue(PTy->getElementType());
else if (isa<UndefValue>(C))
C = UndefValue::get(PTy->getElementType());
else
return 0;
} else {
return 0;
}
} else {
return 0;
}
return C;
}
//===----------------------------------------------------------------------===//
// Constant Folding for Calls
//
/// canConstantFoldCallTo - Return true if its even possible to fold a call to
/// the specified function.
bool
llvm::canConstantFoldCallTo(const Function *F) {
switch (F->getIntrinsicID()) {
case Intrinsic::sqrt:
case Intrinsic::powi:
case Intrinsic::bswap:
case Intrinsic::ctpop:
case Intrinsic::ctlz:
case Intrinsic::cttz:
return true;
default: break;
}
const ValueName *NameVal = F->getValueName();
if (NameVal == 0) return false;
const char *Str = NameVal->getKeyData();
unsigned Len = NameVal->getKeyLength();
// In these cases, the check of the length is required. We don't want to
// return true for a name like "cos\0blah" which strcmp would return equal to
// "cos", but has length 8.
switch (Str[0]) {
default: return false;
case 'a':
if (Len == 4)
return !strcmp(Str, "acos") || !strcmp(Str, "asin") ||
!strcmp(Str, "atan");
else if (Len == 5)
return !strcmp(Str, "atan2");
return false;
case 'c':
if (Len == 3)
return !strcmp(Str, "cos");
else if (Len == 4)
return !strcmp(Str, "ceil") || !strcmp(Str, "cosf") ||
!strcmp(Str, "cosh");
return false;
case 'e':
if (Len == 3)
return !strcmp(Str, "exp");
return false;
case 'f':
if (Len == 4)
return !strcmp(Str, "fabs") || !strcmp(Str, "fmod");
else if (Len == 5)
return !strcmp(Str, "floor");
return false;
break;
case 'l':
if (Len == 3 && !strcmp(Str, "log"))
return true;
if (Len == 5 && !strcmp(Str, "log10"))
return true;
return false;
case 'p':
if (Len == 3 && !strcmp(Str, "pow"))
return true;
return false;
case 's':
if (Len == 3)
return !strcmp(Str, "sin");
if (Len == 4)
return !strcmp(Str, "sinh") || !strcmp(Str, "sqrt") ||
!strcmp(Str, "sinf");
if (Len == 5)
return !strcmp(Str, "sqrtf");
return false;
case 't':
if (Len == 3 && !strcmp(Str, "tan"))
return true;
else if (Len == 4 && !strcmp(Str, "tanh"))
return true;
return false;
}
}
static Constant *ConstantFoldFP(double (*NativeFP)(double), double V,
const Type *Ty) {
errno = 0;
V = NativeFP(V);
if (errno != 0) {
errno = 0;
return 0;
}
if (Ty == Type::FloatTy)
return ConstantFP::get(APFloat((float)V));
if (Ty == Type::DoubleTy)
return ConstantFP::get(APFloat(V));
assert(0 && "Can only constant fold float/double");
return 0; // dummy return to suppress warning
}
static Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double),
double V, double W,
const Type *Ty) {
errno = 0;
V = NativeFP(V, W);
if (errno != 0) {
errno = 0;
return 0;
}
if (Ty == Type::FloatTy)
return ConstantFP::get(APFloat((float)V));
if (Ty == Type::DoubleTy)
return ConstantFP::get(APFloat(V));
assert(0 && "Can only constant fold float/double");
return 0; // dummy return to suppress warning
}
/// ConstantFoldCall - Attempt to constant fold a call to the specified function
/// with the specified arguments, returning null if unsuccessful.
Constant *
llvm::ConstantFoldCall(Function *F,
Constant* const* Operands, unsigned NumOperands) {
const ValueName *NameVal = F->getValueName();
if (NameVal == 0) return 0;
const char *Str = NameVal->getKeyData();
unsigned Len = NameVal->getKeyLength();
const Type *Ty = F->getReturnType();
if (NumOperands == 1) {
if (ConstantFP *Op = dyn_cast<ConstantFP>(Operands[0])) {
if (Ty!=Type::FloatTy && Ty!=Type::DoubleTy)
return 0;
/// Currently APFloat versions of these functions do not exist, so we use
/// the host native double versions. Float versions are not called
/// directly but for all these it is true (float)(f((double)arg)) ==
/// f(arg). Long double not supported yet.
double V = Ty==Type::FloatTy ? (double)Op->getValueAPF().convertToFloat():
Op->getValueAPF().convertToDouble();
switch (Str[0]) {
case 'a':
if (Len == 4 && !strcmp(Str, "acos"))
return ConstantFoldFP(acos, V, Ty);
else if (Len == 4 && !strcmp(Str, "asin"))
return ConstantFoldFP(asin, V, Ty);
else if (Len == 4 && !strcmp(Str, "atan"))
return ConstantFoldFP(atan, V, Ty);
break;
case 'c':
if (Len == 4 && !strcmp(Str, "ceil"))
return ConstantFoldFP(ceil, V, Ty);
else if (Len == 3 && !strcmp(Str, "cos"))
return ConstantFoldFP(cos, V, Ty);
else if (Len == 4 && !strcmp(Str, "cosh"))
return ConstantFoldFP(cosh, V, Ty);
else if (Len == 4 && !strcmp(Str, "cosf"))
return ConstantFoldFP(cos, V, Ty);
break;
case 'e':
if (Len == 3 && !strcmp(Str, "exp"))
return ConstantFoldFP(exp, V, Ty);
break;
case 'f':
if (Len == 4 && !strcmp(Str, "fabs"))
return ConstantFoldFP(fabs, V, Ty);
else if (Len == 5 && !strcmp(Str, "floor"))
return ConstantFoldFP(floor, V, Ty);
break;
case 'l':
if (Len == 3 && !strcmp(Str, "log") && V > 0)
return ConstantFoldFP(log, V, Ty);
else if (Len == 5 && !strcmp(Str, "log10") && V > 0)
return ConstantFoldFP(log10, V, Ty);
else if (!strcmp(Str, "llvm.sqrt.f32") ||
!strcmp(Str, "llvm.sqrt.f64")) {
if (V >= -0.0)
return ConstantFoldFP(sqrt, V, Ty);
else // Undefined
return Constant::getNullValue(Ty);
}
break;
case 's':
if (Len == 3 && !strcmp(Str, "sin"))
return ConstantFoldFP(sin, V, Ty);
else if (Len == 4 && !strcmp(Str, "sinh"))
return ConstantFoldFP(sinh, V, Ty);
else if (Len == 4 && !strcmp(Str, "sqrt") && V >= 0)
return ConstantFoldFP(sqrt, V, Ty);
else if (Len == 5 && !strcmp(Str, "sqrtf") && V >= 0)
return ConstantFoldFP(sqrt, V, Ty);
else if (Len == 4 && !strcmp(Str, "sinf"))
return ConstantFoldFP(sin, V, Ty);
break;
case 't':
if (Len == 3 && !strcmp(Str, "tan"))
return ConstantFoldFP(tan, V, Ty);
else if (Len == 4 && !strcmp(Str, "tanh"))
return ConstantFoldFP(tanh, V, Ty);
break;
default:
break;
}
} else if (ConstantInt *Op = dyn_cast<ConstantInt>(Operands[0])) {
if (Len > 11 && !memcmp(Str, "llvm.bswap", 10))
return ConstantInt::get(Op->getValue().byteSwap());
else if (Len > 11 && !memcmp(Str, "llvm.ctpop", 10))
return ConstantInt::get(Ty, Op->getValue().countPopulation());
else if (Len > 10 && !memcmp(Str, "llvm.cttz", 9))
return ConstantInt::get(Ty, Op->getValue().countTrailingZeros());
else if (Len > 10 && !memcmp(Str, "llvm.ctlz", 9))
return ConstantInt::get(Ty, Op->getValue().countLeadingZeros());
}
} else if (NumOperands == 2) {
if (ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0])) {
if (Ty!=Type::FloatTy && Ty!=Type::DoubleTy)
return 0;
double Op1V = Ty==Type::FloatTy ?
(double)Op1->getValueAPF().convertToFloat():
Op1->getValueAPF().convertToDouble();
if (ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) {
double Op2V = Ty==Type::FloatTy ?
(double)Op2->getValueAPF().convertToFloat():
Op2->getValueAPF().convertToDouble();
if (Len == 3 && !strcmp(Str, "pow")) {
return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty);
} else if (Len == 4 && !strcmp(Str, "fmod")) {
return ConstantFoldBinaryFP(fmod, Op1V, Op2V, Ty);
} else if (Len == 5 && !strcmp(Str, "atan2")) {
return ConstantFoldBinaryFP(atan2, Op1V, Op2V, Ty);
}
} else if (ConstantInt *Op2C = dyn_cast<ConstantInt>(Operands[1])) {
if (!strcmp(Str, "llvm.powi.f32")) {
return ConstantFP::get(APFloat((float)std::pow((float)Op1V,
(int)Op2C->getZExtValue())));
} else if (!strcmp(Str, "llvm.powi.f64")) {
return ConstantFP::get(APFloat((double)std::pow((double)Op1V,
(int)Op2C->getZExtValue())));
}
}
}
}
return 0;
}
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