#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/Target/TargetData.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Support/MathExtras.h"
#include <cerrno>
using namespace llvm;
//===----------------------------------------------------------------------===//
-// Constant Folding ...
-//
+// 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 (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i, ++GTI) {
+ ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(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.getTypeSize(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** Ops, unsigned NumOps,
+ const Type *ResultTy,
+ const TargetData *TD) {
+ Constant *Ptr = Ops[0];
+ if (!cast<PointerType>(Ptr->getType())->getElementType()->isSized())
+ return 0;
+
+ if (TD && Ptr->isNullValue()) {
+ // 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'
+ bool isFoldableGEP = true;
+ for (unsigned i = 1; i != NumOps; ++i)
+ if (!isa<ConstantInt>(Ops[i])) {
+ isFoldableGEP = false;
+ break;
+ }
+ if (isFoldableGEP) {
+ uint64_t Offset = TD->getIndexedOffset(Ptr->getType(),
+ (Value**)Ops+1, NumOps-1);
+ Constant *C = ConstantInt::get(TD->getIntPtrType(), Offset);
+ return ConstantExpr::getIntToPtr(C, ResultTy);
+ }
+ }
+
+ 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 (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
+ if (Constant *Op = dyn_cast<Constant>(I->getOperand(i)))
+ Ops.push_back(Op);
+ else
+ return 0; // All operands not constant!
+
+ return ConstantFoldInstOperands(I, &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(const Instruction* I,
+ Constant** Ops, unsigned NumOps,
+ const TargetData *TD) {
+ unsigned Opc = I->getOpcode();
+ const Type *DestTy = I->getType();
+
+ // Handle easy binops first.
+ if (isa<BinaryOperator>(I)) {
+ if (isa<ConstantExpr>(Ops[0]) || isa<ConstantExpr>(Ops[1]))
+ if (Constant *C = SymbolicallyEvaluateBinop(I->getOpcode(), Ops[0],
+ Ops[1], TD))
+ return C;
+
+ return ConstantExpr::get(Opc, Ops[0], Ops[1]);
+ }
+
+ switch (Opc) {
+ 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:
+ return ConstantExpr::getCompare(cast<CmpInst>(I)->getPredicate(), Ops[0],
+ Ops[1]);
+ 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:
+ case Instruction::PtrToInt:
+ case Instruction::IntToPtr:
+ case Instruction::BitCast:
+ return ConstantExpr::getCast(Opc, 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, I->getType(), TD))
+ return C;
+
+ return ConstantExpr::getGetElementPtr(Ops[0], Ops+1, NumOps-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.
switch (F->getIntrinsicID()) {
case Intrinsic::sqrt_f32:
case Intrinsic::sqrt_f64:
- case Intrinsic::bswap_i16:
- case Intrinsic::bswap_i32:
- case Intrinsic::bswap_i64:
- // FIXME: these should be constant folded as well
- //case Intrinsic::ctpop_i8:
- //case Intrinsic::ctpop_i16:
- //case Intrinsic::ctpop_i32:
- //case Intrinsic::ctpop_i64:
- //case Intrinsic::ctlz_i8:
- //case Intrinsic::ctlz_i16:
- //case Intrinsic::ctlz_i32:
- //case Intrinsic::ctlz_i64:
- //case Intrinsic::cttz_i8:
- //case Intrinsic::cttz_i16:
- //case Intrinsic::cttz_i32:
- //case Intrinsic::cttz_i64:
+ case Intrinsic::powi_f32:
+ case Intrinsic::powi_f64:
+ case Intrinsic::bswap:
+ case Intrinsic::ctpop:
+ case Intrinsic::ctlz:
+ case Intrinsic::cttz:
return true;
default: break;
}
}
}
-Constant *
-llvm::ConstantFoldFP(double (*NativeFP)(double), double V, const Type *Ty) {
+static Constant *ConstantFoldFP(double (*NativeFP)(double), double V,
+ const Type *Ty) {
errno = 0;
V = NativeFP(V);
if (errno == 0)
return ConstantFP::get(Ty, V);
+ errno = 0;
+ return 0;
+}
+
+static Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double),
+ double V, double W,
+ const Type *Ty) {
+ errno = 0;
+ V = NativeFP(V, W);
+ if (errno == 0)
+ return ConstantFP::get(Ty, V);
+ errno = 0;
return 0;
}
/// ConstantFoldCall - Attempt to constant fold a call to the specified function
/// with the specified arguments, returning null if unsuccessful.
Constant *
-llvm::ConstantFoldCall(Function *F, const std::vector<Constant*> &Operands) {
+llvm::ConstantFoldCall(Function *F, Constant** Operands, unsigned NumOperands) {
const std::string &Name = F->getName();
const Type *Ty = F->getReturnType();
- if (Operands.size() == 1) {
+ if (NumOperands == 1) {
if (ConstantFP *Op = dyn_cast<ConstantFP>(Operands[0])) {
double V = Op->getValue();
switch (Name[0])
else if (Name == "asin")
return ConstantFoldFP(asin, V, Ty);
else if (Name == "atan")
- return ConstantFP::get(Ty, atan(V));
+ return ConstantFoldFP(atan, V, Ty);
break;
case 'c':
if (Name == "ceil")
return ConstantFoldFP(ceil, V, Ty);
else if (Name == "cos")
- return ConstantFP::get(Ty, cos(V));
+ return ConstantFoldFP(cos, V, Ty);
else if (Name == "cosh")
- return ConstantFP::get(Ty, cosh(V));
+ return ConstantFoldFP(cosh, V, Ty);
break;
case 'e':
if (Name == "exp")
- return ConstantFP::get(Ty, exp(V));
+ return ConstantFoldFP(exp, V, Ty);
break;
case 'f':
if (Name == "fabs")
break;
case 'l':
if (Name == "log" && V > 0)
- return ConstantFP::get(Ty, log(V));
+ return ConstantFoldFP(log, V, Ty);
else if (Name == "log10" && V > 0)
return ConstantFoldFP(log10, V, Ty);
else if (Name == "llvm.sqrt.f32" || Name == "llvm.sqrt.f64") {
break;
case 's':
if (Name == "sin")
- return ConstantFP::get(Ty, sin(V));
+ return ConstantFoldFP(sin, V, Ty);
else if (Name == "sinh")
- return ConstantFP::get(Ty, sinh(V));
+ return ConstantFoldFP(sinh, V, Ty);
else if (Name == "sqrt" && V >= 0)
- return ConstantFP::get(Ty, sqrt(V));
+ return ConstantFoldFP(sqrt, V, Ty);
else if (Name == "sqrtf" && V >= 0)
- return ConstantFP::get(Ty, sqrt((float)V));
+ return ConstantFoldFP(sqrt, V, Ty);
break;
case 't':
if (Name == "tan")
- return ConstantFP::get(Ty, tan(V));
+ return ConstantFoldFP(tan, V, Ty);
else if (Name == "tanh")
- return ConstantFP::get(Ty, tanh(V));
+ return ConstantFoldFP(tanh, V, Ty);
break;
default:
break;
}
} else if (ConstantInt *Op = dyn_cast<ConstantInt>(Operands[0])) {
- uint64_t V = Op->getZExtValue();
- if (Name == "llvm.bswap.i16")
- return ConstantInt::get(Ty, ByteSwap_16(V));
- else if (Name == "llvm.bswap.i32")
- return ConstantInt::get(Ty, ByteSwap_32(V));
- else if (Name == "llvm.bswap.i64")
- return ConstantInt::get(Ty, ByteSwap_64(V));
+ if (Name.size() > 11 && !memcmp(&Name[0], "llvm.bswap", 10)) {
+ return ConstantInt::get(Op->getValue().byteSwap());
+ } else if (Name.size() > 11 && !memcmp(&Name[0],"llvm.ctpop",10)) {
+ uint64_t ctpop = Op->getValue().countPopulation();
+ return ConstantInt::get(Type::Int32Ty, ctpop);
+ } else if (Name.size() > 10 && !memcmp(&Name[0], "llvm.cttz", 9)) {
+ uint64_t cttz = Op->getValue().countTrailingZeros();
+ return ConstantInt::get(Type::Int32Ty, cttz);
+ } else if (Name.size() > 10 && !memcmp(&Name[0], "llvm.ctlz", 9)) {
+ uint64_t ctlz = Op->getValue().countLeadingZeros();
+ return ConstantInt::get(Type::Int32Ty, ctlz);
+ }
}
- } else if (Operands.size() == 2) {
+ } else if (NumOperands == 2) {
if (ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0])) {
double Op1V = Op1->getValue();
if (ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) {
double Op2V = Op2->getValue();
if (Name == "pow") {
- errno = 0;
- double V = pow(Op1V, Op2V);
- if (errno == 0)
- return ConstantFP::get(Ty, V);
+ return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty);
} else if (Name == "fmod") {
- errno = 0;
- double V = fmod(Op1V, Op2V);
- if (errno == 0)
- return ConstantFP::get(Ty, V);
- } else if (Name == "atan2")
- return ConstantFP::get(Ty, atan2(Op1V,Op2V));
+ return ConstantFoldBinaryFP(fmod, Op1V, Op2V, Ty);
+ } else if (Name == "atan2") {
+ return ConstantFoldBinaryFP(atan2, Op1V, Op2V, Ty);
+ }
+ } else if (ConstantInt *Op2C = dyn_cast<ConstantInt>(Operands[1])) {
+ if (Name == "llvm.powi.f32") {
+ return ConstantFP::get(Ty, std::pow((float)Op1V,
+ (int)Op2C->getZExtValue()));
+ } else if (Name == "llvm.powi.f64") {
+ return ConstantFP::get(Ty, std::pow((double)Op1V,
+ (int)Op2C->getZExtValue()));
+ }
}
}
}
projects / oota-llvm.git / blobdiff