Import LLVM, at r72732.vendor/llvm/llvm-r72732

1 files changed, 829 insertions, 0 deletions

diff --git a/lib/Analysis/ConstantFolding.cpp b/lib/Analysis/ConstantFolding.cpp
new file mode 100644
index 000000000000..e5ab3226ce49
--- /dev/null
+++ b/lib/Analysis/ConstantFolding.cpp
@@ -0,0 +1,829 @@
+//===-- 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/GlobalVariable.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.getTypeAllocSize(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);
+      }
+  }
+    
+  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.data(), 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 UndefValue::get(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.data(), Ops.size(), TD);
+  else
+    return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
+                                    Ops.data(), 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.data(), Ops.size(), TD);
+  else 
+    return ConstantFoldInstOperands(CE->getOpcode(), CE->getType(),
+                                    Ops.data(), 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:
+  case Instruction::VICmp:
+  case Instruction::VFCmp:
+    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();
+        if (TD->getPointerSizeInBits() < InWidth) {
+          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:
+    // If the input is a ptrtoint, turn the pair into a ptr to ptr bitcast if
+    // the int size is >= the ptr size.  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 &&
+          TD->getPointerSizeInBits() <=
+          CE->getType()->getPrimitiveSizeInBits()) {
+        if (CE->getOpcode() == Instruction::PtrToInt) {
+          Constant *Input = CE->getOperand(0);
+          Constant *C = FoldBitCast(Input, DestTy, *TD);
+          return C ? C : ConstantExpr::getBitCast(Input, DestTy);
+        }
+        // If there's a constant offset added to the integer value before
+        // it is casted back to a pointer, see if the expression can be
+        // converted into a GEP.
+        if (CE->getOpcode() == Instruction::Add)
+          if (ConstantInt *L = dyn_cast<ConstantInt>(CE->getOperand(0)))
+            if (ConstantExpr *R = dyn_cast<ConstantExpr>(CE->getOperand(1)))
+              if (R->getOpcode() == Instruction::PtrToInt)
+                if (GlobalVariable *GV =
+                      dyn_cast<GlobalVariable>(R->getOperand(0))) {
+                  const PointerType *GVTy = cast<PointerType>(GV->getType());
+                  if (const ArrayType *AT =
+                        dyn_cast<ArrayType>(GVTy->getElementType())) {
+                    const Type *ElTy = AT->getElementType();
+                    uint64_t AllocSize = TD->getTypeAllocSize(ElTy);
+                    APInt PSA(L->getValue().getBitWidth(), AllocSize);
+                    if (ElTy == cast<PointerType>(DestTy)->getElementType() &&
+                        L->getValue().urem(PSA) == 0) {
+                      APInt ElemIdx = L->getValue().udiv(PSA);
+                      if (ElemIdx.ult(APInt(ElemIdx.getBitWidth(),
+                                            AT->getNumElements()))) {
+                        Constant *Index[] = {
+                          Constant::getNullValue(CE->getType()),
+                          ConstantInt::get(ElemIdx)
+                        };
+                        return ConstantExpr::getGetElementPtr(GV, &Index[0], 2);
+                      }
+                    }
+                  }
+                }
+      }
+    }
+    return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
+  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;
+  }
+
+  if (!F->hasName()) return false;
+  const char *Str = F->getNameStart();
+  unsigned Len = F->getNameLen();
+  
+  // 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) {
+  if (!F->hasName()) return 0;
+  const char *Str = F->getNameStart();
+  unsigned Len = F->getNameLen();
+  
+  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;
+}
+