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Diffstat (limited to 'contrib/llvm/lib/Bitcode/Reader/ValueList.cpp')
| -rw-r--r-- | contrib/llvm/lib/Bitcode/Reader/ValueList.cpp | 199 |
1 files changed, 199 insertions, 0 deletions
diff --git a/contrib/llvm/lib/Bitcode/Reader/ValueList.cpp b/contrib/llvm/lib/Bitcode/Reader/ValueList.cpp new file mode 100644 index 000000000000..7152a51cea6e --- /dev/null +++ b/contrib/llvm/lib/Bitcode/Reader/ValueList.cpp @@ -0,0 +1,199 @@ +//===----- ValueList.cpp - Internal BitcodeReader implementation ----------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// + +#include "ValueList.h" +#include "llvm/IR/Constants.h" +#include "llvm/IR/Instructions.h" + +using namespace llvm; + +namespace llvm { +namespace { + +/// \brief A class for maintaining the slot number definition +/// as a placeholder for the actual definition for forward constants defs. +class ConstantPlaceHolder : public ConstantExpr { + void operator=(const ConstantPlaceHolder &) = delete; + +public: + // allocate space for exactly one operand + void *operator new(size_t s) { return User::operator new(s, 1); } + explicit ConstantPlaceHolder(Type *Ty, LLVMContext &Context) + : ConstantExpr(Ty, Instruction::UserOp1, &Op<0>(), 1) { + Op<0>() = UndefValue::get(Type::getInt32Ty(Context)); + } + + /// \brief Methods to support type inquiry through isa, cast, and dyn_cast. + static bool classof(const Value *V) { + return isa<ConstantExpr>(V) && + cast<ConstantExpr>(V)->getOpcode() == Instruction::UserOp1; + } + + /// Provide fast operand accessors + DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value); +}; + +} // end anonymous namespace + +// FIXME: can we inherit this from ConstantExpr? +template <> +struct OperandTraits<ConstantPlaceHolder> + : public FixedNumOperandTraits<ConstantPlaceHolder, 1> {}; +DEFINE_TRANSPARENT_OPERAND_ACCESSORS(ConstantPlaceHolder, Value) + +} // end namespace llvm + +void BitcodeReaderValueList::assignValue(Value *V, unsigned Idx) { + if (Idx == size()) { + push_back(V); + return; + } + + if (Idx >= size()) + resize(Idx + 1); + + WeakVH &OldV = ValuePtrs[Idx]; + if (!OldV) { + OldV = V; + return; + } + + // Handle constants and non-constants (e.g. instrs) differently for + // efficiency. + if (Constant *PHC = dyn_cast<Constant>(&*OldV)) { + ResolveConstants.push_back(std::make_pair(PHC, Idx)); + OldV = V; + } else { + // If there was a forward reference to this value, replace it. + Value *PrevVal = OldV; + OldV->replaceAllUsesWith(V); + delete PrevVal; + } +} + +Constant *BitcodeReaderValueList::getConstantFwdRef(unsigned Idx, Type *Ty) { + if (Idx >= size()) + resize(Idx + 1); + + if (Value *V = ValuePtrs[Idx]) { + if (Ty != V->getType()) + report_fatal_error("Type mismatch in constant table!"); + return cast<Constant>(V); + } + + // Create and return a placeholder, which will later be RAUW'd. + Constant *C = new ConstantPlaceHolder(Ty, Context); + ValuePtrs[Idx] = C; + return C; +} + +Value *BitcodeReaderValueList::getValueFwdRef(unsigned Idx, Type *Ty) { + // Bail out for a clearly invalid value. This would make us call resize(0) + if (Idx == std::numeric_limits<unsigned>::max()) + return nullptr; + + if (Idx >= size()) + resize(Idx + 1); + + if (Value *V = ValuePtrs[Idx]) { + // If the types don't match, it's invalid. + if (Ty && Ty != V->getType()) + return nullptr; + return V; + } + + // No type specified, must be invalid reference. + if (!Ty) + return nullptr; + + // Create and return a placeholder, which will later be RAUW'd. + Value *V = new Argument(Ty); + ValuePtrs[Idx] = V; + return V; +} + +/// Once all constants are read, this method bulk resolves any forward +/// references. The idea behind this is that we sometimes get constants (such +/// as large arrays) which reference *many* forward ref constants. Replacing +/// each of these causes a lot of thrashing when building/reuniquing the +/// constant. Instead of doing this, we look at all the uses and rewrite all +/// the place holders at once for any constant that uses a placeholder. +void BitcodeReaderValueList::resolveConstantForwardRefs() { + // Sort the values by-pointer so that they are efficient to look up with a + // binary search. + std::sort(ResolveConstants.begin(), ResolveConstants.end()); + + SmallVector<Constant *, 64> NewOps; + + while (!ResolveConstants.empty()) { + Value *RealVal = operator[](ResolveConstants.back().second); + Constant *Placeholder = ResolveConstants.back().first; + ResolveConstants.pop_back(); + + // Loop over all users of the placeholder, updating them to reference the + // new value. If they reference more than one placeholder, update them all + // at once. + while (!Placeholder->use_empty()) { + auto UI = Placeholder->user_begin(); + User *U = *UI; + + // If the using object isn't uniqued, just update the operands. This + // handles instructions and initializers for global variables. + if (!isa<Constant>(U) || isa<GlobalValue>(U)) { + UI.getUse().set(RealVal); + continue; + } + + // Otherwise, we have a constant that uses the placeholder. Replace that + // constant with a new constant that has *all* placeholder uses updated. + Constant *UserC = cast<Constant>(U); + for (User::op_iterator I = UserC->op_begin(), E = UserC->op_end(); I != E; + ++I) { + Value *NewOp; + if (!isa<ConstantPlaceHolder>(*I)) { + // Not a placeholder reference. + NewOp = *I; + } else if (*I == Placeholder) { + // Common case is that it just references this one placeholder. + NewOp = RealVal; + } else { + // Otherwise, look up the placeholder in ResolveConstants. + ResolveConstantsTy::iterator It = std::lower_bound( + ResolveConstants.begin(), ResolveConstants.end(), + std::pair<Constant *, unsigned>(cast<Constant>(*I), 0)); + assert(It != ResolveConstants.end() && It->first == *I); + NewOp = operator[](It->second); + } + + NewOps.push_back(cast<Constant>(NewOp)); + } + + // Make the new constant. + Constant *NewC; + if (ConstantArray *UserCA = dyn_cast<ConstantArray>(UserC)) { + NewC = ConstantArray::get(UserCA->getType(), NewOps); + } else if (ConstantStruct *UserCS = dyn_cast<ConstantStruct>(UserC)) { + NewC = ConstantStruct::get(UserCS->getType(), NewOps); + } else if (isa<ConstantVector>(UserC)) { + NewC = ConstantVector::get(NewOps); + } else { + assert(isa<ConstantExpr>(UserC) && "Must be a ConstantExpr."); + NewC = cast<ConstantExpr>(UserC)->getWithOperands(NewOps); + } + + UserC->replaceAllUsesWith(NewC); + UserC->destroyConstant(); + NewOps.clear(); + } + + // Update all ValueHandles, they should be the only users at this point. + Placeholder->replaceAllUsesWith(RealVal); + delete Placeholder; + } +} |