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//===-- Local.h - Functions to perform local transformations ----*- C++ -*-===//
// 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 perform various local transformations to the
// program.
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/GetElementPtrTypeIterator.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Operator.h"
namespace llvm {
class User;
class BasicBlock;
class Function;
class BranchInst;
class Instruction;
class DbgDeclareInst;
class StoreInst;
class LoadInst;
class Value;
class Pass;
class PHINode;
class AllocaInst;
class ConstantExpr;
class DataLayout;
class TargetLibraryInfo;
class TargetTransformInfo;
class DIBuilder;
class AliasAnalysis;
template<typename T> class SmallVectorImpl;
// Local constant propagation.
/// ConstantFoldTerminator - If a terminator instruction is predicated on a
/// constant value, convert it into an unconditional branch to the constant
/// destination. This is a nontrivial operation because the successors of this
/// basic block must have their PHI nodes updated.
/// Also calls RecursivelyDeleteTriviallyDeadInstructions() on any branch/switch
/// conditions and indirectbr addresses this might make dead if
/// DeleteDeadConditions is true.
bool ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions = false,
const TargetLibraryInfo *TLI = nullptr);
// Local dead code elimination.
/// isInstructionTriviallyDead - Return true if the result produced by the
/// instruction is not used, and the instruction has no side effects.
bool isInstructionTriviallyDead(Instruction *I,
const TargetLibraryInfo *TLI = nullptr);
/// RecursivelyDeleteTriviallyDeadInstructions - If the specified value is a
/// trivially dead instruction, delete it. If that makes any of its operands
/// trivially dead, delete them too, recursively. Return true if any
/// instructions were deleted.
bool RecursivelyDeleteTriviallyDeadInstructions(Value *V,
const TargetLibraryInfo *TLI = nullptr);
/// RecursivelyDeleteDeadPHINode - If the specified value is an effectively
/// dead PHI node, due to being a def-use chain of single-use nodes that
/// either forms a cycle or is terminated by a trivially dead instruction,
/// delete it. If that makes any of its operands trivially dead, delete them
/// too, recursively. Return true if a change was made.
bool RecursivelyDeleteDeadPHINode(PHINode *PN,
const TargetLibraryInfo *TLI = nullptr);
/// SimplifyInstructionsInBlock - Scan the specified basic block and try to
/// simplify any instructions in it and recursively delete dead instructions.
/// This returns true if it changed the code, note that it can delete
/// instructions in other blocks as well in this block.
bool SimplifyInstructionsInBlock(BasicBlock *BB, const DataLayout *TD = nullptr,
const TargetLibraryInfo *TLI = nullptr);
// Control Flow Graph Restructuring.
/// RemovePredecessorAndSimplify - Like BasicBlock::removePredecessor, this
/// method is called when we're about to delete Pred as a predecessor of BB. If
/// BB contains any PHI nodes, this drops the entries in the PHI nodes for Pred.
/// Unlike the removePredecessor method, this attempts to simplify uses of PHI
/// nodes that collapse into identity values. For example, if we have:
/// x = phi(1, 0, 0, 0)
/// y = and x, z
/// .. and delete the predecessor corresponding to the '1', this will attempt to
/// recursively fold the 'and' to 0.
void RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred,
DataLayout *TD = nullptr);
/// MergeBasicBlockIntoOnlyPred - BB is a block with one predecessor and its
/// predecessor is known to have one successor (BB!). Eliminate the edge
/// between them, moving the instructions in the predecessor into BB. This
/// deletes the predecessor block.
void MergeBasicBlockIntoOnlyPred(BasicBlock *BB, Pass *P = nullptr);
/// TryToSimplifyUncondBranchFromEmptyBlock - BB is known to contain an
/// unconditional branch, and contains no instructions other than PHI nodes,
/// potential debug intrinsics and the branch. If possible, eliminate BB by
/// rewriting all the predecessors to branch to the successor block and return
/// true. If we can't transform, return false.
bool TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB);
/// EliminateDuplicatePHINodes - Check for and eliminate duplicate PHI
/// nodes in this block. This doesn't try to be clever about PHI nodes
/// which differ only in the order of the incoming values, but instcombine
/// orders them so it usually won't matter.
bool EliminateDuplicatePHINodes(BasicBlock *BB);
/// SimplifyCFG - This function is used to do simplification of a CFG. For
/// example, it adjusts branches to branches to eliminate the extra hop, it
/// eliminates unreachable basic blocks, and does other "peephole" optimization
/// of the CFG. It returns true if a modification was made, possibly deleting
/// the basic block that was pointed to.
bool SimplifyCFG(BasicBlock *BB, const TargetTransformInfo &TTI,
const DataLayout *TD = nullptr);
/// FlatternCFG - This function is used to flatten a CFG. For
/// example, it uses parallel-and and parallel-or mode to collapse
// if-conditions and merge if-regions with identical statements.
bool FlattenCFG(BasicBlock *BB, AliasAnalysis *AA = nullptr);
/// FoldBranchToCommonDest - If this basic block is ONLY a setcc and a branch,
/// and if a predecessor branches to us and one of our successors, fold the
/// setcc into the predecessor and use logical operations to pick the right
/// destination.
bool FoldBranchToCommonDest(BranchInst *BI, const DataLayout *DL = nullptr);
/// DemoteRegToStack - This function takes a virtual register computed by an
/// Instruction and replaces it with a slot in the stack frame, allocated via
/// alloca. This allows the CFG to be changed around without fear of
/// invalidating the SSA information for the value. It returns the pointer to
/// the alloca inserted to create a stack slot for X.
AllocaInst *DemoteRegToStack(Instruction &X,
bool VolatileLoads = false,
Instruction *AllocaPoint = nullptr);
/// DemotePHIToStack - This function takes a virtual register computed by a phi
/// node and replaces it with a slot in the stack frame, allocated via alloca.
/// The phi node is deleted and it returns the pointer to the alloca inserted.
AllocaInst *DemotePHIToStack(PHINode *P, Instruction *AllocaPoint = nullptr);
/// getOrEnforceKnownAlignment - If the specified pointer has an alignment that
/// we can determine, return it, otherwise return 0. If PrefAlign is specified,
/// and it is more than the alignment of the ultimate object, see if we can
/// increase the alignment of the ultimate object, making this check succeed.
unsigned getOrEnforceKnownAlignment(Value *V, unsigned PrefAlign,
const DataLayout *TD = nullptr);
/// getKnownAlignment - Try to infer an alignment for the specified pointer.
static inline unsigned getKnownAlignment(Value *V,
const DataLayout *TD = nullptr) {
return getOrEnforceKnownAlignment(V, 0, TD);
/// EmitGEPOffset - Given a getelementptr instruction/constantexpr, emit the
/// code necessary to compute the offset from the base pointer (without adding
/// in the base pointer). Return the result as a signed integer of intptr size.
/// When NoAssumptions is true, no assumptions about index computation not
/// overflowing is made.
template<typename IRBuilderTy>
Value *EmitGEPOffset(IRBuilderTy *Builder, const DataLayout &TD, User *GEP,
bool NoAssumptions = false) {
GEPOperator *GEPOp = cast<GEPOperator>(GEP);
Type *IntPtrTy = TD.getIntPtrType(GEP->getType());
Value *Result = Constant::getNullValue(IntPtrTy);
// If the GEP is inbounds, we know that none of the addressing operations will
// overflow in an unsigned sense.
bool isInBounds = GEPOp->isInBounds() && !NoAssumptions;
// Build a mask for high order bits.
unsigned IntPtrWidth = IntPtrTy->getScalarType()->getIntegerBitWidth();
uint64_t PtrSizeMask = ~0ULL >> (64 - IntPtrWidth);
gep_type_iterator GTI = gep_type_begin(GEP);
for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end(); i != e;
++i, ++GTI) {
Value *Op = *i;
uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType()) & PtrSizeMask;
if (Constant *OpC = dyn_cast<Constant>(Op)) {
if (OpC->isZeroValue())
// Handle a struct index, which adds its field offset to the pointer.
if (StructType *STy = dyn_cast<StructType>(*GTI)) {
if (OpC->getType()->isVectorTy())
OpC = OpC->getSplatValue();
uint64_t OpValue = cast<ConstantInt>(OpC)->getZExtValue();
Size = TD.getStructLayout(STy)->getElementOffset(OpValue);
if (Size)
Result = Builder->CreateAdd(Result, ConstantInt::get(IntPtrTy, Size),
Constant *Scale = ConstantInt::get(IntPtrTy, Size);
Constant *OC = ConstantExpr::getIntegerCast(OpC, IntPtrTy, true /*SExt*/);
Scale = ConstantExpr::getMul(OC, Scale, isInBounds/*NUW*/);
// Emit an add instruction.
Result = Builder->CreateAdd(Result, Scale, GEP->getName()+".offs");
// Convert to correct type.
if (Op->getType() != IntPtrTy)
Op = Builder->CreateIntCast(Op, IntPtrTy, true, Op->getName()+".c");
if (Size != 1) {
// We'll let instcombine(mul) convert this to a shl if possible.
Op = Builder->CreateMul(Op, ConstantInt::get(IntPtrTy, Size),
GEP->getName()+".idx", isInBounds /*NUW*/);
// Emit an add instruction.
Result = Builder->CreateAdd(Op, Result, GEP->getName()+".offs");
return Result;
/// Dbg Intrinsic utilities
/// Inserts a llvm.dbg.value intrinsic before a store to an alloca'd value
/// that has an associated llvm.dbg.decl intrinsic.
bool ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
StoreInst *SI, DIBuilder &Builder);
/// Inserts a llvm.dbg.value intrinsic before a load of an alloca'd value
/// that has an associated llvm.dbg.decl intrinsic.
bool ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
LoadInst *LI, DIBuilder &Builder);
/// LowerDbgDeclare - Lowers llvm.dbg.declare intrinsics into appropriate set
/// of llvm.dbg.value intrinsics.
bool LowerDbgDeclare(Function &F);
/// FindAllocaDbgDeclare - Finds the llvm.dbg.declare intrinsic corresponding to
/// an alloca, if any.
DbgDeclareInst *FindAllocaDbgDeclare(Value *V);
/// replaceDbgDeclareForAlloca - Replaces llvm.dbg.declare instruction when
/// alloca is replaced with a new value.
bool replaceDbgDeclareForAlloca(AllocaInst *AI, Value *NewAllocaAddress,
DIBuilder &Builder);
/// \brief Remove all blocks that can not be reached from the function's entry.
/// Returns true if any basic block was removed.
bool removeUnreachableBlocks(Function &F);
} // End llvm namespace