1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500
|
//===- 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.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_TRANSFORMS_UTILS_LOCAL_H
#define LLVM_TRANSFORMS_UTILS_LOCAL_H
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/TinyPtrVector.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/GetElementPtrTypeIterator.h"
#include "llvm/IR/Operator.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/User.h"
#include "llvm/IR/Value.h"
#include "llvm/Support/Casting.h"
#include <cstdint>
#include <limits>
namespace llvm {
class AllocaInst;
class AssumptionCache;
class BasicBlock;
class BranchInst;
class CallInst;
class DbgInfoIntrinsic;
class DbgValueInst;
class DIBuilder;
class Function;
class Instruction;
class LazyValueInfo;
class LoadInst;
class MDNode;
class PHINode;
class StoreInst;
class TargetLibraryInfo;
class TargetTransformInfo;
/// A set of parameters used to control the transforms in the SimplifyCFG pass.
/// Options may change depending on the position in the optimization pipeline.
/// For example, canonical form that includes switches and branches may later be
/// replaced by lookup tables and selects.
struct SimplifyCFGOptions {
int BonusInstThreshold;
bool ForwardSwitchCondToPhi;
bool ConvertSwitchToLookupTable;
bool NeedCanonicalLoop;
bool SinkCommonInsts;
AssumptionCache *AC;
SimplifyCFGOptions(unsigned BonusThreshold = 1,
bool ForwardSwitchCond = false,
bool SwitchToLookup = false, bool CanonicalLoops = true,
bool SinkCommon = false,
AssumptionCache *AssumpCache = nullptr)
: BonusInstThreshold(BonusThreshold),
ForwardSwitchCondToPhi(ForwardSwitchCond),
ConvertSwitchToLookupTable(SwitchToLookup),
NeedCanonicalLoop(CanonicalLoops),
SinkCommonInsts(SinkCommon),
AC(AssumpCache) {}
// Support 'builder' pattern to set members by name at construction time.
SimplifyCFGOptions &bonusInstThreshold(int I) {
BonusInstThreshold = I;
return *this;
}
SimplifyCFGOptions &forwardSwitchCondToPhi(bool B) {
ForwardSwitchCondToPhi = B;
return *this;
}
SimplifyCFGOptions &convertSwitchToLookupTable(bool B) {
ConvertSwitchToLookupTable = B;
return *this;
}
SimplifyCFGOptions &needCanonicalLoops(bool B) {
NeedCanonicalLoop = B;
return *this;
}
SimplifyCFGOptions &sinkCommonInsts(bool B) {
SinkCommonInsts = B;
return *this;
}
SimplifyCFGOptions &setAssumptionCache(AssumptionCache *Cache) {
AC = Cache;
return *this;
}
};
//===----------------------------------------------------------------------===//
// Local constant propagation.
//
/// 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,
DeferredDominance *DDT = nullptr);
//===----------------------------------------------------------------------===//
// Local dead code elimination.
//
/// 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);
/// Return true if the result produced by the instruction would have no side
/// effects if it was not used. This is equivalent to checking whether
/// isInstructionTriviallyDead would be true if the use count was 0.
bool wouldInstructionBeTriviallyDead(Instruction *I,
const TargetLibraryInfo *TLI = nullptr);
/// 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);
/// 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);
/// 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 TargetLibraryInfo *TLI = nullptr);
//===----------------------------------------------------------------------===//
// Control Flow Graph Restructuring.
//
/// 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,
DeferredDominance *DDT = nullptr);
/// 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, DominatorTree *DT = nullptr,
DeferredDominance *DDT = nullptr);
/// 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,
DeferredDominance *DDT = nullptr);
/// 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);
/// 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. LoopHeaders is an optional input parameter
/// providing the set of loop headers that SimplifyCFG should not eliminate.
bool simplifyCFG(BasicBlock *BB, const TargetTransformInfo &TTI,
const SimplifyCFGOptions &Options = {},
SmallPtrSetImpl<BasicBlock *> *LoopHeaders = nullptr);
/// 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);
/// 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, unsigned BonusInstThreshold = 1);
/// 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);
/// 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);
/// Try to ensure that the alignment of \p V is at least \p PrefAlign bytes. If
/// the owning object can be modified and has an alignment less than \p
/// PrefAlign, it will be increased and \p PrefAlign returned. If the alignment
/// cannot be increased, the known alignment of the value is returned.
///
/// It is not always possible to modify the alignment of the underlying object,
/// so if alignment is important, a more reliable approach is to simply align
/// all global variables and allocation instructions to their preferred
/// alignment from the beginning.
unsigned getOrEnforceKnownAlignment(Value *V, unsigned PrefAlign,
const DataLayout &DL,
const Instruction *CxtI = nullptr,
AssumptionCache *AC = nullptr,
const DominatorTree *DT = nullptr);
/// Try to infer an alignment for the specified pointer.
inline unsigned getKnownAlignment(Value *V, const DataLayout &DL,
const Instruction *CxtI = nullptr,
AssumptionCache *AC = nullptr,
const DominatorTree *DT = nullptr) {
return getOrEnforceKnownAlignment(V, 0, DL, CxtI, AC, DT);
}
/// 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 &DL, User *GEP,
bool NoAssumptions = false) {
GEPOperator *GEPOp = cast<GEPOperator>(GEP);
Type *IntPtrTy = DL.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 =
std::numeric_limits<uint64_t>::max() >> (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 = DL.getTypeAllocSize(GTI.getIndexedType()) & PtrSizeMask;
if (Constant *OpC = dyn_cast<Constant>(Op)) {
if (OpC->isZeroValue())
continue;
// Handle a struct index, which adds its field offset to the pointer.
if (StructType *STy = GTI.getStructTypeOrNull()) {
if (OpC->getType()->isVectorTy())
OpC = OpC->getSplatValue();
uint64_t OpValue = cast<ConstantInt>(OpC)->getZExtValue();
Size = DL.getStructLayout(STy)->getElementOffset(OpValue);
if (Size)
Result = Builder->CreateAdd(Result, ConstantInt::get(IntPtrTy, Size),
GEP->getName()+".offs");
continue;
}
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");
continue;
}
// 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.declare or llvm.dbg.addr intrinsic.
void ConvertDebugDeclareToDebugValue(DbgInfoIntrinsic *DII,
StoreInst *SI, DIBuilder &Builder);
/// Inserts a llvm.dbg.value intrinsic before a load of an alloca'd value
/// that has an associated llvm.dbg.declare or llvm.dbg.addr intrinsic.
void ConvertDebugDeclareToDebugValue(DbgInfoIntrinsic *DII,
LoadInst *LI, DIBuilder &Builder);
/// Inserts a llvm.dbg.value intrinsic after a phi that has an associated
/// llvm.dbg.declare or llvm.dbg.addr intrinsic.
void ConvertDebugDeclareToDebugValue(DbgInfoIntrinsic *DII,
PHINode *LI, DIBuilder &Builder);
/// Lowers llvm.dbg.declare intrinsics into appropriate set of
/// llvm.dbg.value intrinsics.
bool LowerDbgDeclare(Function &F);
/// Finds all intrinsics declaring local variables as living in the memory that
/// 'V' points to. This may include a mix of dbg.declare and
/// dbg.addr intrinsics.
TinyPtrVector<DbgInfoIntrinsic *> FindDbgAddrUses(Value *V);
/// Finds the llvm.dbg.value intrinsics describing a value.
void findDbgValues(SmallVectorImpl<DbgValueInst *> &DbgValues, Value *V);
/// Replaces llvm.dbg.declare instruction when the address it
/// describes is replaced with a new value. If Deref is true, an
/// additional DW_OP_deref is prepended to the expression. If Offset
/// is non-zero, a constant displacement is added to the expression
/// (between the optional Deref operations). Offset can be negative.
bool replaceDbgDeclare(Value *Address, Value *NewAddress,
Instruction *InsertBefore, DIBuilder &Builder,
bool DerefBefore, int Offset, bool DerefAfter);
/// Replaces llvm.dbg.declare instruction when the alloca it describes
/// is replaced with a new value. If Deref is true, an additional
/// DW_OP_deref is prepended to the expression. If Offset is non-zero,
/// a constant displacement is added to the expression (between the
/// optional Deref operations). Offset can be negative. The new
/// llvm.dbg.declare is inserted immediately before AI.
bool replaceDbgDeclareForAlloca(AllocaInst *AI, Value *NewAllocaAddress,
DIBuilder &Builder, bool DerefBefore,
int Offset, bool DerefAfter);
/// Replaces multiple llvm.dbg.value instructions when the alloca it describes
/// is replaced with a new value. If Offset is non-zero, a constant displacement
/// is added to the expression (after the mandatory Deref). Offset can be
/// negative. New llvm.dbg.value instructions are inserted at the locations of
/// the instructions they replace.
void replaceDbgValueForAlloca(AllocaInst *AI, Value *NewAllocaAddress,
DIBuilder &Builder, int Offset = 0);
/// Assuming the instruction \p I is going to be deleted, attempt to salvage any
/// dbg.value intrinsics referring to \p I by rewriting its effect into a
/// DIExpression.
void salvageDebugInfo(Instruction &I);
/// Remove all instructions from a basic block other than it's terminator
/// and any present EH pad instructions.
unsigned removeAllNonTerminatorAndEHPadInstructions(BasicBlock *BB);
/// Insert an unreachable instruction before the specified
/// instruction, making it and the rest of the code in the block dead.
unsigned changeToUnreachable(Instruction *I, bool UseLLVMTrap,
bool PreserveLCSSA = false,
DeferredDominance *DDT = nullptr);
/// Convert the CallInst to InvokeInst with the specified unwind edge basic
/// block. This also splits the basic block where CI is located, because
/// InvokeInst is a terminator instruction. Returns the newly split basic
/// block.
BasicBlock *changeToInvokeAndSplitBasicBlock(CallInst *CI,
BasicBlock *UnwindEdge);
/// Replace 'BB's terminator with one that does not have an unwind successor
/// block. Rewrites `invoke` to `call`, etc. Updates any PHIs in unwind
/// successor.
///
/// \param BB Block whose terminator will be replaced. Its terminator must
/// have an unwind successor.
void removeUnwindEdge(BasicBlock *BB, DeferredDominance *DDT = nullptr);
/// 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, LazyValueInfo *LVI = nullptr,
DeferredDominance *DDT = nullptr);
/// Combine the metadata of two instructions so that K can replace J
///
/// Metadata not listed as known via KnownIDs is removed
void combineMetadata(Instruction *K, const Instruction *J, ArrayRef<unsigned> KnownIDs);
/// Combine the metadata of two instructions so that K can replace J. This
/// specifically handles the case of CSE-like transformations.
///
/// Unknown metadata is removed.
void combineMetadataForCSE(Instruction *K, const Instruction *J);
// Replace each use of 'From' with 'To', if that use does not belong to basic
// block where 'From' is defined. Returns the number of replacements made.
unsigned replaceNonLocalUsesWith(Instruction *From, Value *To);
/// Replace each use of 'From' with 'To' if that use is dominated by
/// the given edge. Returns the number of replacements made.
unsigned replaceDominatedUsesWith(Value *From, Value *To, DominatorTree &DT,
const BasicBlockEdge &Edge);
/// Replace each use of 'From' with 'To' if that use is dominated by
/// the end of the given BasicBlock. Returns the number of replacements made.
unsigned replaceDominatedUsesWith(Value *From, Value *To, DominatorTree &DT,
const BasicBlock *BB);
/// Return true if the CallSite CS calls a gc leaf function.
///
/// A leaf function is a function that does not safepoint the thread during its
/// execution. During a call or invoke to such a function, the callers stack
/// does not have to be made parseable.
///
/// Most passes can and should ignore this information, and it is only used
/// during lowering by the GC infrastructure.
bool callsGCLeafFunction(ImmutableCallSite CS, const TargetLibraryInfo &TLI);
/// Copy a nonnull metadata node to a new load instruction.
///
/// This handles mapping it to range metadata if the new load is an integer
/// load instead of a pointer load.
void copyNonnullMetadata(const LoadInst &OldLI, MDNode *N, LoadInst &NewLI);
/// Copy a range metadata node to a new load instruction.
///
/// This handles mapping it to nonnull metadata if the new load is a pointer
/// load instead of an integer load and the range doesn't cover null.
void copyRangeMetadata(const DataLayout &DL, const LoadInst &OldLI, MDNode *N,
LoadInst &NewLI);
//===----------------------------------------------------------------------===//
// Intrinsic pattern matching
//
/// Try to match a bswap or bitreverse idiom.
///
/// If an idiom is matched, an intrinsic call is inserted before \c I. Any added
/// instructions are returned in \c InsertedInsts. They will all have been added
/// to a basic block.
///
/// A bitreverse idiom normally requires around 2*BW nodes to be searched (where
/// BW is the bitwidth of the integer type). A bswap idiom requires anywhere up
/// to BW / 4 nodes to be searched, so is significantly faster.
///
/// This function returns true on a successful match or false otherwise.
bool recognizeBSwapOrBitReverseIdiom(
Instruction *I, bool MatchBSwaps, bool MatchBitReversals,
SmallVectorImpl<Instruction *> &InsertedInsts);
//===----------------------------------------------------------------------===//
// Sanitizer utilities
//
/// Given a CallInst, check if it calls a string function known to CodeGen,
/// and mark it with NoBuiltin if so. To be used by sanitizers that intend
/// to intercept string functions and want to avoid converting them to target
/// specific instructions.
void maybeMarkSanitizerLibraryCallNoBuiltin(CallInst *CI,
const TargetLibraryInfo *TLI);
//===----------------------------------------------------------------------===//
// Transform predicates
//
/// Given an instruction, is it legal to set operand OpIdx to a non-constant
/// value?
bool canReplaceOperandWithVariable(const Instruction *I, unsigned OpIdx);
} // end namespace llvm
#endif // LLVM_TRANSFORMS_UTILS_LOCAL_H
|