forked from OSchip/llvm-project
1360 lines
52 KiB
C++
1360 lines
52 KiB
C++
//===-- Local.cpp - Functions to perform local transformations ------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This family of functions perform various local transformations to the
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// program.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Utils/Local.h"
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Analysis/LibCallSemantics.h"
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#include "llvm/Analysis/InstructionSimplify.h"
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#include "llvm/Analysis/MemoryBuiltins.h"
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#include "llvm/Analysis/ValueTracking.h"
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#include "llvm/IR/CFG.h"
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#include "llvm/IR/Constants.h"
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#include "llvm/IR/DIBuilder.h"
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/DebugInfo.h"
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#include "llvm/IR/DerivedTypes.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/GetElementPtrTypeIterator.h"
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#include "llvm/IR/GlobalAlias.h"
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#include "llvm/IR/GlobalVariable.h"
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#include "llvm/IR/IRBuilder.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/IntrinsicInst.h"
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#include "llvm/IR/Intrinsics.h"
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#include "llvm/IR/MDBuilder.h"
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#include "llvm/IR/Metadata.h"
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#include "llvm/IR/Operator.h"
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#include "llvm/IR/ValueHandle.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/MathExtras.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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#define DEBUG_TYPE "local"
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STATISTIC(NumRemoved, "Number of unreachable basic blocks removed");
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//===----------------------------------------------------------------------===//
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// Local constant propagation.
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//
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/// ConstantFoldTerminator - If a terminator instruction is predicated on a
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/// constant value, convert it into an unconditional branch to the constant
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/// destination. This is a nontrivial operation because the successors of this
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/// basic block must have their PHI nodes updated.
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/// Also calls RecursivelyDeleteTriviallyDeadInstructions() on any branch/switch
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/// conditions and indirectbr addresses this might make dead if
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/// DeleteDeadConditions is true.
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bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions,
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const TargetLibraryInfo *TLI) {
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TerminatorInst *T = BB->getTerminator();
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IRBuilder<> Builder(T);
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// Branch - See if we are conditional jumping on constant
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if (BranchInst *BI = dyn_cast<BranchInst>(T)) {
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if (BI->isUnconditional()) return false; // Can't optimize uncond branch
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BasicBlock *Dest1 = BI->getSuccessor(0);
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BasicBlock *Dest2 = BI->getSuccessor(1);
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if (ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition())) {
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// Are we branching on constant?
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// YES. Change to unconditional branch...
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BasicBlock *Destination = Cond->getZExtValue() ? Dest1 : Dest2;
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BasicBlock *OldDest = Cond->getZExtValue() ? Dest2 : Dest1;
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//cerr << "Function: " << T->getParent()->getParent()
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// << "\nRemoving branch from " << T->getParent()
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// << "\n\nTo: " << OldDest << endl;
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// Let the basic block know that we are letting go of it. Based on this,
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// it will adjust it's PHI nodes.
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OldDest->removePredecessor(BB);
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// Replace the conditional branch with an unconditional one.
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Builder.CreateBr(Destination);
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BI->eraseFromParent();
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return true;
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}
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if (Dest2 == Dest1) { // Conditional branch to same location?
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// This branch matches something like this:
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// br bool %cond, label %Dest, label %Dest
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// and changes it into: br label %Dest
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// Let the basic block know that we are letting go of one copy of it.
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assert(BI->getParent() && "Terminator not inserted in block!");
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Dest1->removePredecessor(BI->getParent());
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// Replace the conditional branch with an unconditional one.
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Builder.CreateBr(Dest1);
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Value *Cond = BI->getCondition();
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BI->eraseFromParent();
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if (DeleteDeadConditions)
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RecursivelyDeleteTriviallyDeadInstructions(Cond, TLI);
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return true;
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}
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return false;
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}
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if (SwitchInst *SI = dyn_cast<SwitchInst>(T)) {
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// If we are switching on a constant, we can convert the switch to an
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// unconditional branch.
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ConstantInt *CI = dyn_cast<ConstantInt>(SI->getCondition());
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BasicBlock *DefaultDest = SI->getDefaultDest();
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BasicBlock *TheOnlyDest = DefaultDest;
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// If the default is unreachable, ignore it when searching for TheOnlyDest.
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if (isa<UnreachableInst>(DefaultDest->getFirstNonPHIOrDbg()) &&
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SI->getNumCases() > 0) {
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TheOnlyDest = SI->case_begin().getCaseSuccessor();
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}
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// Figure out which case it goes to.
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for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end();
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i != e; ++i) {
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// Found case matching a constant operand?
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if (i.getCaseValue() == CI) {
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TheOnlyDest = i.getCaseSuccessor();
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break;
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}
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// Check to see if this branch is going to the same place as the default
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// dest. If so, eliminate it as an explicit compare.
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if (i.getCaseSuccessor() == DefaultDest) {
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MDNode *MD = SI->getMetadata(LLVMContext::MD_prof);
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unsigned NCases = SI->getNumCases();
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// Fold the case metadata into the default if there will be any branches
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// left, unless the metadata doesn't match the switch.
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if (NCases > 1 && MD && MD->getNumOperands() == 2 + NCases) {
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// Collect branch weights into a vector.
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SmallVector<uint32_t, 8> Weights;
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for (unsigned MD_i = 1, MD_e = MD->getNumOperands(); MD_i < MD_e;
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++MD_i) {
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ConstantInt *CI =
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mdconst::dyn_extract<ConstantInt>(MD->getOperand(MD_i));
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assert(CI);
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Weights.push_back(CI->getValue().getZExtValue());
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}
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// Merge weight of this case to the default weight.
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unsigned idx = i.getCaseIndex();
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Weights[0] += Weights[idx+1];
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// Remove weight for this case.
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std::swap(Weights[idx+1], Weights.back());
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Weights.pop_back();
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SI->setMetadata(LLVMContext::MD_prof,
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MDBuilder(BB->getContext()).
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createBranchWeights(Weights));
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}
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// Remove this entry.
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DefaultDest->removePredecessor(SI->getParent());
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SI->removeCase(i);
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--i; --e;
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continue;
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}
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// Otherwise, check to see if the switch only branches to one destination.
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// We do this by reseting "TheOnlyDest" to null when we find two non-equal
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// destinations.
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if (i.getCaseSuccessor() != TheOnlyDest) TheOnlyDest = nullptr;
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}
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if (CI && !TheOnlyDest) {
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// Branching on a constant, but not any of the cases, go to the default
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// successor.
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TheOnlyDest = SI->getDefaultDest();
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}
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// If we found a single destination that we can fold the switch into, do so
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// now.
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if (TheOnlyDest) {
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// Insert the new branch.
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Builder.CreateBr(TheOnlyDest);
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BasicBlock *BB = SI->getParent();
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// Remove entries from PHI nodes which we no longer branch to...
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for (unsigned i = 0, e = SI->getNumSuccessors(); i != e; ++i) {
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// Found case matching a constant operand?
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BasicBlock *Succ = SI->getSuccessor(i);
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if (Succ == TheOnlyDest)
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TheOnlyDest = nullptr; // Don't modify the first branch to TheOnlyDest
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else
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Succ->removePredecessor(BB);
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}
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// Delete the old switch.
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Value *Cond = SI->getCondition();
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SI->eraseFromParent();
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if (DeleteDeadConditions)
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RecursivelyDeleteTriviallyDeadInstructions(Cond, TLI);
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return true;
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}
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if (SI->getNumCases() == 1) {
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// Otherwise, we can fold this switch into a conditional branch
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// instruction if it has only one non-default destination.
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SwitchInst::CaseIt FirstCase = SI->case_begin();
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Value *Cond = Builder.CreateICmpEQ(SI->getCondition(),
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FirstCase.getCaseValue(), "cond");
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// Insert the new branch.
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BranchInst *NewBr = Builder.CreateCondBr(Cond,
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FirstCase.getCaseSuccessor(),
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SI->getDefaultDest());
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MDNode *MD = SI->getMetadata(LLVMContext::MD_prof);
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if (MD && MD->getNumOperands() == 3) {
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ConstantInt *SICase =
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mdconst::dyn_extract<ConstantInt>(MD->getOperand(2));
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ConstantInt *SIDef =
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mdconst::dyn_extract<ConstantInt>(MD->getOperand(1));
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assert(SICase && SIDef);
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// The TrueWeight should be the weight for the single case of SI.
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NewBr->setMetadata(LLVMContext::MD_prof,
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MDBuilder(BB->getContext()).
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createBranchWeights(SICase->getValue().getZExtValue(),
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SIDef->getValue().getZExtValue()));
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}
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// Delete the old switch.
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SI->eraseFromParent();
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return true;
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}
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return false;
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}
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if (IndirectBrInst *IBI = dyn_cast<IndirectBrInst>(T)) {
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// indirectbr blockaddress(@F, @BB) -> br label @BB
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if (BlockAddress *BA =
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dyn_cast<BlockAddress>(IBI->getAddress()->stripPointerCasts())) {
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BasicBlock *TheOnlyDest = BA->getBasicBlock();
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// Insert the new branch.
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Builder.CreateBr(TheOnlyDest);
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for (unsigned i = 0, e = IBI->getNumDestinations(); i != e; ++i) {
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if (IBI->getDestination(i) == TheOnlyDest)
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TheOnlyDest = nullptr;
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else
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IBI->getDestination(i)->removePredecessor(IBI->getParent());
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}
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Value *Address = IBI->getAddress();
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IBI->eraseFromParent();
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if (DeleteDeadConditions)
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RecursivelyDeleteTriviallyDeadInstructions(Address, TLI);
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// If we didn't find our destination in the IBI successor list, then we
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// have undefined behavior. Replace the unconditional branch with an
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// 'unreachable' instruction.
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if (TheOnlyDest) {
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BB->getTerminator()->eraseFromParent();
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new UnreachableInst(BB->getContext(), BB);
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}
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return true;
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}
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}
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return false;
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}
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//===----------------------------------------------------------------------===//
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// Local dead code elimination.
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//
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/// isInstructionTriviallyDead - Return true if the result produced by the
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/// instruction is not used, and the instruction has no side effects.
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///
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bool llvm::isInstructionTriviallyDead(Instruction *I,
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const TargetLibraryInfo *TLI) {
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if (!I->use_empty() || isa<TerminatorInst>(I)) return false;
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// We don't want the landingpad instruction removed by anything this general.
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if (isa<LandingPadInst>(I))
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return false;
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// We don't want debug info removed by anything this general, unless
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// debug info is empty.
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if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(I)) {
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if (DDI->getAddress())
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return false;
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return true;
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}
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if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(I)) {
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if (DVI->getValue())
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return false;
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return true;
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}
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if (!I->mayHaveSideEffects()) return true;
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// Special case intrinsics that "may have side effects" but can be deleted
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// when dead.
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if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
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// Safe to delete llvm.stacksave if dead.
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if (II->getIntrinsicID() == Intrinsic::stacksave)
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return true;
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// Lifetime intrinsics are dead when their right-hand is undef.
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if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
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II->getIntrinsicID() == Intrinsic::lifetime_end)
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return isa<UndefValue>(II->getArgOperand(1));
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// Assumptions are dead if their condition is trivially true.
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if (II->getIntrinsicID() == Intrinsic::assume) {
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if (ConstantInt *Cond = dyn_cast<ConstantInt>(II->getArgOperand(0)))
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return !Cond->isZero();
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return false;
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}
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}
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if (isAllocLikeFn(I, TLI)) return true;
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if (CallInst *CI = isFreeCall(I, TLI))
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if (Constant *C = dyn_cast<Constant>(CI->getArgOperand(0)))
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return C->isNullValue() || isa<UndefValue>(C);
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return false;
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}
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/// RecursivelyDeleteTriviallyDeadInstructions - If the specified value is a
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/// trivially dead instruction, delete it. If that makes any of its operands
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/// trivially dead, delete them too, recursively. Return true if any
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/// instructions were deleted.
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bool
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llvm::RecursivelyDeleteTriviallyDeadInstructions(Value *V,
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const TargetLibraryInfo *TLI) {
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Instruction *I = dyn_cast<Instruction>(V);
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if (!I || !I->use_empty() || !isInstructionTriviallyDead(I, TLI))
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return false;
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SmallVector<Instruction*, 16> DeadInsts;
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DeadInsts.push_back(I);
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do {
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I = DeadInsts.pop_back_val();
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// Null out all of the instruction's operands to see if any operand becomes
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// dead as we go.
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for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
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Value *OpV = I->getOperand(i);
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I->setOperand(i, nullptr);
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if (!OpV->use_empty()) continue;
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// If the operand is an instruction that became dead as we nulled out the
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// operand, and if it is 'trivially' dead, delete it in a future loop
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// iteration.
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if (Instruction *OpI = dyn_cast<Instruction>(OpV))
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if (isInstructionTriviallyDead(OpI, TLI))
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DeadInsts.push_back(OpI);
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}
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I->eraseFromParent();
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} while (!DeadInsts.empty());
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return true;
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}
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/// areAllUsesEqual - Check whether the uses of a value are all the same.
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/// This is similar to Instruction::hasOneUse() except this will also return
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/// true when there are no uses or multiple uses that all refer to the same
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/// value.
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static bool areAllUsesEqual(Instruction *I) {
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Value::user_iterator UI = I->user_begin();
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Value::user_iterator UE = I->user_end();
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if (UI == UE)
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return true;
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User *TheUse = *UI;
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for (++UI; UI != UE; ++UI) {
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if (*UI != TheUse)
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return false;
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}
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return true;
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}
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/// RecursivelyDeleteDeadPHINode - If the specified value is an effectively
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/// dead PHI node, due to being a def-use chain of single-use nodes that
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/// either forms a cycle or is terminated by a trivially dead instruction,
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/// delete it. If that makes any of its operands trivially dead, delete them
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/// too, recursively. Return true if a change was made.
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bool llvm::RecursivelyDeleteDeadPHINode(PHINode *PN,
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const TargetLibraryInfo *TLI) {
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SmallPtrSet<Instruction*, 4> Visited;
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for (Instruction *I = PN; areAllUsesEqual(I) && !I->mayHaveSideEffects();
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I = cast<Instruction>(*I->user_begin())) {
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if (I->use_empty())
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return RecursivelyDeleteTriviallyDeadInstructions(I, TLI);
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// If we find an instruction more than once, we're on a cycle that
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// won't prove fruitful.
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if (!Visited.insert(I).second) {
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// Break the cycle and delete the instruction and its operands.
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I->replaceAllUsesWith(UndefValue::get(I->getType()));
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(void)RecursivelyDeleteTriviallyDeadInstructions(I, TLI);
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return true;
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}
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}
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return false;
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}
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/// SimplifyInstructionsInBlock - Scan the specified basic block and try to
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/// simplify any instructions in it and recursively delete dead instructions.
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///
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/// This returns true if it changed the code, note that it can delete
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/// instructions in other blocks as well in this block.
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bool llvm::SimplifyInstructionsInBlock(BasicBlock *BB, const DataLayout *TD,
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const TargetLibraryInfo *TLI) {
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bool MadeChange = false;
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#ifndef NDEBUG
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// In debug builds, ensure that the terminator of the block is never replaced
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// or deleted by these simplifications. The idea of simplification is that it
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// cannot introduce new instructions, and there is no way to replace the
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// terminator of a block without introducing a new instruction.
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AssertingVH<Instruction> TerminatorVH(--BB->end());
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#endif
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for (BasicBlock::iterator BI = BB->begin(), E = --BB->end(); BI != E; ) {
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assert(!BI->isTerminator());
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Instruction *Inst = BI++;
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WeakVH BIHandle(BI);
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if (recursivelySimplifyInstruction(Inst, TD, TLI)) {
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MadeChange = true;
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if (BIHandle != BI)
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BI = BB->begin();
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continue;
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}
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MadeChange |= RecursivelyDeleteTriviallyDeadInstructions(Inst, TLI);
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if (BIHandle != BI)
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BI = BB->begin();
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}
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return MadeChange;
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}
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//===----------------------------------------------------------------------===//
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// Control Flow Graph Restructuring.
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//
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/// RemovePredecessorAndSimplify - Like BasicBlock::removePredecessor, this
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/// method is called when we're about to delete Pred as a predecessor of BB. If
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/// BB contains any PHI nodes, this drops the entries in the PHI nodes for Pred.
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///
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/// Unlike the removePredecessor method, this attempts to simplify uses of PHI
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/// nodes that collapse into identity values. For example, if we have:
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/// x = phi(1, 0, 0, 0)
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/// y = and x, z
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///
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/// .. and delete the predecessor corresponding to the '1', this will attempt to
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/// recursively fold the and to 0.
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void llvm::RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred,
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DataLayout *TD) {
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// This only adjusts blocks with PHI nodes.
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if (!isa<PHINode>(BB->begin()))
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return;
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// Remove the entries for Pred from the PHI nodes in BB, but do not simplify
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// them down. This will leave us with single entry phi nodes and other phis
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// that can be removed.
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BB->removePredecessor(Pred, true);
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WeakVH PhiIt = &BB->front();
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while (PHINode *PN = dyn_cast<PHINode>(PhiIt)) {
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PhiIt = &*++BasicBlock::iterator(cast<Instruction>(PhiIt));
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Value *OldPhiIt = PhiIt;
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if (!recursivelySimplifyInstruction(PN, TD))
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continue;
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|
|
// If recursive simplification ended up deleting the next PHI node we would
|
|
// iterate to, then our iterator is invalid, restart scanning from the top
|
|
// of the block.
|
|
if (PhiIt != OldPhiIt) PhiIt = &BB->front();
|
|
}
|
|
}
|
|
|
|
|
|
/// MergeBasicBlockIntoOnlyPred - DestBB is a block with one predecessor and its
|
|
/// predecessor is known to have one successor (DestBB!). Eliminate the edge
|
|
/// between them, moving the instructions in the predecessor into DestBB and
|
|
/// deleting the predecessor block.
|
|
///
|
|
void llvm::MergeBasicBlockIntoOnlyPred(BasicBlock *DestBB, DominatorTree *DT) {
|
|
// If BB has single-entry PHI nodes, fold them.
|
|
while (PHINode *PN = dyn_cast<PHINode>(DestBB->begin())) {
|
|
Value *NewVal = PN->getIncomingValue(0);
|
|
// Replace self referencing PHI with undef, it must be dead.
|
|
if (NewVal == PN) NewVal = UndefValue::get(PN->getType());
|
|
PN->replaceAllUsesWith(NewVal);
|
|
PN->eraseFromParent();
|
|
}
|
|
|
|
BasicBlock *PredBB = DestBB->getSinglePredecessor();
|
|
assert(PredBB && "Block doesn't have a single predecessor!");
|
|
|
|
// Zap anything that took the address of DestBB. Not doing this will give the
|
|
// address an invalid value.
|
|
if (DestBB->hasAddressTaken()) {
|
|
BlockAddress *BA = BlockAddress::get(DestBB);
|
|
Constant *Replacement =
|
|
ConstantInt::get(llvm::Type::getInt32Ty(BA->getContext()), 1);
|
|
BA->replaceAllUsesWith(ConstantExpr::getIntToPtr(Replacement,
|
|
BA->getType()));
|
|
BA->destroyConstant();
|
|
}
|
|
|
|
// Anything that branched to PredBB now branches to DestBB.
|
|
PredBB->replaceAllUsesWith(DestBB);
|
|
|
|
// Splice all the instructions from PredBB to DestBB.
|
|
PredBB->getTerminator()->eraseFromParent();
|
|
DestBB->getInstList().splice(DestBB->begin(), PredBB->getInstList());
|
|
|
|
// If the PredBB is the entry block of the function, move DestBB up to
|
|
// become the entry block after we erase PredBB.
|
|
if (PredBB == &DestBB->getParent()->getEntryBlock())
|
|
DestBB->moveAfter(PredBB);
|
|
|
|
if (DT) {
|
|
BasicBlock *PredBBIDom = DT->getNode(PredBB)->getIDom()->getBlock();
|
|
DT->changeImmediateDominator(DestBB, PredBBIDom);
|
|
DT->eraseNode(PredBB);
|
|
}
|
|
// Nuke BB.
|
|
PredBB->eraseFromParent();
|
|
}
|
|
|
|
/// CanMergeValues - Return true if we can choose one of these values to use
|
|
/// in place of the other. Note that we will always choose the non-undef
|
|
/// value to keep.
|
|
static bool CanMergeValues(Value *First, Value *Second) {
|
|
return First == Second || isa<UndefValue>(First) || isa<UndefValue>(Second);
|
|
}
|
|
|
|
/// CanPropagatePredecessorsForPHIs - Return true if we can fold BB, an
|
|
/// almost-empty BB ending in an unconditional branch to Succ, into Succ.
|
|
///
|
|
/// Assumption: Succ is the single successor for BB.
|
|
///
|
|
static bool CanPropagatePredecessorsForPHIs(BasicBlock *BB, BasicBlock *Succ) {
|
|
assert(*succ_begin(BB) == Succ && "Succ is not successor of BB!");
|
|
|
|
DEBUG(dbgs() << "Looking to fold " << BB->getName() << " into "
|
|
<< Succ->getName() << "\n");
|
|
// Shortcut, if there is only a single predecessor it must be BB and merging
|
|
// is always safe
|
|
if (Succ->getSinglePredecessor()) return true;
|
|
|
|
// Make a list of the predecessors of BB
|
|
SmallPtrSet<BasicBlock*, 16> BBPreds(pred_begin(BB), pred_end(BB));
|
|
|
|
// Look at all the phi nodes in Succ, to see if they present a conflict when
|
|
// merging these blocks
|
|
for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
|
|
PHINode *PN = cast<PHINode>(I);
|
|
|
|
// If the incoming value from BB is again a PHINode in
|
|
// BB which has the same incoming value for *PI as PN does, we can
|
|
// merge the phi nodes and then the blocks can still be merged
|
|
PHINode *BBPN = dyn_cast<PHINode>(PN->getIncomingValueForBlock(BB));
|
|
if (BBPN && BBPN->getParent() == BB) {
|
|
for (unsigned PI = 0, PE = PN->getNumIncomingValues(); PI != PE; ++PI) {
|
|
BasicBlock *IBB = PN->getIncomingBlock(PI);
|
|
if (BBPreds.count(IBB) &&
|
|
!CanMergeValues(BBPN->getIncomingValueForBlock(IBB),
|
|
PN->getIncomingValue(PI))) {
|
|
DEBUG(dbgs() << "Can't fold, phi node " << PN->getName() << " in "
|
|
<< Succ->getName() << " is conflicting with "
|
|
<< BBPN->getName() << " with regard to common predecessor "
|
|
<< IBB->getName() << "\n");
|
|
return false;
|
|
}
|
|
}
|
|
} else {
|
|
Value* Val = PN->getIncomingValueForBlock(BB);
|
|
for (unsigned PI = 0, PE = PN->getNumIncomingValues(); PI != PE; ++PI) {
|
|
// See if the incoming value for the common predecessor is equal to the
|
|
// one for BB, in which case this phi node will not prevent the merging
|
|
// of the block.
|
|
BasicBlock *IBB = PN->getIncomingBlock(PI);
|
|
if (BBPreds.count(IBB) &&
|
|
!CanMergeValues(Val, PN->getIncomingValue(PI))) {
|
|
DEBUG(dbgs() << "Can't fold, phi node " << PN->getName() << " in "
|
|
<< Succ->getName() << " is conflicting with regard to common "
|
|
<< "predecessor " << IBB->getName() << "\n");
|
|
return false;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
typedef SmallVector<BasicBlock *, 16> PredBlockVector;
|
|
typedef DenseMap<BasicBlock *, Value *> IncomingValueMap;
|
|
|
|
/// \brief Determines the value to use as the phi node input for a block.
|
|
///
|
|
/// Select between \p OldVal any value that we know flows from \p BB
|
|
/// to a particular phi on the basis of which one (if either) is not
|
|
/// undef. Update IncomingValues based on the selected value.
|
|
///
|
|
/// \param OldVal The value we are considering selecting.
|
|
/// \param BB The block that the value flows in from.
|
|
/// \param IncomingValues A map from block-to-value for other phi inputs
|
|
/// that we have examined.
|
|
///
|
|
/// \returns the selected value.
|
|
static Value *selectIncomingValueForBlock(Value *OldVal, BasicBlock *BB,
|
|
IncomingValueMap &IncomingValues) {
|
|
if (!isa<UndefValue>(OldVal)) {
|
|
assert((!IncomingValues.count(BB) ||
|
|
IncomingValues.find(BB)->second == OldVal) &&
|
|
"Expected OldVal to match incoming value from BB!");
|
|
|
|
IncomingValues.insert(std::make_pair(BB, OldVal));
|
|
return OldVal;
|
|
}
|
|
|
|
IncomingValueMap::const_iterator It = IncomingValues.find(BB);
|
|
if (It != IncomingValues.end()) return It->second;
|
|
|
|
return OldVal;
|
|
}
|
|
|
|
/// \brief Create a map from block to value for the operands of a
|
|
/// given phi.
|
|
///
|
|
/// Create a map from block to value for each non-undef value flowing
|
|
/// into \p PN.
|
|
///
|
|
/// \param PN The phi we are collecting the map for.
|
|
/// \param IncomingValues [out] The map from block to value for this phi.
|
|
static void gatherIncomingValuesToPhi(PHINode *PN,
|
|
IncomingValueMap &IncomingValues) {
|
|
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
|
|
BasicBlock *BB = PN->getIncomingBlock(i);
|
|
Value *V = PN->getIncomingValue(i);
|
|
|
|
if (!isa<UndefValue>(V))
|
|
IncomingValues.insert(std::make_pair(BB, V));
|
|
}
|
|
}
|
|
|
|
/// \brief Replace the incoming undef values to a phi with the values
|
|
/// from a block-to-value map.
|
|
///
|
|
/// \param PN The phi we are replacing the undefs in.
|
|
/// \param IncomingValues A map from block to value.
|
|
static void replaceUndefValuesInPhi(PHINode *PN,
|
|
const IncomingValueMap &IncomingValues) {
|
|
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
|
|
Value *V = PN->getIncomingValue(i);
|
|
|
|
if (!isa<UndefValue>(V)) continue;
|
|
|
|
BasicBlock *BB = PN->getIncomingBlock(i);
|
|
IncomingValueMap::const_iterator It = IncomingValues.find(BB);
|
|
if (It == IncomingValues.end()) continue;
|
|
|
|
PN->setIncomingValue(i, It->second);
|
|
}
|
|
}
|
|
|
|
/// \brief Replace a value flowing from a block to a phi with
|
|
/// potentially multiple instances of that value flowing from the
|
|
/// block's predecessors to the phi.
|
|
///
|
|
/// \param BB The block with the value flowing into the phi.
|
|
/// \param BBPreds The predecessors of BB.
|
|
/// \param PN The phi that we are updating.
|
|
static void redirectValuesFromPredecessorsToPhi(BasicBlock *BB,
|
|
const PredBlockVector &BBPreds,
|
|
PHINode *PN) {
|
|
Value *OldVal = PN->removeIncomingValue(BB, false);
|
|
assert(OldVal && "No entry in PHI for Pred BB!");
|
|
|
|
IncomingValueMap IncomingValues;
|
|
|
|
// We are merging two blocks - BB, and the block containing PN - and
|
|
// as a result we need to redirect edges from the predecessors of BB
|
|
// to go to the block containing PN, and update PN
|
|
// accordingly. Since we allow merging blocks in the case where the
|
|
// predecessor and successor blocks both share some predecessors,
|
|
// and where some of those common predecessors might have undef
|
|
// values flowing into PN, we want to rewrite those values to be
|
|
// consistent with the non-undef values.
|
|
|
|
gatherIncomingValuesToPhi(PN, IncomingValues);
|
|
|
|
// If this incoming value is one of the PHI nodes in BB, the new entries
|
|
// in the PHI node are the entries from the old PHI.
|
|
if (isa<PHINode>(OldVal) && cast<PHINode>(OldVal)->getParent() == BB) {
|
|
PHINode *OldValPN = cast<PHINode>(OldVal);
|
|
for (unsigned i = 0, e = OldValPN->getNumIncomingValues(); i != e; ++i) {
|
|
// Note that, since we are merging phi nodes and BB and Succ might
|
|
// have common predecessors, we could end up with a phi node with
|
|
// identical incoming branches. This will be cleaned up later (and
|
|
// will trigger asserts if we try to clean it up now, without also
|
|
// simplifying the corresponding conditional branch).
|
|
BasicBlock *PredBB = OldValPN->getIncomingBlock(i);
|
|
Value *PredVal = OldValPN->getIncomingValue(i);
|
|
Value *Selected = selectIncomingValueForBlock(PredVal, PredBB,
|
|
IncomingValues);
|
|
|
|
// And add a new incoming value for this predecessor for the
|
|
// newly retargeted branch.
|
|
PN->addIncoming(Selected, PredBB);
|
|
}
|
|
} else {
|
|
for (unsigned i = 0, e = BBPreds.size(); i != e; ++i) {
|
|
// Update existing incoming values in PN for this
|
|
// predecessor of BB.
|
|
BasicBlock *PredBB = BBPreds[i];
|
|
Value *Selected = selectIncomingValueForBlock(OldVal, PredBB,
|
|
IncomingValues);
|
|
|
|
// And add a new incoming value for this predecessor for the
|
|
// newly retargeted branch.
|
|
PN->addIncoming(Selected, PredBB);
|
|
}
|
|
}
|
|
|
|
replaceUndefValuesInPhi(PN, IncomingValues);
|
|
}
|
|
|
|
/// TryToSimplifyUncondBranchFromEmptyBlock - BB is known to contain an
|
|
/// unconditional branch, and contains no instructions other than PHI nodes,
|
|
/// potential side-effect free 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 llvm::TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB) {
|
|
assert(BB != &BB->getParent()->getEntryBlock() &&
|
|
"TryToSimplifyUncondBranchFromEmptyBlock called on entry block!");
|
|
|
|
// We can't eliminate infinite loops.
|
|
BasicBlock *Succ = cast<BranchInst>(BB->getTerminator())->getSuccessor(0);
|
|
if (BB == Succ) return false;
|
|
|
|
// Check to see if merging these blocks would cause conflicts for any of the
|
|
// phi nodes in BB or Succ. If not, we can safely merge.
|
|
if (!CanPropagatePredecessorsForPHIs(BB, Succ)) return false;
|
|
|
|
// Check for cases where Succ has multiple predecessors and a PHI node in BB
|
|
// has uses which will not disappear when the PHI nodes are merged. It is
|
|
// possible to handle such cases, but difficult: it requires checking whether
|
|
// BB dominates Succ, which is non-trivial to calculate in the case where
|
|
// Succ has multiple predecessors. Also, it requires checking whether
|
|
// constructing the necessary self-referential PHI node doesn't introduce any
|
|
// conflicts; this isn't too difficult, but the previous code for doing this
|
|
// was incorrect.
|
|
//
|
|
// Note that if this check finds a live use, BB dominates Succ, so BB is
|
|
// something like a loop pre-header (or rarely, a part of an irreducible CFG);
|
|
// folding the branch isn't profitable in that case anyway.
|
|
if (!Succ->getSinglePredecessor()) {
|
|
BasicBlock::iterator BBI = BB->begin();
|
|
while (isa<PHINode>(*BBI)) {
|
|
for (Use &U : BBI->uses()) {
|
|
if (PHINode* PN = dyn_cast<PHINode>(U.getUser())) {
|
|
if (PN->getIncomingBlock(U) != BB)
|
|
return false;
|
|
} else {
|
|
return false;
|
|
}
|
|
}
|
|
++BBI;
|
|
}
|
|
}
|
|
|
|
DEBUG(dbgs() << "Killing Trivial BB: \n" << *BB);
|
|
|
|
if (isa<PHINode>(Succ->begin())) {
|
|
// If there is more than one pred of succ, and there are PHI nodes in
|
|
// the successor, then we need to add incoming edges for the PHI nodes
|
|
//
|
|
const PredBlockVector BBPreds(pred_begin(BB), pred_end(BB));
|
|
|
|
// Loop over all of the PHI nodes in the successor of BB.
|
|
for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
|
|
PHINode *PN = cast<PHINode>(I);
|
|
|
|
redirectValuesFromPredecessorsToPhi(BB, BBPreds, PN);
|
|
}
|
|
}
|
|
|
|
if (Succ->getSinglePredecessor()) {
|
|
// BB is the only predecessor of Succ, so Succ will end up with exactly
|
|
// the same predecessors BB had.
|
|
|
|
// Copy over any phi, debug or lifetime instruction.
|
|
BB->getTerminator()->eraseFromParent();
|
|
Succ->getInstList().splice(Succ->getFirstNonPHI(), BB->getInstList());
|
|
} else {
|
|
while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
|
|
// We explicitly check for such uses in CanPropagatePredecessorsForPHIs.
|
|
assert(PN->use_empty() && "There shouldn't be any uses here!");
|
|
PN->eraseFromParent();
|
|
}
|
|
}
|
|
|
|
// Everything that jumped to BB now goes to Succ.
|
|
BB->replaceAllUsesWith(Succ);
|
|
if (!Succ->hasName()) Succ->takeName(BB);
|
|
BB->eraseFromParent(); // Delete the old basic block.
|
|
return true;
|
|
}
|
|
|
|
/// 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 llvm::EliminateDuplicatePHINodes(BasicBlock *BB) {
|
|
bool Changed = false;
|
|
|
|
// This implementation doesn't currently consider undef operands
|
|
// specially. Theoretically, two phis which are identical except for
|
|
// one having an undef where the other doesn't could be collapsed.
|
|
|
|
// Map from PHI hash values to PHI nodes. If multiple PHIs have
|
|
// the same hash value, the element is the first PHI in the
|
|
// linked list in CollisionMap.
|
|
DenseMap<uintptr_t, PHINode *> HashMap;
|
|
|
|
// Maintain linked lists of PHI nodes with common hash values.
|
|
DenseMap<PHINode *, PHINode *> CollisionMap;
|
|
|
|
// Examine each PHI.
|
|
for (BasicBlock::iterator I = BB->begin();
|
|
PHINode *PN = dyn_cast<PHINode>(I++); ) {
|
|
// Compute a hash value on the operands. Instcombine will likely have sorted
|
|
// them, which helps expose duplicates, but we have to check all the
|
|
// operands to be safe in case instcombine hasn't run.
|
|
uintptr_t Hash = 0;
|
|
// This hash algorithm is quite weak as hash functions go, but it seems
|
|
// to do a good enough job for this particular purpose, and is very quick.
|
|
for (User::op_iterator I = PN->op_begin(), E = PN->op_end(); I != E; ++I) {
|
|
Hash ^= reinterpret_cast<uintptr_t>(static_cast<Value *>(*I));
|
|
Hash = (Hash << 7) | (Hash >> (sizeof(uintptr_t) * CHAR_BIT - 7));
|
|
}
|
|
for (PHINode::block_iterator I = PN->block_begin(), E = PN->block_end();
|
|
I != E; ++I) {
|
|
Hash ^= reinterpret_cast<uintptr_t>(static_cast<BasicBlock *>(*I));
|
|
Hash = (Hash << 7) | (Hash >> (sizeof(uintptr_t) * CHAR_BIT - 7));
|
|
}
|
|
// Avoid colliding with the DenseMap sentinels ~0 and ~0-1.
|
|
Hash >>= 1;
|
|
// If we've never seen this hash value before, it's a unique PHI.
|
|
std::pair<DenseMap<uintptr_t, PHINode *>::iterator, bool> Pair =
|
|
HashMap.insert(std::make_pair(Hash, PN));
|
|
if (Pair.second) continue;
|
|
// Otherwise it's either a duplicate or a hash collision.
|
|
for (PHINode *OtherPN = Pair.first->second; ; ) {
|
|
if (OtherPN->isIdenticalTo(PN)) {
|
|
// A duplicate. Replace this PHI with its duplicate.
|
|
PN->replaceAllUsesWith(OtherPN);
|
|
PN->eraseFromParent();
|
|
Changed = true;
|
|
break;
|
|
}
|
|
// A non-duplicate hash collision.
|
|
DenseMap<PHINode *, PHINode *>::iterator I = CollisionMap.find(OtherPN);
|
|
if (I == CollisionMap.end()) {
|
|
// Set this PHI to be the head of the linked list of colliding PHIs.
|
|
PHINode *Old = Pair.first->second;
|
|
Pair.first->second = PN;
|
|
CollisionMap[PN] = Old;
|
|
break;
|
|
}
|
|
// Proceed to the next PHI in the list.
|
|
OtherPN = I->second;
|
|
}
|
|
}
|
|
|
|
return Changed;
|
|
}
|
|
|
|
/// enforceKnownAlignment - If the specified pointer points to an object that
|
|
/// we control, modify the object's alignment to PrefAlign. This isn't
|
|
/// often possible though. 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.
|
|
///
|
|
static unsigned enforceKnownAlignment(Value *V, unsigned Align,
|
|
unsigned PrefAlign, const DataLayout *TD) {
|
|
V = V->stripPointerCasts();
|
|
|
|
if (AllocaInst *AI = dyn_cast<AllocaInst>(V)) {
|
|
// If the preferred alignment is greater than the natural stack alignment
|
|
// then don't round up. This avoids dynamic stack realignment.
|
|
if (TD && TD->exceedsNaturalStackAlignment(PrefAlign))
|
|
return Align;
|
|
// If there is a requested alignment and if this is an alloca, round up.
|
|
if (AI->getAlignment() >= PrefAlign)
|
|
return AI->getAlignment();
|
|
AI->setAlignment(PrefAlign);
|
|
return PrefAlign;
|
|
}
|
|
|
|
if (auto *GO = dyn_cast<GlobalObject>(V)) {
|
|
// If there is a large requested alignment and we can, bump up the alignment
|
|
// of the global.
|
|
if (GO->isDeclaration())
|
|
return Align;
|
|
// If the memory we set aside for the global may not be the memory used by
|
|
// the final program then it is impossible for us to reliably enforce the
|
|
// preferred alignment.
|
|
if (GO->isWeakForLinker())
|
|
return Align;
|
|
|
|
if (GO->getAlignment() >= PrefAlign)
|
|
return GO->getAlignment();
|
|
// We can only increase the alignment of the global if it has no alignment
|
|
// specified or if it is not assigned a section. If it is assigned a
|
|
// section, the global could be densely packed with other objects in the
|
|
// section, increasing the alignment could cause padding issues.
|
|
if (!GO->hasSection() || GO->getAlignment() == 0)
|
|
GO->setAlignment(PrefAlign);
|
|
return GO->getAlignment();
|
|
}
|
|
|
|
return Align;
|
|
}
|
|
|
|
/// 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 llvm::getOrEnforceKnownAlignment(Value *V, unsigned PrefAlign,
|
|
const DataLayout *DL,
|
|
AssumptionCache *AC,
|
|
const Instruction *CxtI,
|
|
const DominatorTree *DT) {
|
|
assert(V->getType()->isPointerTy() &&
|
|
"getOrEnforceKnownAlignment expects a pointer!");
|
|
unsigned BitWidth = DL ? DL->getPointerTypeSizeInBits(V->getType()) : 64;
|
|
|
|
APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
|
|
computeKnownBits(V, KnownZero, KnownOne, DL, 0, AC, CxtI, DT);
|
|
unsigned TrailZ = KnownZero.countTrailingOnes();
|
|
|
|
// Avoid trouble with ridiculously large TrailZ values, such as
|
|
// those computed from a null pointer.
|
|
TrailZ = std::min(TrailZ, unsigned(sizeof(unsigned) * CHAR_BIT - 1));
|
|
|
|
unsigned Align = 1u << std::min(BitWidth - 1, TrailZ);
|
|
|
|
// LLVM doesn't support alignments larger than this currently.
|
|
Align = std::min(Align, +Value::MaximumAlignment);
|
|
|
|
if (PrefAlign > Align)
|
|
Align = enforceKnownAlignment(V, Align, PrefAlign, DL);
|
|
|
|
// We don't need to make any adjustment.
|
|
return Align;
|
|
}
|
|
|
|
///===---------------------------------------------------------------------===//
|
|
/// Dbg Intrinsic utilities
|
|
///
|
|
|
|
/// See if there is a dbg.value intrinsic for DIVar before I.
|
|
static bool LdStHasDebugValue(DIVariable &DIVar, Instruction *I) {
|
|
// Since we can't guarantee that the original dbg.declare instrinsic
|
|
// is removed by LowerDbgDeclare(), we need to make sure that we are
|
|
// not inserting the same dbg.value intrinsic over and over.
|
|
llvm::BasicBlock::InstListType::iterator PrevI(I);
|
|
if (PrevI != I->getParent()->getInstList().begin()) {
|
|
--PrevI;
|
|
if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(PrevI))
|
|
if (DVI->getValue() == I->getOperand(0) &&
|
|
DVI->getOffset() == 0 &&
|
|
DVI->getVariable() == DIVar)
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/// Inserts a llvm.dbg.value intrinsic before a store to an alloca'd value
|
|
/// that has an associated llvm.dbg.decl intrinsic.
|
|
bool llvm::ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
|
|
StoreInst *SI, DIBuilder &Builder) {
|
|
DIVariable DIVar(DDI->getVariable());
|
|
DIExpression DIExpr(DDI->getExpression());
|
|
assert((!DIVar || DIVar.isVariable()) &&
|
|
"Variable in DbgDeclareInst should be either null or a DIVariable.");
|
|
if (!DIVar)
|
|
return false;
|
|
|
|
if (LdStHasDebugValue(DIVar, SI))
|
|
return true;
|
|
|
|
Instruction *DbgVal = nullptr;
|
|
// If an argument is zero extended then use argument directly. The ZExt
|
|
// may be zapped by an optimization pass in future.
|
|
Argument *ExtendedArg = nullptr;
|
|
if (ZExtInst *ZExt = dyn_cast<ZExtInst>(SI->getOperand(0)))
|
|
ExtendedArg = dyn_cast<Argument>(ZExt->getOperand(0));
|
|
if (SExtInst *SExt = dyn_cast<SExtInst>(SI->getOperand(0)))
|
|
ExtendedArg = dyn_cast<Argument>(SExt->getOperand(0));
|
|
if (ExtendedArg)
|
|
DbgVal = Builder.insertDbgValueIntrinsic(ExtendedArg, 0, DIVar, DIExpr, SI);
|
|
else
|
|
DbgVal = Builder.insertDbgValueIntrinsic(SI->getOperand(0), 0, DIVar,
|
|
DIExpr, SI);
|
|
DbgVal->setDebugLoc(DDI->getDebugLoc());
|
|
return true;
|
|
}
|
|
|
|
/// Inserts a llvm.dbg.value intrinsic before a load of an alloca'd value
|
|
/// that has an associated llvm.dbg.decl intrinsic.
|
|
bool llvm::ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
|
|
LoadInst *LI, DIBuilder &Builder) {
|
|
DIVariable DIVar(DDI->getVariable());
|
|
DIExpression DIExpr(DDI->getExpression());
|
|
assert((!DIVar || DIVar.isVariable()) &&
|
|
"Variable in DbgDeclareInst should be either null or a DIVariable.");
|
|
if (!DIVar)
|
|
return false;
|
|
|
|
if (LdStHasDebugValue(DIVar, LI))
|
|
return true;
|
|
|
|
Instruction *DbgVal =
|
|
Builder.insertDbgValueIntrinsic(LI->getOperand(0), 0, DIVar, DIExpr, LI);
|
|
DbgVal->setDebugLoc(DDI->getDebugLoc());
|
|
return true;
|
|
}
|
|
|
|
/// Determine whether this alloca is either a VLA or an array.
|
|
static bool isArray(AllocaInst *AI) {
|
|
return AI->isArrayAllocation() ||
|
|
AI->getType()->getElementType()->isArrayTy();
|
|
}
|
|
|
|
/// LowerDbgDeclare - Lowers llvm.dbg.declare intrinsics into appropriate set
|
|
/// of llvm.dbg.value intrinsics.
|
|
bool llvm::LowerDbgDeclare(Function &F) {
|
|
DIBuilder DIB(*F.getParent(), /*AllowUnresolved*/ false);
|
|
SmallVector<DbgDeclareInst *, 4> Dbgs;
|
|
for (auto &FI : F)
|
|
for (BasicBlock::iterator BI : FI)
|
|
if (auto DDI = dyn_cast<DbgDeclareInst>(BI))
|
|
Dbgs.push_back(DDI);
|
|
|
|
if (Dbgs.empty())
|
|
return false;
|
|
|
|
for (auto &I : Dbgs) {
|
|
DbgDeclareInst *DDI = I;
|
|
AllocaInst *AI = dyn_cast_or_null<AllocaInst>(DDI->getAddress());
|
|
// If this is an alloca for a scalar variable, insert a dbg.value
|
|
// at each load and store to the alloca and erase the dbg.declare.
|
|
// The dbg.values allow tracking a variable even if it is not
|
|
// stored on the stack, while the dbg.declare can only describe
|
|
// the stack slot (and at a lexical-scope granularity). Later
|
|
// passes will attempt to elide the stack slot.
|
|
if (AI && !isArray(AI)) {
|
|
for (User *U : AI->users())
|
|
if (StoreInst *SI = dyn_cast<StoreInst>(U))
|
|
ConvertDebugDeclareToDebugValue(DDI, SI, DIB);
|
|
else if (LoadInst *LI = dyn_cast<LoadInst>(U))
|
|
ConvertDebugDeclareToDebugValue(DDI, LI, DIB);
|
|
else if (CallInst *CI = dyn_cast<CallInst>(U)) {
|
|
// This is a call by-value or some other instruction that
|
|
// takes a pointer to the variable. Insert a *value*
|
|
// intrinsic that describes the alloca.
|
|
auto DbgVal = DIB.insertDbgValueIntrinsic(
|
|
AI, 0, DIVariable(DDI->getVariable()),
|
|
DIExpression(DDI->getExpression()), CI);
|
|
DbgVal->setDebugLoc(DDI->getDebugLoc());
|
|
}
|
|
DDI->eraseFromParent();
|
|
}
|
|
}
|
|
return true;
|
|
}
|
|
|
|
/// FindAllocaDbgDeclare - Finds the llvm.dbg.declare intrinsic describing the
|
|
/// alloca 'V', if any.
|
|
DbgDeclareInst *llvm::FindAllocaDbgDeclare(Value *V) {
|
|
if (auto *L = LocalAsMetadata::getIfExists(V))
|
|
if (auto *MDV = MetadataAsValue::getIfExists(V->getContext(), L))
|
|
for (User *U : MDV->users())
|
|
if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(U))
|
|
return DDI;
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
bool llvm::replaceDbgDeclareForAlloca(AllocaInst *AI, Value *NewAllocaAddress,
|
|
DIBuilder &Builder, bool Deref) {
|
|
DbgDeclareInst *DDI = FindAllocaDbgDeclare(AI);
|
|
if (!DDI)
|
|
return false;
|
|
DebugLoc Loc = DDI->getDebugLoc();
|
|
DIVariable DIVar(DDI->getVariable());
|
|
DIExpression DIExpr(DDI->getExpression());
|
|
assert((!DIVar || DIVar.isVariable()) &&
|
|
"Variable in DbgDeclareInst should be either null or a DIVariable.");
|
|
if (!DIVar)
|
|
return false;
|
|
|
|
if (Deref) {
|
|
// Create a copy of the original DIDescriptor for user variable, prepending
|
|
// "deref" operation to a list of address elements, as new llvm.dbg.declare
|
|
// will take a value storing address of the memory for variable, not
|
|
// alloca itself.
|
|
SmallVector<uint64_t, 4> NewDIExpr;
|
|
NewDIExpr.push_back(dwarf::DW_OP_deref);
|
|
if (DIExpr)
|
|
for (unsigned i = 0, n = DIExpr.getNumElements(); i < n; ++i)
|
|
NewDIExpr.push_back(DIExpr.getElement(i));
|
|
DIExpr = Builder.createExpression(NewDIExpr);
|
|
}
|
|
|
|
// Insert llvm.dbg.declare in the same basic block as the original alloca,
|
|
// and remove old llvm.dbg.declare.
|
|
BasicBlock *BB = AI->getParent();
|
|
Builder.insertDeclare(NewAllocaAddress, DIVar, DIExpr, BB)
|
|
->setDebugLoc(Loc);
|
|
DDI->eraseFromParent();
|
|
return true;
|
|
}
|
|
|
|
/// changeToUnreachable - Insert an unreachable instruction before the specified
|
|
/// instruction, making it and the rest of the code in the block dead.
|
|
static void changeToUnreachable(Instruction *I, bool UseLLVMTrap) {
|
|
BasicBlock *BB = I->getParent();
|
|
// Loop over all of the successors, removing BB's entry from any PHI
|
|
// nodes.
|
|
for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
|
|
(*SI)->removePredecessor(BB);
|
|
|
|
// Insert a call to llvm.trap right before this. This turns the undefined
|
|
// behavior into a hard fail instead of falling through into random code.
|
|
if (UseLLVMTrap) {
|
|
Function *TrapFn =
|
|
Intrinsic::getDeclaration(BB->getParent()->getParent(), Intrinsic::trap);
|
|
CallInst *CallTrap = CallInst::Create(TrapFn, "", I);
|
|
CallTrap->setDebugLoc(I->getDebugLoc());
|
|
}
|
|
new UnreachableInst(I->getContext(), I);
|
|
|
|
// All instructions after this are dead.
|
|
BasicBlock::iterator BBI = I, BBE = BB->end();
|
|
while (BBI != BBE) {
|
|
if (!BBI->use_empty())
|
|
BBI->replaceAllUsesWith(UndefValue::get(BBI->getType()));
|
|
BB->getInstList().erase(BBI++);
|
|
}
|
|
}
|
|
|
|
/// changeToCall - Convert the specified invoke into a normal call.
|
|
static void changeToCall(InvokeInst *II) {
|
|
SmallVector<Value*, 8> Args(II->op_begin(), II->op_end() - 3);
|
|
CallInst *NewCall = CallInst::Create(II->getCalledValue(), Args, "", II);
|
|
NewCall->takeName(II);
|
|
NewCall->setCallingConv(II->getCallingConv());
|
|
NewCall->setAttributes(II->getAttributes());
|
|
NewCall->setDebugLoc(II->getDebugLoc());
|
|
II->replaceAllUsesWith(NewCall);
|
|
|
|
// Follow the call by a branch to the normal destination.
|
|
BranchInst::Create(II->getNormalDest(), II);
|
|
|
|
// Update PHI nodes in the unwind destination
|
|
II->getUnwindDest()->removePredecessor(II->getParent());
|
|
II->eraseFromParent();
|
|
}
|
|
|
|
static bool markAliveBlocks(BasicBlock *BB,
|
|
SmallPtrSetImpl<BasicBlock*> &Reachable) {
|
|
|
|
SmallVector<BasicBlock*, 128> Worklist;
|
|
Worklist.push_back(BB);
|
|
Reachable.insert(BB);
|
|
bool Changed = false;
|
|
do {
|
|
BB = Worklist.pop_back_val();
|
|
|
|
// Do a quick scan of the basic block, turning any obviously unreachable
|
|
// instructions into LLVM unreachable insts. The instruction combining pass
|
|
// canonicalizes unreachable insts into stores to null or undef.
|
|
for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E;++BBI){
|
|
// Assumptions that are known to be false are equivalent to unreachable.
|
|
// Also, if the condition is undefined, then we make the choice most
|
|
// beneficial to the optimizer, and choose that to also be unreachable.
|
|
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(BBI))
|
|
if (II->getIntrinsicID() == Intrinsic::assume) {
|
|
bool MakeUnreachable = false;
|
|
if (isa<UndefValue>(II->getArgOperand(0)))
|
|
MakeUnreachable = true;
|
|
else if (ConstantInt *Cond =
|
|
dyn_cast<ConstantInt>(II->getArgOperand(0)))
|
|
MakeUnreachable = Cond->isZero();
|
|
|
|
if (MakeUnreachable) {
|
|
// Don't insert a call to llvm.trap right before the unreachable.
|
|
changeToUnreachable(BBI, false);
|
|
Changed = true;
|
|
break;
|
|
}
|
|
}
|
|
|
|
if (CallInst *CI = dyn_cast<CallInst>(BBI)) {
|
|
if (CI->doesNotReturn()) {
|
|
// If we found a call to a no-return function, insert an unreachable
|
|
// instruction after it. Make sure there isn't *already* one there
|
|
// though.
|
|
++BBI;
|
|
if (!isa<UnreachableInst>(BBI)) {
|
|
// Don't insert a call to llvm.trap right before the unreachable.
|
|
changeToUnreachable(BBI, false);
|
|
Changed = true;
|
|
}
|
|
break;
|
|
}
|
|
}
|
|
|
|
// Store to undef and store to null are undefined and used to signal that
|
|
// they should be changed to unreachable by passes that can't modify the
|
|
// CFG.
|
|
if (StoreInst *SI = dyn_cast<StoreInst>(BBI)) {
|
|
// Don't touch volatile stores.
|
|
if (SI->isVolatile()) continue;
|
|
|
|
Value *Ptr = SI->getOperand(1);
|
|
|
|
if (isa<UndefValue>(Ptr) ||
|
|
(isa<ConstantPointerNull>(Ptr) &&
|
|
SI->getPointerAddressSpace() == 0)) {
|
|
changeToUnreachable(SI, true);
|
|
Changed = true;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
// Turn invokes that call 'nounwind' functions into ordinary calls.
|
|
if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
|
|
Value *Callee = II->getCalledValue();
|
|
if (isa<ConstantPointerNull>(Callee) || isa<UndefValue>(Callee)) {
|
|
changeToUnreachable(II, true);
|
|
Changed = true;
|
|
} else if (II->doesNotThrow() && canSimplifyInvokeNoUnwind(II)) {
|
|
if (II->use_empty() && II->onlyReadsMemory()) {
|
|
// jump to the normal destination branch.
|
|
BranchInst::Create(II->getNormalDest(), II);
|
|
II->getUnwindDest()->removePredecessor(II->getParent());
|
|
II->eraseFromParent();
|
|
} else
|
|
changeToCall(II);
|
|
Changed = true;
|
|
}
|
|
}
|
|
|
|
Changed |= ConstantFoldTerminator(BB, true);
|
|
for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
|
|
if (Reachable.insert(*SI).second)
|
|
Worklist.push_back(*SI);
|
|
} while (!Worklist.empty());
|
|
return Changed;
|
|
}
|
|
|
|
/// removeUnreachableBlocksFromFn - Remove blocks that are not reachable, even
|
|
/// if they are in a dead cycle. Return true if a change was made, false
|
|
/// otherwise.
|
|
bool llvm::removeUnreachableBlocks(Function &F) {
|
|
SmallPtrSet<BasicBlock*, 128> Reachable;
|
|
bool Changed = markAliveBlocks(F.begin(), Reachable);
|
|
|
|
// If there are unreachable blocks in the CFG...
|
|
if (Reachable.size() == F.size())
|
|
return Changed;
|
|
|
|
assert(Reachable.size() < F.size());
|
|
NumRemoved += F.size()-Reachable.size();
|
|
|
|
// Loop over all of the basic blocks that are not reachable, dropping all of
|
|
// their internal references...
|
|
for (Function::iterator BB = ++F.begin(), E = F.end(); BB != E; ++BB) {
|
|
if (Reachable.count(BB))
|
|
continue;
|
|
|
|
for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
|
|
if (Reachable.count(*SI))
|
|
(*SI)->removePredecessor(BB);
|
|
BB->dropAllReferences();
|
|
}
|
|
|
|
for (Function::iterator I = ++F.begin(); I != F.end();)
|
|
if (!Reachable.count(I))
|
|
I = F.getBasicBlockList().erase(I);
|
|
else
|
|
++I;
|
|
|
|
return true;
|
|
}
|
|
|
|
void llvm::combineMetadata(Instruction *K, const Instruction *J, ArrayRef<unsigned> KnownIDs) {
|
|
SmallVector<std::pair<unsigned, MDNode *>, 4> Metadata;
|
|
K->dropUnknownMetadata(KnownIDs);
|
|
K->getAllMetadataOtherThanDebugLoc(Metadata);
|
|
for (unsigned i = 0, n = Metadata.size(); i < n; ++i) {
|
|
unsigned Kind = Metadata[i].first;
|
|
MDNode *JMD = J->getMetadata(Kind);
|
|
MDNode *KMD = Metadata[i].second;
|
|
|
|
switch (Kind) {
|
|
default:
|
|
K->setMetadata(Kind, nullptr); // Remove unknown metadata
|
|
break;
|
|
case LLVMContext::MD_dbg:
|
|
llvm_unreachable("getAllMetadataOtherThanDebugLoc returned a MD_dbg");
|
|
case LLVMContext::MD_tbaa:
|
|
K->setMetadata(Kind, MDNode::getMostGenericTBAA(JMD, KMD));
|
|
break;
|
|
case LLVMContext::MD_alias_scope:
|
|
K->setMetadata(Kind, MDNode::getMostGenericAliasScope(JMD, KMD));
|
|
break;
|
|
case LLVMContext::MD_noalias:
|
|
K->setMetadata(Kind, MDNode::intersect(JMD, KMD));
|
|
break;
|
|
case LLVMContext::MD_range:
|
|
K->setMetadata(Kind, MDNode::getMostGenericRange(JMD, KMD));
|
|
break;
|
|
case LLVMContext::MD_fpmath:
|
|
K->setMetadata(Kind, MDNode::getMostGenericFPMath(JMD, KMD));
|
|
break;
|
|
case LLVMContext::MD_invariant_load:
|
|
// Only set the !invariant.load if it is present in both instructions.
|
|
K->setMetadata(Kind, JMD);
|
|
break;
|
|
case LLVMContext::MD_nonnull:
|
|
// Only set the !nonnull if it is present in both instructions.
|
|
K->setMetadata(Kind, JMD);
|
|
break;
|
|
}
|
|
}
|
|
}
|