================ @@ -0,0 +1,341 @@ +//===- ControlFlowUtils.cpp - Control Flow Utilities -----------------------==// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// +// +// Utilities to manipulate the CFG and restore SSA for the new control flow. +// +//===----------------------------------------------------------------------===// + +#include "llvm/Transforms/Utils/ControlFlowUtils.h" +#include "llvm/ADT/SetVector.h" +#include "llvm/ADT/SmallSet.h" +#include "llvm/Analysis/DomTreeUpdater.h" +#include "llvm/IR/Constants.h" +#include "llvm/IR/Instructions.h" +#include "llvm/IR/ValueHandle.h" +#include "llvm/Transforms/Utils/Local.h" + +#define DEBUG_TYPE "control-flow-hub" + +using namespace llvm; + +using BBPredicates = DenseMap<BasicBlock *, Instruction *>; +using EdgeDescriptor = ControlFlowHub::BranchDescriptor; + +// Redirects the terminator of the incoming block to the first guard block in +// the hub. Returns the branch condition from `BB` if it exits. +// - If only one of Succ0 or Succ1 is not null, the corresponding branch +// successor is redirected to the FirstGuardBlock. +// - Else both are not null, and branch is replaced with an unconditional +// branch to the FirstGuardBlock. +static Value *redirectToHub(BasicBlock *BB, BasicBlock *Succ0, + BasicBlock *Succ1, BasicBlock *FirstGuardBlock) { + assert(isa<BranchInst>(BB->getTerminator()) && + "Only support branch terminator."); + auto *Branch = cast<BranchInst>(BB->getTerminator()); + auto *Condition = Branch->isConditional() ? Branch->getCondition() : nullptr; + + assert(Succ0 || Succ1); + + if (Branch->isUnconditional()) { + assert(Succ0 == Branch->getSuccessor(0)); + assert(!Succ1); + Branch->setSuccessor(0, FirstGuardBlock); + } else { + assert(!Succ1 || Succ1 == Branch->getSuccessor(1)); + if (Succ0 && !Succ1) { + Branch->setSuccessor(0, FirstGuardBlock); + } else if (Succ1 && !Succ0) { + Branch->setSuccessor(1, FirstGuardBlock); + } else { + Branch->eraseFromParent(); + BranchInst::Create(FirstGuardBlock, BB); + } + } + + return Condition; +} + +// Setup the branch instructions for guard blocks. +// +// Each guard block terminates in a conditional branch that transfers +// control to the corresponding outgoing block or the next guard +// block. The last guard block has two outgoing blocks as successors. +static void setupBranchForGuard(ArrayRef<BasicBlock *> GuardBlocks, + ArrayRef<BasicBlock *> Outgoing, + BBPredicates &GuardPredicates) { + assert(Outgoing.size() > 1); + assert(GuardBlocks.size() == Outgoing.size() - 1); + int I = 0; + for (int E = GuardBlocks.size() - 1; I != E; ++I) { + BasicBlock *Out = Outgoing[I]; + BranchInst::Create(Out, GuardBlocks[I + 1], GuardPredicates[Out], + GuardBlocks[I]); + } + BasicBlock *Out = Outgoing[I]; + BranchInst::Create(Out, Outgoing[I + 1], GuardPredicates[Out], + GuardBlocks[I]); +} + +// Assign an index to each outgoing block. At the corresponding guard +// block, compute the branch condition by comparing this index. +static void calcPredicateUsingInteger(ArrayRef<EdgeDescriptor> Branches, + ArrayRef<BasicBlock *> Outgoing, + ArrayRef<BasicBlock *> GuardBlocks, + BBPredicates &GuardPredicates) { + LLVMContext &Context = GuardBlocks.front()->getContext(); + BasicBlock *FirstGuardBlock = GuardBlocks.front(); + + auto *Phi = PHINode::Create(Type::getInt32Ty(Context), Branches.size(), + "merged.bb.idx", FirstGuardBlock); + + for (auto [BB, Succ0, Succ1] : Branches) { + Value *Condition = redirectToHub(BB, Succ0, Succ1, FirstGuardBlock); + Value *IncomingId = nullptr; + if (Succ0 && Succ1) { + auto Succ0Iter = find(Outgoing, Succ0); + auto Succ1Iter = find(Outgoing, Succ1); + Value *Id0 = ConstantInt::get(Type::getInt32Ty(Context), + std::distance(Outgoing.begin(), Succ0Iter)); + Value *Id1 = ConstantInt::get(Type::getInt32Ty(Context), ---------------- arsenm wrote:
Avoid repeated getInt32Ty calls https://github.com/llvm/llvm-project/pull/103013 _______________________________________________ llvm-branch-commits mailing list llvm-branch-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
