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Introduce fix-irreducible pass

An irreducible SCC is one which has multiple "header" blocks, i.e., blocks
with control-flow edges incident from outside the SCC. This pass converts an
irreducible SCC into a natural loop by introducing a single new header
block and redirecting all the edges on the original headers to this
new block.

This is a useful workaround for a limitation in the structurizer
which, which produces incorrect control flow in the presence of
irreducible regions. The AMDGPU backend provides an option to
enable this pass before the structurizer, which may eventually be
enabled by default.

Reviewed By: nhaehnle

Differential Revision: https://reviews.llvm.org/D77198

This restores commit 2ada8e2525dd2653f30c8696a27162a3b1647d66.

Originally reverted with commit 44e09b59b869a91bf47d76e8bc569d9ee91ad145.
This commit is contained in:
Sameer Sahasrabuddhe 2020-04-15 15:05:51 +05:30
parent a878613498
commit ba6d13ef23
14 changed files with 1403 additions and 38 deletions

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@ -962,6 +962,12 @@ public:
return L && L->getHeader() == BB;
}
/// Return the top-level loops.
const std::vector<LoopT *> &getTopLevelLoops() const { return TopLevelLoops; }
/// Return the top-level loops.
std::vector<LoopT *> &getTopLevelLoopsVector() { return TopLevelLoops; }
/// This removes the specified top-level loop from this loop info object.
/// The loop is not deleted, as it will presumably be inserted into
/// another loop.

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@ -152,6 +152,7 @@ void initializeExternalAAWrapperPassPass(PassRegistry&);
void initializeFEntryInserterPass(PassRegistry&);
void initializeFinalizeISelPass(PassRegistry&);
void initializeFinalizeMachineBundlesPass(PassRegistry&);
void initializeFixIrreduciblePass(PassRegistry &);
void initializeFixupStatepointCallerSavedPass(PassRegistry&);
void initializeFlattenCFGPassPass(PassRegistry&);
void initializeFloat2IntLegacyPassPass(PassRegistry&);

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@ -231,6 +231,7 @@ namespace {
(void) llvm::createHardwareLoopsPass();
(void) llvm::createInjectTLIMappingsLegacyPass();
(void) llvm::createUnifyLoopExitsPass();
(void) llvm::createFixIrreduciblePass();
(void)new llvm::IntervalPartition();
(void)new llvm::ScalarEvolutionWrapperPass();

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@ -134,6 +134,13 @@ FunctionPass *createInjectTLIMappingsLegacyPass();
// exit blocks.
//
FunctionPass *createUnifyLoopExitsPass();
//===----------------------------------------------------------------------===//
//
// FixIrreducible - Convert each SCC with irreducible control-flow
// into a natural loop.
//
FunctionPass *createFixIrreduciblePass();
}
#endif

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@ -864,6 +864,7 @@ bool GCNPassConfig::addPreISel() {
addPass(&AMDGPUUnifyDivergentExitNodesID);
if (!LateCFGStructurize) {
if (EnableStructurizerWorkarounds) {
addPass(createFixIrreduciblePass());
addPass(createUnifyLoopExitsPass());
}
addPass(createStructurizeCFGPass(false)); // true -> SkipUniformRegions

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@ -1144,18 +1144,62 @@ static void reconnectPhis(BasicBlock *Out, BasicBlock *GuardBlock,
using BBPredicates = DenseMap<BasicBlock *, PHINode *>;
using BBSetVector = SetVector<BasicBlock *>;
// Collect predicates for each outgoing block. If control reaches the
// Hub from an incoming block InBB, then the predicate for each
// outgoing block OutBB decides whether control is forwarded to OutBB.
// Redirects the terminator of the incoming block to the first guard
// block in the hub. The condition of the original terminator (if it
// was conditional) and its original successors are returned as a
// tuple <condition, succ0, succ1>. The function additionally filters
// out successors that are not in the set of outgoing blocks.
//
// These predicates are not orthogonal. The Hub evaluates them in the
// same order as the Outgoing set-vector, and control branches to the
// first outgoing block whose predicate evaluates to true.
static void createGuardPredicates(BasicBlock *FirstGuardBlock,
BBPredicates &GuardPredicates,
SmallVectorImpl<WeakVH> &DeletionCandidates,
const BBSetVector &Incoming,
const BBSetVector &Outgoing) {
// - condition is non-null iff the branch is conditional.
// - Succ1 is non-null iff the sole/taken target is an outgoing block.
// - Succ2 is non-null iff condition is non-null and the fallthrough
// target is an outgoing block.
static std::tuple<Value *, BasicBlock *, BasicBlock *>
redirectToHub(BasicBlock *BB, BasicBlock *FirstGuardBlock,
const BBSetVector &Outgoing) {
auto Branch = cast<BranchInst>(BB->getTerminator());
auto Condition = Branch->isConditional() ? Branch->getCondition() : nullptr;
BasicBlock *Succ0 = Branch->getSuccessor(0);
BasicBlock *Succ1 = nullptr;
Succ0 = Outgoing.count(Succ0) ? Succ0 : nullptr;
if (Branch->isUnconditional()) {
Branch->setSuccessor(0, FirstGuardBlock);
assert(Succ0);
} else {
Succ1 = Branch->getSuccessor(1);
Succ1 = Outgoing.count(Succ1) ? Succ1 : nullptr;
assert(Succ0 || Succ1);
if (Succ0 && !Succ1) {
Branch->setSuccessor(0, FirstGuardBlock);
} else if (Succ1 && !Succ0) {
Branch->setSuccessor(1, FirstGuardBlock);
} else {
Branch->eraseFromParent();
BranchInst::Create(FirstGuardBlock, BB);
}
}
assert(Succ0 || Succ1);
return std::make_tuple(Condition, Succ0, Succ1);
}
// Capture the existing control flow as guard predicates, and redirect
// control flow from every incoming block to the first guard block in
// the hub.
//
// There is one guard predicate for each outgoing block OutBB. The
// predicate is a PHINode with one input for each InBB which
// represents whether the hub should transfer control flow to OutBB if
// it arrived from InBB. These predicates are NOT ORTHOGONAL. The Hub
// evaluates them in the same order as the Outgoing set-vector, and
// control branches to the first outgoing block whose predicate
// evaluates to true.
static void convertToGuardPredicates(
BasicBlock *FirstGuardBlock, BBPredicates &GuardPredicates,
SmallVectorImpl<WeakVH> &DeletionCandidates, const BBSetVector &Incoming,
const BBSetVector &Outgoing) {
auto &Context = Incoming.front()->getContext();
auto BoolTrue = ConstantInt::getTrue(Context);
auto BoolFalse = ConstantInt::getFalse(Context);
@ -1172,30 +1216,11 @@ static void createGuardPredicates(BasicBlock *FirstGuardBlock,
}
for (auto In : Incoming) {
auto Branch = cast<BranchInst>(In->getTerminator());
BasicBlock *Succ0 = Branch->getSuccessor(0);
BasicBlock *Succ1 = nullptr;
Succ0 = Outgoing.count(Succ0) ? Succ0 : nullptr;
if (Branch->isUnconditional()) {
Branch->setSuccessor(0, FirstGuardBlock);
assert(Succ0);
} else {
Succ1 = Branch->getSuccessor(1);
Succ1 = Outgoing.count(Succ1) ? Succ1 : nullptr;
assert(Succ0 || Succ1);
if (Succ0 && !Succ1) {
Branch->setSuccessor(0, FirstGuardBlock);
} else if (Succ1 && !Succ0) {
Branch->setSuccessor(1, FirstGuardBlock);
} else {
Branch->eraseFromParent();
BranchInst::Create(FirstGuardBlock, In);
}
}
assert(Succ0 || Succ1);
Value *Condition;
BasicBlock *Succ0;
BasicBlock *Succ1;
std::tie(Condition, Succ0, Succ1) =
redirectToHub(In, FirstGuardBlock, Outgoing);
// Optimization: Consider an incoming block A with both successors
// Succ0 and Succ1 in the set of outgoing blocks. The predicates
@ -1205,7 +1230,6 @@ static void createGuardPredicates(BasicBlock *FirstGuardBlock,
// control must reach Succ1, which means that the predicate for
// Succ1 is always true.
bool OneSuccessorDone = false;
auto Condition = Branch->getCondition();
for (int i = 0, e = Outgoing.size() - 1; i != e; ++i) {
auto Out = Outgoing[i];
auto Phi = GuardPredicates[Out];
@ -1287,8 +1311,8 @@ BasicBlock *llvm::CreateControlFlowHub(
BBPredicates GuardPredicates;
SmallVector<WeakVH, 8> DeletionCandidates;
createGuardPredicates(FirstGuardBlock, GuardPredicates, DeletionCandidates,
Incoming, Outgoing);
convertToGuardPredicates(FirstGuardBlock, GuardPredicates, DeletionCandidates,
Incoming, Outgoing);
GuardBlocks.push_back(FirstGuardBlock);
createGuardBlocks(GuardBlocks, F, Outgoing, GuardPredicates, Prefix);

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@ -20,6 +20,7 @@ add_llvm_component_library(LLVMTransformUtils
EntryExitInstrumenter.cpp
EscapeEnumerator.cpp
Evaluator.cpp
FixIrreducible.cpp
FlattenCFG.cpp
FunctionComparator.cpp
FunctionImportUtils.cpp

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@ -0,0 +1,333 @@
//===- FixIrreducible.cpp - Convert irreducible control-flow into loops ---===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// An irreducible SCC is one which has multiple "header" blocks, i.e., blocks
// with control-flow edges incident from outside the SCC. This pass converts a
// irreducible SCC into a natural loop by applying the following transformation:
//
// 1. Collect the set of headers H of the SCC.
// 2. Collect the set of predecessors P of these headers. These may be inside as
// well as outside the SCC.
// 3. Create block N and redirect every edge from set P to set H through N.
//
// This converts the SCC into a natural loop with N as the header: N is the only
// block with edges incident from outside the SCC, and all backedges in the SCC
// are incident on N, i.e., for every backedge, the head now dominates the tail.
//
// INPUT CFG: The blocks A and B form an irreducible loop with two headers.
//
// Entry
// / \
// v v
// A ----> B
// ^ /|
// `----' |
// v
// Exit
//
// OUTPUT CFG: Edges incident on A and B are now redirected through a
// new block N, forming a natural loop consisting of N, A and B.
//
// Entry
// |
// v
// .---> N <---.
// / / \ \
// | / \ |
// \ v v /
// `-- A B --'
// |
// v
// Exit
//
// The transformation is applied to every maximal SCC that is not already
// recognized as a loop. The pass operates on all maximal SCCs found in the
// function body outside of any loop, as well as those found inside each loop,
// including inside any newly created loops. This ensures that any SCC hidden
// inside a maximal SCC is also transformed.
//
// The actual transformation is handled by function CreateControlFlowHub, which
// takes a set of incoming blocks (the predecessors) and outgoing blocks (the
// headers). The function also moves every PHINode in an outgoing block to the
// hub. Since the hub dominates all the outgoing blocks, each such PHINode
// continues to dominate its uses. Since every header in an SCC has at least two
// predecessors, every value used in the header (or later) but defined in a
// predecessor (or earlier) is represented by a PHINode in a header. Hence the
// above handling of PHINodes is sufficient and no further processing is
// required to restore SSA.
//
// Limitation: The pass cannot handle switch statements and indirect
// branches. Both must be lowered to plain branches first.
//
//===----------------------------------------------------------------------===//
#include "llvm/ADT/SCCIterator.h"
#include "llvm/Analysis/LoopIterator.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/Transforms/Utils.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#define DEBUG_TYPE "fix-irreducible"
using namespace llvm;
namespace {
struct FixIrreducible : public FunctionPass {
static char ID;
FixIrreducible() : FunctionPass(ID) {
initializeFixIrreduciblePass(*PassRegistry::getPassRegistry());
}
void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequiredID(LowerSwitchID);
AU.addRequired<DominatorTreeWrapperPass>();
AU.addRequired<LoopInfoWrapperPass>();
AU.addPreservedID(LowerSwitchID);
AU.addPreserved<DominatorTreeWrapperPass>();
AU.addPreserved<LoopInfoWrapperPass>();
}
bool runOnFunction(Function &F);
};
} // namespace
char FixIrreducible::ID = 0;
FunctionPass *llvm::createFixIrreduciblePass() { return new FixIrreducible(); }
INITIALIZE_PASS_BEGIN(FixIrreducible, "fix-irreducible",
"Convert irreducible control-flow into natural loops",
false /* Only looks at CFG */, false /* Analysis Pass */)
INITIALIZE_PASS_DEPENDENCY(LowerSwitch)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
INITIALIZE_PASS_END(FixIrreducible, "fix-irreducible",
"Convert irreducible control-flow into natural loops",
false /* Only looks at CFG */, false /* Analysis Pass */)
// When a new loop is created, existing children of the parent loop may now be
// fully inside the new loop. Reconnect these as children of the new loop.
static void reconnectChildLoops(LoopInfo &LI, Loop *ParentLoop, Loop *NewLoop,
SetVector<BasicBlock *> &Blocks,
SetVector<BasicBlock *> &Headers) {
auto &CandidateLoops = ParentLoop ? ParentLoop->getSubLoopsVector()
: LI.getTopLevelLoopsVector();
// Partition the candidate loops into two ranges. The first part
// contains loops that are not children of the new loop. The second
// part contains children that need to be moved to the new loop.
auto FirstChild =
std::partition(CandidateLoops.begin(), CandidateLoops.end(), [&](Loop *L) {
return L == NewLoop || Blocks.count(L->getHeader()) == 0;
});
for (auto II = FirstChild, IE = CandidateLoops.end(); II != IE; ++II) {
auto Child = *II;
LLVM_DEBUG(dbgs() << "child loop: " << Child->getHeader()->getName()
<< "\n");
// TODO: A child loop whose header is also a header in the current
// SCC gets destroyed since its backedges are removed. That may
// not be necessary if we can retain such backedges.
if (Headers.count(Child->getHeader())) {
for (auto BB : Child->blocks()) {
LI.changeLoopFor(BB, NewLoop);
LLVM_DEBUG(dbgs() << "moved block from child: " << BB->getName()
<< "\n");
}
LI.destroy(Child);
LLVM_DEBUG(dbgs() << "subsumed child loop (common header)\n");
continue;
}
if (ParentLoop) {
LLVM_DEBUG(dbgs() << "removed child loop from parent\n");
ParentLoop->removeChildLoop(Child);
}
LLVM_DEBUG(dbgs() << "added child loop to new loop\n");
NewLoop->addChildLoop(Child);
}
CandidateLoops.erase(FirstChild, CandidateLoops.end());
}
// Given a set of blocks and headers in an irreducible SCC, convert it into a
// natural loop. Also insert this new loop at its appropriate place in the
// hierarchy of loops.
static void createNaturalLoopInternal(LoopInfo &LI, DominatorTree &DT,
Loop *ParentLoop,
SetVector<BasicBlock *> &Blocks,
SetVector<BasicBlock *> &Headers) {
#ifndef NDEBUG
// All headers are part of the SCC
for (auto H : Headers) {
assert(Blocks.count(H));
}
#endif
SetVector<BasicBlock *> Predecessors;
for (auto H : Headers) {
for (auto P : predecessors(H)) {
Predecessors.insert(P);
}
}
LLVM_DEBUG(
dbgs() << "Found predecessors:";
for (auto P : Predecessors) {
dbgs() << " " << P->getName();
}
dbgs() << "\n");
// Redirect all the backedges through a "hub" consisting of a series
// of guard blocks that manage the flow of control from the
// predecessors to the headers.
SmallVector<BasicBlock *, 8> GuardBlocks;
DomTreeUpdater DTU(DT, DomTreeUpdater::UpdateStrategy::Eager);
CreateControlFlowHub(&DTU, GuardBlocks, Predecessors, Headers, "irr");
#if defined(EXPENSIVE_CHECKS)
assert(DT.verify(DominatorTree::VerificationLevel::Full));
#else
assert(DT.verify(DominatorTree::VerificationLevel::Fast));
#endif
// Create a new loop from the now-transformed cycle
auto NewLoop = LI.AllocateLoop();
if (ParentLoop) {
ParentLoop->addChildLoop(NewLoop);
} else {
LI.addTopLevelLoop(NewLoop);
}
// Add the guard blocks to the new loop. The first guard block is
// the head of all the backedges, and it is the first to be inserted
// in the loop. This ensures that it is recognized as the
// header. Since the new loop is already in LoopInfo, the new blocks
// are also propagated up the chain of parent loops.
for (auto G : GuardBlocks) {
LLVM_DEBUG(dbgs() << "added guard block: " << G->getName() << "\n");
NewLoop->addBasicBlockToLoop(G, LI);
}
// Add the SCC blocks to the new loop.
for (auto BB : Blocks) {
NewLoop->addBlockEntry(BB);
if (LI.getLoopFor(BB) == ParentLoop) {
LLVM_DEBUG(dbgs() << "moved block from parent: " << BB->getName()
<< "\n");
LI.changeLoopFor(BB, NewLoop);
} else {
LLVM_DEBUG(dbgs() << "added block from child: " << BB->getName() << "\n");
}
}
LLVM_DEBUG(dbgs() << "header for new loop: "
<< NewLoop->getHeader()->getName() << "\n");
reconnectChildLoops(LI, ParentLoop, NewLoop, Blocks, Headers);
NewLoop->verifyLoop();
if (ParentLoop) {
ParentLoop->verifyLoop();
}
#if defined(EXPENSIVE_CHECKS)
LI.verify(DT);
#endif // EXPENSIVE_CHECKS
}
// Enable the graph traits required for traversing a Loop body.
template <> struct llvm::GraphTraits<Loop> : LoopBodyTraits {};
// Overloaded wrappers to go with the function template below.
BasicBlock *unwrapBlock(BasicBlock *B) { return B; }
BasicBlock *unwrapBlock(LoopBodyTraits::NodeRef &N) { return N.second; }
static void createNaturalLoop(LoopInfo &LI, DominatorTree &DT, Function *F,
SetVector<BasicBlock *> &Blocks,
SetVector<BasicBlock *> &Headers) {
createNaturalLoopInternal(LI, DT, nullptr, Blocks, Headers);
}
static void createNaturalLoop(LoopInfo &LI, DominatorTree &DT, Loop &L,
SetVector<BasicBlock *> &Blocks,
SetVector<BasicBlock *> &Headers) {
createNaturalLoopInternal(LI, DT, &L, Blocks, Headers);
}
// Convert irreducible SCCs; Graph G may be a Function* or a Loop&.
template <class Graph>
static bool makeReducible(LoopInfo &LI, DominatorTree &DT, Graph &&G) {
bool Changed = false;
for (auto Scc = scc_begin(G); !Scc.isAtEnd(); ++Scc) {
if (Scc->size() < 2)
continue;
SetVector<BasicBlock *> Blocks;
LLVM_DEBUG(dbgs() << "Found SCC:");
for (auto N : *Scc) {
auto BB = unwrapBlock(N);
LLVM_DEBUG(dbgs() << " " << BB->getName());
Blocks.insert(BB);
}
LLVM_DEBUG(dbgs() << "\n");
// Minor optimization: The SCC blocks are usually discovered in an order
// that is the opposite of the order in which these blocks appear as branch
// targets. This results in a lot of condition inversions in the control
// flow out of the new ControlFlowHub, which can be mitigated if the orders
// match. So we discover the headers using the reverse of the block order.
SetVector<BasicBlock *> Headers;
LLVM_DEBUG(dbgs() << "Found headers:");
for (auto BB : reverse(Blocks)) {
for (const auto P : predecessors(BB)) {
if (!Blocks.count(P)) {
LLVM_DEBUG(dbgs() << " " << BB->getName());
Headers.insert(BB);
break;
}
}
}
LLVM_DEBUG(dbgs() << "\n");
if (Headers.size() == 1) {
assert(LI.isLoopHeader(Headers.front()));
LLVM_DEBUG(dbgs() << "Natural loop with a single header: skipped\n");
continue;
}
createNaturalLoop(LI, DT, G, Blocks, Headers);
Changed = true;
}
return Changed;
}
bool FixIrreducible::runOnFunction(Function &F) {
LLVM_DEBUG(dbgs() << "===== Fix irreducible control-flow in function: "
<< F.getName() << "\n");
auto &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
bool Changed = false;
SmallVector<Loop *, 8> WorkList;
LLVM_DEBUG(dbgs() << "visiting top-level\n");
Changed |= makeReducible(LI, DT, &F);
// Any SCCs reduced are now already in the list of top-level loops, so simply
// add them all to the worklist.
for (auto L : LI) {
WorkList.push_back(L);
}
while (!WorkList.empty()) {
auto L = WorkList.back();
WorkList.pop_back();
LLVM_DEBUG(dbgs() << "visiting loop with header "
<< L->getHeader()->getName() << "\n");
Changed |= makeReducible(LI, DT, *L);
// Any SCCs reduced are now already in the list of child loops, so simply
// add them all to the worklist.
WorkList.append(L->begin(), L->end());
}
return Changed;
}

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@ -40,6 +40,7 @@ void llvm::initializeTransformUtils(PassRegistry &Registry) {
initializeStripGCRelocatesPass(Registry);
initializePredicateInfoPrinterLegacyPassPass(Registry);
initializeInjectTLIMappingsLegacyPass(Registry);
initializeFixIrreduciblePass(Registry);
initializeUnifyLoopExitsPass(Registry);
}

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@ -0,0 +1,268 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -fix-irreducible -S | FileCheck %s -check-prefix=CHECK
define i32 @basic(i1 %PredEntry, i1 %PredLeft, i1 %PredRight, i32 %X, i32 %Y) {
; CHECK-LABEL: @basic(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[IRR_GUARD:%.*]]
; CHECK: left:
; CHECK-NEXT: [[L:%.*]] = add i32 [[L_PHI_MOVED:%.*]], 1
; CHECK-NEXT: br i1 [[PREDLEFT:%.*]], label [[IRR_GUARD]], label [[EXIT:%.*]]
; CHECK: right:
; CHECK-NEXT: br i1 [[PREDRIGHT:%.*]], label [[IRR_GUARD]], label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: [[Z:%.*]] = phi i32 [ [[L]], [[LEFT:%.*]] ], [ [[R_PHI_MOVED:%.*]], [[RIGHT:%.*]] ]
; CHECK-NEXT: ret i32 [[Z]]
; CHECK: irr.guard:
; CHECK-NEXT: [[GUARD_LEFT:%.*]] = phi i1 [ true, [[RIGHT]] ], [ [[PREDENTRY:%.*]], [[ENTRY:%.*]] ], [ false, [[LEFT]] ]
; CHECK-NEXT: [[L_PHI_MOVED]] = phi i32 [ [[R_PHI_MOVED]], [[RIGHT]] ], [ [[X:%.*]], [[ENTRY]] ], [ [[L_PHI_MOVED]], [[LEFT]] ]
; CHECK-NEXT: [[R_PHI_MOVED]] = phi i32 [ [[R_PHI_MOVED]], [[RIGHT]] ], [ [[Y:%.*]], [[ENTRY]] ], [ [[L]], [[LEFT]] ]
; CHECK-NEXT: br i1 [[GUARD_LEFT]], label [[LEFT]], label [[RIGHT]]
;
entry:
br i1 %PredEntry, label %left, label %right
left:
%L.phi = phi i32 [%X, %entry], [%R.phi, %right]
%L = add i32 %L.phi, 1
br i1 %PredLeft, label %right, label %exit
right:
%R.phi = phi i32 [%Y, %entry], [%L, %left]
br i1 %PredRight, label %left, label %exit
exit:
%Z = phi i32 [%L, %left], [%R.phi, %right]
ret i32 %Z
}
define i32 @feedback_loop(i1 %PredEntry, i1 %PredLeft, i1 %PredRight, i32 %X, i32 %Y) {
; CHECK-LABEL: @feedback_loop(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[IRR_GUARD:%.*]]
; CHECK: left:
; CHECK-NEXT: br i1 [[PREDLEFT:%.*]], label [[IRR_GUARD]], label [[EXIT:%.*]]
; CHECK: right:
; CHECK-NEXT: br i1 [[PREDRIGHT:%.*]], label [[IRR_GUARD]], label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: [[Z:%.*]] = phi i32 [ [[L_PHI_MOVED:%.*]], [[LEFT:%.*]] ], [ [[R_PHI_MOVED:%.*]], [[RIGHT:%.*]] ]
; CHECK-NEXT: ret i32 [[Z]]
; CHECK: irr.guard:
; CHECK-NEXT: [[GUARD_LEFT:%.*]] = phi i1 [ true, [[RIGHT]] ], [ [[PREDENTRY:%.*]], [[ENTRY:%.*]] ], [ false, [[LEFT]] ]
; CHECK-NEXT: [[L_PHI_MOVED]] = phi i32 [ [[R_PHI_MOVED]], [[RIGHT]] ], [ [[X:%.*]], [[ENTRY]] ], [ [[L_PHI_MOVED]], [[LEFT]] ]
; CHECK-NEXT: [[R_PHI_MOVED]] = phi i32 [ [[R_PHI_MOVED]], [[RIGHT]] ], [ [[Y:%.*]], [[ENTRY]] ], [ [[L_PHI_MOVED]], [[LEFT]] ]
; CHECK-NEXT: br i1 [[GUARD_LEFT]], label [[LEFT]], label [[RIGHT]]
;
entry:
br i1 %PredEntry, label %left, label %right
left:
%L.phi = phi i32 [%X, %entry], [%R.phi, %right]
br i1 %PredLeft, label %right, label %exit
right:
%R.phi = phi i32 [%Y, %entry], [%L.phi, %left]
br i1 %PredRight, label %left, label %exit
exit:
%Z = phi i32 [%L.phi, %left], [%R.phi, %right]
ret i32 %Z
}
define i32 @multiple_predecessors(i1 %PredEntry, i1 %PredA, i1 %PredB, i1 %PredC, i1 %PredD, i32 %X, i32 %Y) {
; CHECK-LABEL: @multiple_predecessors(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[PREDB_INV:%.*]] = xor i1 [[PREDB:%.*]], true
; CHECK-NEXT: br i1 [[PREDENTRY:%.*]], label [[A:%.*]], label [[B:%.*]]
; CHECK: A:
; CHECK-NEXT: [[A_INC:%.*]] = add i32 [[X:%.*]], 1
; CHECK-NEXT: br label [[IRR_GUARD:%.*]]
; CHECK: B:
; CHECK-NEXT: br label [[IRR_GUARD]]
; CHECK: C:
; CHECK-NEXT: br i1 [[PREDC:%.*]], label [[IRR_GUARD]], label [[EXIT:%.*]]
; CHECK: D:
; CHECK-NEXT: [[D_INC:%.*]] = add i32 [[D_PHI_MOVED:%.*]], 1
; CHECK-NEXT: br i1 [[PREDD:%.*]], label [[EXIT]], label [[IRR_GUARD]]
; CHECK: exit:
; CHECK-NEXT: [[RET:%.*]] = phi i32 [ [[C_PHI_MOVED:%.*]], [[C:%.*]] ], [ [[D_INC]], [[D:%.*]] ]
; CHECK-NEXT: ret i32 [[RET]]
; CHECK: irr.guard:
; CHECK-NEXT: [[GUARD_C:%.*]] = phi i1 [ true, [[D]] ], [ [[PREDB_INV]], [[B]] ], [ [[PREDA:%.*]], [[A]] ], [ false, [[C]] ]
; CHECK-NEXT: [[C_PHI_MOVED]] = phi i32 [ [[D_INC]], [[D]] ], [ [[Y:%.*]], [[B]] ], [ [[X]], [[A]] ], [ [[C_PHI_MOVED]], [[C]] ]
; CHECK-NEXT: [[D_PHI_MOVED]] = phi i32 [ [[D_PHI_MOVED]], [[D]] ], [ [[Y]], [[B]] ], [ [[A_INC]], [[A]] ], [ [[C_PHI_MOVED]], [[C]] ]
; CHECK-NEXT: br i1 [[GUARD_C]], label [[C]], label [[D]]
;
entry:
br i1 %PredEntry, label %A, label %B
A:
%A.inc = add i32 %X, 1
br i1 %PredA, label %C, label %D
B:
br i1 %PredB, label %D, label %C
C:
%C.phi = phi i32 [%X, %A], [%Y, %B], [%D.inc, %D]
br i1 %PredC, label %D, label %exit
D:
%D.phi = phi i32 [%A.inc, %A], [%Y, %B], [%C.phi, %C]
%D.inc = add i32 %D.phi, 1
br i1 %PredD, label %exit, label %C
exit:
%ret = phi i32 [%C.phi, %C], [%D.inc, %D]
ret i32 %ret
}
define i32 @separate_predecessors(i1 %PredEntry, i1 %PredA, i1 %PredB, i1 %PredC, i1 %PredD, i32 %X, i32 %Y) {
; CHECK-LABEL: @separate_predecessors(
; CHECK-NEXT: entry:
; CHECK-NEXT: br i1 [[PREDENTRY:%.*]], label [[A:%.*]], label [[B:%.*]]
; CHECK: A:
; CHECK-NEXT: [[A_INC:%.*]] = add i32 [[X:%.*]], 1
; CHECK-NEXT: br label [[IRR_GUARD:%.*]]
; CHECK: B:
; CHECK-NEXT: br label [[IRR_GUARD]]
; CHECK: C:
; CHECK-NEXT: br i1 [[PREDC:%.*]], label [[EXIT:%.*]], label [[IRR_GUARD]]
; CHECK: D:
; CHECK-NEXT: [[D_INC:%.*]] = add i32 [[D_PHI_MOVED:%.*]], 1
; CHECK-NEXT: br i1 [[PREDD:%.*]], label [[EXIT]], label [[IRR_GUARD]]
; CHECK: exit:
; CHECK-NEXT: [[RET:%.*]] = phi i32 [ [[C_PHI_MOVED:%.*]], [[C:%.*]] ], [ [[D_INC]], [[D:%.*]] ]
; CHECK-NEXT: ret i32 [[RET]]
; CHECK: irr.guard:
; CHECK-NEXT: [[GUARD_C:%.*]] = phi i1 [ true, [[D]] ], [ true, [[A]] ], [ false, [[C]] ], [ false, [[B]] ]
; CHECK-NEXT: [[C_PHI_MOVED]] = phi i32 [ [[D_INC]], [[D]] ], [ [[X]], [[A]] ], [ [[C_PHI_MOVED]], [[C]] ], [ undef, [[B]] ]
; CHECK-NEXT: [[D_PHI_MOVED]] = phi i32 [ [[D_PHI_MOVED]], [[D]] ], [ undef, [[A]] ], [ [[C_PHI_MOVED]], [[C]] ], [ [[Y:%.*]], [[B]] ]
; CHECK-NEXT: br i1 [[GUARD_C]], label [[C]], label [[D]]
;
entry:
br i1 %PredEntry, label %A, label %B
A:
%A.inc = add i32 %X, 1
br label %C
B:
br label %D
C:
%C.phi = phi i32 [%X, %A], [%D.inc, %D]
br i1 %PredC, label %exit, label %D
D:
%D.phi = phi i32 [%Y, %B], [%C.phi, %C]
%D.inc = add i32 %D.phi, 1
br i1 %PredD, label %exit, label %C
exit:
%ret = phi i32 [%C.phi, %C], [%D.inc, %D]
ret i32 %ret
}
define void @four_headers(i1 %PredEntry, i1 %PredX, i1 %PredY, i1 %PredD) {
; CHECK-LABEL: @four_headers(
; CHECK-NEXT: entry:
; CHECK-NEXT: br i1 [[PREDENTRY:%.*]], label [[X:%.*]], label [[Y:%.*]]
; CHECK: X:
; CHECK-NEXT: br label [[IRR_GUARD:%.*]]
; CHECK: Y:
; CHECK-NEXT: br label [[IRR_GUARD]]
; CHECK: A:
; CHECK-NEXT: br label [[IRR_GUARD]]
; CHECK: B:
; CHECK-NEXT: br label [[IRR_GUARD]]
; CHECK: C:
; CHECK-NEXT: br label [[IRR_GUARD]]
; CHECK: D:
; CHECK-NEXT: br i1 [[PREDD:%.*]], label [[EXIT:%.*]], label [[IRR_GUARD]]
; CHECK: exit:
; CHECK-NEXT: ret void
; CHECK: irr.guard:
; CHECK-NEXT: [[GUARD_A:%.*]] = phi i1 [ true, [[D:%.*]] ], [ [[PREDX:%.*]], [[X]] ], [ false, [[A:%.*]] ], [ false, [[B:%.*]] ], [ false, [[Y]] ], [ false, [[C:%.*]] ]
; CHECK-NEXT: [[GUARD_B:%.*]] = phi i1 [ false, [[D]] ], [ true, [[X]] ], [ true, [[A]] ], [ false, [[B]] ], [ false, [[Y]] ], [ false, [[C]] ]
; CHECK-NEXT: [[GUARD_C:%.*]] = phi i1 [ false, [[D]] ], [ false, [[X]] ], [ false, [[A]] ], [ true, [[B]] ], [ [[PREDY:%.*]], [[Y]] ], [ false, [[C]] ]
; CHECK-NEXT: br i1 [[GUARD_A]], label [[A]], label [[IRR_GUARD1:%.*]]
; CHECK: irr.guard1:
; CHECK-NEXT: br i1 [[GUARD_B]], label [[B]], label [[IRR_GUARD2:%.*]]
; CHECK: irr.guard2:
; CHECK-NEXT: br i1 [[GUARD_C]], label [[C]], label [[D]]
;
entry:
br i1 %PredEntry, label %X, label %Y
X:
br i1 %PredX, label %A, label %B
Y:
br i1 %PredY, label %C, label %D
A:
br label %B
B:
br label %C
C:
br label %D
D:
br i1 %PredD, label %exit, label %A
exit:
ret void
}
define i32 @hidden_nodes(i1 %PredEntry, i1 %PredA, i1 %PredB, i1 %PredC, i1 %PredD, i32 %X, i32 %Y) {
; CHECK-LABEL: @hidden_nodes(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[IRR_GUARD:%.*]]
; CHECK: A:
; CHECK-NEXT: [[A_INC:%.*]] = add i32 [[A_PHI_MOVED:%.*]], 1
; CHECK-NEXT: br label [[IRR_GUARD]]
; CHECK: B:
; CHECK-NEXT: br label [[C:%.*]]
; CHECK: C:
; CHECK-NEXT: [[C_INC:%.*]] = add i32 [[B_PHI_MOVED:%.*]], 1
; CHECK-NEXT: br label [[D:%.*]]
; CHECK: D:
; CHECK-NEXT: br i1 [[PREDD:%.*]], label [[EXIT:%.*]], label [[E:%.*]]
; CHECK: E:
; CHECK-NEXT: br label [[IRR_GUARD]]
; CHECK: exit:
; CHECK-NEXT: ret i32 [[B_PHI_MOVED]]
; CHECK: irr.guard:
; CHECK-NEXT: [[GUARD_A:%.*]] = phi i1 [ true, [[E]] ], [ [[PREDENTRY:%.*]], [[ENTRY:%.*]] ], [ false, [[A:%.*]] ]
; CHECK-NEXT: [[A_PHI_MOVED]] = phi i32 [ [[C_INC]], [[E]] ], [ [[X:%.*]], [[ENTRY]] ], [ [[A_PHI_MOVED]], [[A]] ]
; CHECK-NEXT: [[B_PHI_MOVED]] = phi i32 [ undef, [[E]] ], [ [[Y:%.*]], [[ENTRY]] ], [ [[A_INC]], [[A]] ]
; CHECK-NEXT: br i1 [[GUARD_A]], label [[A]], label [[B:%.*]]
;
entry:
br i1 %PredEntry, label %A, label %B
A:
%A.phi = phi i32 [%X, %entry], [%C.inc, %E]
%A.inc = add i32 %A.phi, 1
br label %B
B:
%B.phi = phi i32 [%A.inc, %A], [%Y, %entry]
br label %C
C:
%C.inc = add i32 %B.phi, 1
br label %D
D:
br i1 %PredD, label %exit, label %E
E:
br label %A
exit:
ret i32 %B.phi
}

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@ -0,0 +1,433 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -fix-irreducible -S | FileCheck %s -check-prefix=CHECK
define void @nested_irr_top_level(i1 %Pred0, i1 %Pred1, i1 %Pred2, i1 %Pred3, i1 %Pred4, i1 %Pred5) {
; CHECK-LABEL: @nested_irr_top_level(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[IRR_GUARD:%.*]]
; CHECK: A1:
; CHECK-NEXT: br label [[IRR_GUARD1:%.*]]
; CHECK: B1:
; CHECK-NEXT: br i1 [[PRED2:%.*]], label [[IRR_GUARD1]], label [[A3:%.*]]
; CHECK: B2:
; CHECK-NEXT: br i1 [[PRED3:%.*]], label [[IRR_GUARD1]], label [[A3]]
; CHECK: A3:
; CHECK-NEXT: br i1 [[PRED4:%.*]], label [[IRR_GUARD]], label [[EXIT:%.*]]
; CHECK: A2:
; CHECK-NEXT: br i1 [[PRED5:%.*]], label [[IRR_GUARD]], label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: ret void
; CHECK: irr.guard:
; CHECK-NEXT: [[GUARD_A1:%.*]] = phi i1 [ true, [[A2:%.*]] ], [ [[PRED0:%.*]], [[ENTRY:%.*]] ], [ false, [[A3]] ]
; CHECK-NEXT: br i1 [[GUARD_A1]], label [[A1:%.*]], label [[A2]]
; CHECK: irr.guard1:
; CHECK-NEXT: [[GUARD_B1:%.*]] = phi i1 [ true, [[B2:%.*]] ], [ [[PRED1:%.*]], [[A1]] ], [ false, [[B1:%.*]] ]
; CHECK-NEXT: br i1 [[GUARD_B1]], label [[B1]], label [[B2]]
;
entry:
br i1 %Pred0, label %A1, label %A2
A1:
br i1 %Pred1, label %B1, label %B2
B1:
br i1 %Pred2, label %B2, label %A3
B2:
br i1 %Pred3, label %B1, label %A3
A3:
br i1 %Pred4, label %A2, label %exit
A2:
br i1 %Pred5, label %A1, label %exit
exit:
ret void
}
define void @nested_irr_in_loop(i1 %Pred0, i1 %Pred1, i1 %Pred2, i1 %Pred3, i1 %Pred4, i1 %Pred5, i1 %Pred6) {
; CHECK-LABEL: @nested_irr_in_loop(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[H1:%.*]]
; CHECK: H1:
; CHECK-NEXT: br label [[IRR_GUARD:%.*]]
; CHECK: A1:
; CHECK-NEXT: br label [[IRR_GUARD1:%.*]]
; CHECK: B1:
; CHECK-NEXT: br i1 [[PRED2:%.*]], label [[IRR_GUARD1]], label [[A3:%.*]]
; CHECK: B2:
; CHECK-NEXT: br i1 [[PRED3:%.*]], label [[IRR_GUARD1]], label [[A3]]
; CHECK: A3:
; CHECK-NEXT: br i1 [[PRED4:%.*]], label [[IRR_GUARD]], label [[L1:%.*]]
; CHECK: A2:
; CHECK-NEXT: br i1 [[PRED5:%.*]], label [[IRR_GUARD]], label [[L1]]
; CHECK: L1:
; CHECK-NEXT: br i1 [[PRED6:%.*]], label [[EXIT:%.*]], label [[H1]]
; CHECK: exit:
; CHECK-NEXT: ret void
; CHECK: irr.guard:
; CHECK-NEXT: [[GUARD_A1:%.*]] = phi i1 [ true, [[A2:%.*]] ], [ [[PRED0:%.*]], [[H1]] ], [ false, [[A3]] ]
; CHECK-NEXT: br i1 [[GUARD_A1]], label [[A1:%.*]], label [[A2]]
; CHECK: irr.guard1:
; CHECK-NEXT: [[GUARD_B1:%.*]] = phi i1 [ true, [[B2:%.*]] ], [ [[PRED1:%.*]], [[A1]] ], [ false, [[B1:%.*]] ]
; CHECK-NEXT: br i1 [[GUARD_B1]], label [[B1]], label [[B2]]
;
entry:
br label %H1
H1:
br i1 %Pred0, label %A1, label %A2
A1:
br i1 %Pred1, label %B1, label %B2
B1:
br i1 %Pred2, label %B2, label %A3
B2:
br i1 %Pred3, label %B1, label %A3
A3:
br i1 %Pred4, label %A2, label %L1
A2:
br i1 %Pred5, label %A1, label %L1
L1:
br i1 %Pred6, label %exit, label %H1
exit:
ret void
}
define void @loop_in_irr(i1 %Pred0, i1 %Pred1, i1 %Pred2) {
; CHECK-LABEL: @loop_in_irr(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[IRR_GUARD:%.*]]
; CHECK: A1:
; CHECK-NEXT: br label [[H1:%.*]]
; CHECK: H1:
; CHECK-NEXT: br label [[L1:%.*]]
; CHECK: L1:
; CHECK-NEXT: br i1 [[PRED1:%.*]], label [[H1]], label [[A3:%.*]]
; CHECK: A3:
; CHECK-NEXT: br i1 [[PRED2:%.*]], label [[IRR_GUARD]], label [[EXIT:%.*]]
; CHECK: A2:
; CHECK-NEXT: br label [[IRR_GUARD]]
; CHECK: exit:
; CHECK-NEXT: ret void
; CHECK: irr.guard:
; CHECK-NEXT: [[GUARD_A1:%.*]] = phi i1 [ true, [[A2:%.*]] ], [ [[PRED0:%.*]], [[ENTRY:%.*]] ], [ false, [[A3]] ]
; CHECK-NEXT: br i1 [[GUARD_A1]], label [[A1:%.*]], label [[A2]]
;
entry:
br i1 %Pred0, label %A1, label %A2
A1:
br label %H1
H1:
br label %L1
L1:
br i1 %Pred1, label %H1, label %A3
A3:
br i1 %Pred2, label %A2, label %exit
A2:
br label %A1
exit:
ret void
}
define void @loop_in_irr_shared_header(i1 %Pred0, i1 %Pred1, i1 %Pred2) {
; CHECK-LABEL: @loop_in_irr_shared_header(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[IRR_GUARD:%.*]]
; CHECK: H1:
; CHECK-NEXT: br label [[L1:%.*]]
; CHECK: L1:
; CHECK-NEXT: br i1 [[PRED1:%.*]], label [[IRR_GUARD]], label [[A3:%.*]]
; CHECK: A3:
; CHECK-NEXT: br i1 [[PRED2:%.*]], label [[IRR_GUARD]], label [[EXIT:%.*]]
; CHECK: A2:
; CHECK-NEXT: br label [[IRR_GUARD]]
; CHECK: exit:
; CHECK-NEXT: ret void
; CHECK: irr.guard:
; CHECK-NEXT: [[GUARD_H1:%.*]] = phi i1 [ true, [[A2:%.*]] ], [ true, [[L1]] ], [ [[PRED0:%.*]], [[ENTRY:%.*]] ], [ false, [[A3]] ]
; CHECK-NEXT: br i1 [[GUARD_H1]], label [[H1:%.*]], label [[A2]]
;
entry:
br i1 %Pred0, label %H1, label %A2
H1:
br label %L1
L1:
br i1 %Pred1, label %H1, label %A3
A3:
br i1 %Pred2, label %A2, label %exit
A2:
br label %H1
exit:
ret void
}
define void @siblings_top_level(i1 %Pred0, i1 %Pred1, i1 %Pred2, i1 %Pred3, i1 %Pred4, i1 %Pred5, i1 %Pred6) {
; CHECK-LABEL: @siblings_top_level(
; CHECK-NEXT: entry:
; CHECK-NEXT: br i1 [[PRED0:%.*]], label [[H1:%.*]], label [[FORK1:%.*]]
; CHECK: H1:
; CHECK-NEXT: br label [[IRR_GUARD1:%.*]]
; CHECK: A1:
; CHECK-NEXT: br label [[IRR_GUARD1]]
; CHECK: A2:
; CHECK-NEXT: br i1 [[PRED2:%.*]], label [[IRR_GUARD1]], label [[L1:%.*]]
; CHECK: L1:
; CHECK-NEXT: br i1 [[PRED3:%.*]], label [[H1]], label [[EXIT:%.*]]
; CHECK: fork1:
; CHECK-NEXT: br label [[IRR_GUARD:%.*]]
; CHECK: B1:
; CHECK-NEXT: br label [[H2:%.*]]
; CHECK: H2:
; CHECK-NEXT: br label [[L2:%.*]]
; CHECK: L2:
; CHECK-NEXT: br i1 [[PRED5:%.*]], label [[H2]], label [[IRR_GUARD]]
; CHECK: B2:
; CHECK-NEXT: br i1 [[PRED6:%.*]], label [[IRR_GUARD]], label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: ret void
; CHECK: irr.guard:
; CHECK-NEXT: [[GUARD_B1:%.*]] = phi i1 [ true, [[B2:%.*]] ], [ [[PRED4:%.*]], [[FORK1]] ], [ false, [[L2]] ]
; CHECK-NEXT: br i1 [[GUARD_B1]], label [[B1:%.*]], label [[B2]]
; CHECK: irr.guard1:
; CHECK-NEXT: [[GUARD_A1:%.*]] = phi i1 [ true, [[A2:%.*]] ], [ [[PRED1:%.*]], [[H1]] ], [ false, [[A1:%.*]] ]
; CHECK-NEXT: br i1 [[GUARD_A1]], label [[A1]], label [[A2]]
;
entry:
br i1 %Pred0, label %H1, label %fork1
H1:
br i1 %Pred1, label %A1, label %A2
A1:
br label %A2
A2:
br i1 %Pred2, label %A1, label %L1
L1:
br i1 %Pred3, label %H1, label %exit
fork1:
br i1 %Pred4, label %B1, label %B2
B1:
br label %H2
H2:
br label %L2
L2:
br i1 %Pred5, label %H2, label %B2
B2:
br i1 %Pred6, label %B1, label %exit
exit:
ret void
}
define void @siblings_in_loop(i1 %Pred0, i1 %Pred1, i1 %Pred2, i1 %Pred3, i1 %Pred4, i1 %Pred5, i1 %Pred6, i1 %Pred7) {
; CHECK-LABEL: @siblings_in_loop(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[H0:%.*]]
; CHECK: H0:
; CHECK-NEXT: br i1 [[PRED0:%.*]], label [[H1:%.*]], label [[FORK1:%.*]]
; CHECK: H1:
; CHECK-NEXT: br label [[IRR_GUARD1:%.*]]
; CHECK: A1:
; CHECK-NEXT: br label [[IRR_GUARD1]]
; CHECK: A2:
; CHECK-NEXT: br i1 [[PRED2:%.*]], label [[IRR_GUARD1]], label [[L1:%.*]]
; CHECK: L1:
; CHECK-NEXT: br i1 [[PRED3:%.*]], label [[H1]], label [[L0:%.*]]
; CHECK: fork1:
; CHECK-NEXT: br label [[IRR_GUARD:%.*]]
; CHECK: B1:
; CHECK-NEXT: br label [[H2:%.*]]
; CHECK: H2:
; CHECK-NEXT: br label [[L2:%.*]]
; CHECK: L2:
; CHECK-NEXT: br i1 [[PRED5:%.*]], label [[H2]], label [[IRR_GUARD]]
; CHECK: B2:
; CHECK-NEXT: br i1 [[PRED6:%.*]], label [[IRR_GUARD]], label [[L0]]
; CHECK: L0:
; CHECK-NEXT: br i1 [[PRED7:%.*]], label [[EXIT:%.*]], label [[H0]]
; CHECK: exit:
; CHECK-NEXT: ret void
; CHECK: irr.guard:
; CHECK-NEXT: [[GUARD_B1:%.*]] = phi i1 [ true, [[B2:%.*]] ], [ [[PRED4:%.*]], [[FORK1]] ], [ false, [[L2]] ]
; CHECK-NEXT: br i1 [[GUARD_B1]], label [[B1:%.*]], label [[B2]]
; CHECK: irr.guard1:
; CHECK-NEXT: [[GUARD_A1:%.*]] = phi i1 [ true, [[A2:%.*]] ], [ [[PRED1:%.*]], [[H1]] ], [ false, [[A1:%.*]] ]
; CHECK-NEXT: br i1 [[GUARD_A1]], label [[A1]], label [[A2]]
;
entry:
br label %H0
H0:
br i1 %Pred0, label %H1, label %fork1
H1:
br i1 %Pred1, label %A1, label %A2
A1:
br label %A2
A2:
br i1 %Pred2, label %A1, label %L1
L1:
br i1 %Pred3, label %H1, label %L0
fork1:
br i1 %Pred4, label %B1, label %B2
B1:
br label %H2
H2:
br label %L2
L2:
br i1 %Pred5, label %H2, label %B2
B2:
br i1 %Pred6, label %B1, label %L0
L0:
br i1 %Pred7, label %exit, label %H0
exit:
ret void
}
define void @irreducible_mountain_bug(i1 %Pred0, i1 %Pred1, i1 %Pred2, i1 %Pred3, i1 %Pred4, i1 %Pred5, i1 %Pred6, i1 %Pred7, i1 %Pred8, i1 %Pred9, i1 %Pred10, i1 %Pred11, i1 %Pred12, i1 %Pred13) {
; CHECK-LABEL: @irreducible_mountain_bug(
; CHECK-NEXT: entry:
; CHECK-NEXT: br i1 [[PRED0:%.*]], label [[IF_END:%.*]], label [[IF_THEN:%.*]]
; CHECK: if.end:
; CHECK-NEXT: br i1 [[PRED1:%.*]], label [[IF_THEN7:%.*]], label [[IF_ELSE:%.*]]
; CHECK: if.then7:
; CHECK-NEXT: br label [[IF_END16:%.*]]
; CHECK: if.else:
; CHECK-NEXT: br label [[IF_END16]]
; CHECK: if.end16:
; CHECK-NEXT: br i1 [[PRED2:%.*]], label [[WHILE_COND_PREHEADER:%.*]], label [[IF_THEN39:%.*]]
; CHECK: while.cond.preheader:
; CHECK-NEXT: br label [[WHILE_COND:%.*]]
; CHECK: while.cond:
; CHECK-NEXT: br i1 [[PRED3:%.*]], label [[IRR_GUARD:%.*]], label [[LOR_RHS:%.*]]
; CHECK: cond.true49:
; CHECK-NEXT: br i1 [[PRED4:%.*]], label [[IF_THEN69:%.*]], label [[WHILE_BODY63:%.*]]
; CHECK: while.body63:
; CHECK-NEXT: br i1 [[PRED5:%.*]], label [[EXIT:%.*]], label [[WHILE_COND47:%.*]]
; CHECK: while.cond47:
; CHECK-NEXT: br label [[IRR_GUARD]]
; CHECK: cond.end61:
; CHECK-NEXT: br i1 [[PRED7:%.*]], label [[WHILE_BODY63]], label [[WHILE_COND]]
; CHECK: if.then69:
; CHECK-NEXT: br i1 [[PRED8:%.*]], label [[EXIT]], label [[WHILE_COND]]
; CHECK: lor.rhs:
; CHECK-NEXT: br i1 [[PRED9:%.*]], label [[IRR_GUARD]], label [[WHILE_END76:%.*]]
; CHECK: while.end76:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: if.then39:
; CHECK-NEXT: br i1 [[PRED10:%.*]], label [[EXIT]], label [[IF_END_I145:%.*]]
; CHECK: if.end.i145:
; CHECK-NEXT: br i1 [[PRED11:%.*]], label [[EXIT]], label [[IF_END8_I149:%.*]]
; CHECK: if.end8.i149:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: if.then:
; CHECK-NEXT: br i1 [[PRED12:%.*]], label [[EXIT]], label [[IF_END_I:%.*]]
; CHECK: if.end.i:
; CHECK-NEXT: br i1 [[PRED13:%.*]], label [[EXIT]], label [[IF_END8_I:%.*]]
; CHECK: if.end8.i:
; CHECK-NEXT: br label [[EXIT]]
; CHECK: exit:
; CHECK-NEXT: ret void
; CHECK: irr.guard:
; CHECK-NEXT: [[GUARD_COND_TRUE49:%.*]] = phi i1 [ [[PRED6:%.*]], [[WHILE_COND47]] ], [ true, [[WHILE_COND]] ], [ false, [[LOR_RHS]] ]
; CHECK-NEXT: br i1 [[GUARD_COND_TRUE49]], label [[COND_TRUE49:%.*]], label [[COND_END61:%.*]]
;
entry:
br i1 %Pred0, label %if.end, label %if.then
if.end:
br i1 %Pred1, label %if.then7, label %if.else
if.then7:
br label %if.end16
if.else:
br label %if.end16
if.end16:
br i1 %Pred2, label %while.cond.preheader, label %if.then39
while.cond.preheader:
br label %while.cond
while.cond:
br i1 %Pred3, label %cond.true49, label %lor.rhs
cond.true49:
br i1 %Pred4, label %if.then69, label %while.body63
while.body63:
br i1 %Pred5, label %exit, label %while.cond47
while.cond47:
br i1 %Pred6, label %cond.true49, label %cond.end61
cond.end61:
br i1 %Pred7, label %while.body63, label %while.cond
if.then69:
br i1 %Pred8, label %exit, label %while.cond
lor.rhs:
br i1 %Pred9, label %cond.end61, label %while.end76
while.end76:
br label %exit
if.then39:
br i1 %Pred10, label %exit, label %if.end.i145
if.end.i145:
br i1 %Pred11, label %exit, label %if.end8.i149
if.end8.i149:
br label %exit
if.then:
br i1 %Pred12, label %exit, label %if.end.i
if.end.i:
br i1 %Pred13, label %exit, label %if.end8.i
if.end8.i:
br label %exit
exit:
ret void
}

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@ -0,0 +1,43 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -fix-irreducible -S | FileCheck %s
define void @loop_1(i32 %Value, i1 %PredEntry, i1 %PredD) {
; CHECK-LABEL: @loop_1(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[IRR_GUARD:%.*]]
; CHECK: A:
; CHECK-NEXT: br label [[IRR_GUARD]]
; CHECK: B:
; CHECK-NEXT: br label [[NODEBLOCK:%.*]]
; CHECK: NodeBlock:
; CHECK-NEXT: [[PIVOT:%.*]] = icmp slt i32 [[VALUE:%.*]], 1
; CHECK-NEXT: br i1 [[PIVOT]], label [[LEAFBLOCK:%.*]], label [[LEAFBLOCK1:%.*]]
; CHECK: LeafBlock1:
; CHECK-NEXT: [[SWITCHLEAF2:%.*]] = icmp eq i32 [[VALUE]], 1
; CHECK-NEXT: br i1 [[SWITCHLEAF2]], label [[IRR_GUARD]], label [[NEWDEFAULT:%.*]]
; CHECK: LeafBlock:
; CHECK-NEXT: [[SWITCHLEAF:%.*]] = icmp eq i32 [[VALUE]], 0
; CHECK-NEXT: br i1 [[SWITCHLEAF]], label [[IRR_GUARD]], label [[NEWDEFAULT]]
; CHECK: NewDefault:
; CHECK-NEXT: br label [[EXIT:%.*]]
; CHECK: exit:
; CHECK-NEXT: ret void
; CHECK: irr.guard:
; CHECK-NEXT: [[GUARD_A:%.*]] = phi i1 [ true, [[LEAFBLOCK]] ], [ [[PREDENTRY:%.*]], [[ENTRY:%.*]] ], [ false, [[LEAFBLOCK1]] ], [ false, [[A:%.*]] ]
; CHECK-NEXT: br i1 [[GUARD_A]], label [[A]], label [[B:%.*]]
;
entry:
br i1 %PredEntry, label %A, label %B
A:
br label %B
B:
switch i32 %Value, label %exit [
i32 0, label %A
i32 1, label %B
]
exit:
ret void
}

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@ -0,0 +1,60 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -fix-irreducible -structurizecfg -S | FileCheck %s
; Both B1 and B4 are headers of an irreducible cycle. But in the
; structurized version, B1 dominates B4. The program is structurized
; correctly when the irreducible cycle is fixed.
define void @irreducible(i1 %PredEntry, i1 %PredB1, i1 %PredB2, i1 %PredB3, i1 %PredB4)
; CHECK-LABEL: @irreducible(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[PREDB2_INV:%.*]] = xor i1 [[PREDB2:%.*]], true
; CHECK-NEXT: [[PREDB1_INV:%.*]] = xor i1 [[PREDB1:%.*]], true
; CHECK-NEXT: br label [[IRR_GUARD:%.*]]
; CHECK: Flow:
; CHECK-NEXT: [[TMP0:%.*]] = phi i1 [ [[PREDB4:%.*]], [[B4:%.*]] ], [ false, [[IRR_GUARD]] ]
; CHECK-NEXT: [[TMP1:%.*]] = phi i1 [ false, [[B4]] ], [ true, [[IRR_GUARD]] ]
; CHECK-NEXT: br i1 [[TMP1]], label [[B1:%.*]], label [[FLOW1:%.*]]
; CHECK: B1:
; CHECK-NEXT: br label [[FLOW1]]
; CHECK: Flow1:
; CHECK-NEXT: [[TMP2:%.*]] = phi i1 [ [[PREDB1_INV]], [[B1]] ], [ [[TMP0]], [[FLOW:%.*]] ]
; CHECK-NEXT: br i1 [[TMP2]], label [[B2:%.*]], label [[FLOW2:%.*]]
; CHECK: B2:
; CHECK-NEXT: br i1 [[PREDB2_INV]], label [[B3:%.*]], label [[FLOW3:%.*]]
; CHECK: Flow2:
; CHECK-NEXT: [[TMP3:%.*]] = phi i1 [ [[TMP4:%.*]], [[FLOW3]] ], [ true, [[FLOW1]] ]
; CHECK-NEXT: br i1 [[TMP3]], label [[EXIT:%.*]], label [[IRR_GUARD]]
; CHECK: B3:
; CHECK-NEXT: br label [[FLOW3]]
; CHECK: B4:
; CHECK-NEXT: br label [[FLOW]]
; CHECK: Flow3:
; CHECK-NEXT: [[TMP4]] = phi i1 [ false, [[B3]] ], [ true, [[B2]] ]
; CHECK-NEXT: br label [[FLOW2]]
; CHECK: exit:
; CHECK-NEXT: ret void
; CHECK: irr.guard:
; CHECK-NEXT: [[GUARD_B1:%.*]] = phi i1 [ [[PREDENTRY:%.*]], [[ENTRY:%.*]] ], [ [[PREDB3:%.*]], [[FLOW2]] ]
; CHECK-NEXT: [[TMP5:%.*]] = xor i1 [[GUARD_B1]], true
; CHECK-NEXT: br i1 [[TMP5]], label [[B4]], label [[FLOW]]
;
{
entry:
br i1 %PredEntry, label %B1, label %B4
B1:
br i1 %PredB1, label %exit, label %B2
B2:
br i1 %PredB2, label %exit, label %B3
B3:
br i1 %PredB3, label %B1, label %B4
B4:
br i1 %PredB4, label %B2, label %exit
exit:
ret void
}

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@ -0,0 +1,186 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -fix-irreducible -unify-loop-exits -structurizecfg -S | FileCheck %s
define void @irreducible_mountain_bug(i1 %Pred0, i1 %Pred1, i1 %Pred2, i1 %Pred3, i1 %Pred4, i1 %Pred5, i1 %Pred6, i1 %Pred7, i1 %Pred8, i1 %Pred9, i1 %Pred10, i1 %Pred11, i1 %Pred12, i1 %Pred13) {
; CHECK-LABEL: @irreducible_mountain_bug(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[PRED0_INV:%.*]] = xor i1 [[PRED0:%.*]], true
; CHECK-NEXT: [[PRED1_INV:%.*]] = xor i1 [[PRED1:%.*]], true
; CHECK-NEXT: [[PRED2_INV:%.*]] = xor i1 [[PRED2:%.*]], true
; CHECK-NEXT: [[PRED3_INV:%.*]] = xor i1 [[PRED3:%.*]], true
; CHECK-NEXT: [[PRED5_INV:%.*]] = xor i1 [[PRED5:%.*]], true
; CHECK-NEXT: [[PRED4_INV:%.*]] = xor i1 [[PRED4:%.*]], true
; CHECK-NEXT: [[PRED10_INV:%.*]] = xor i1 [[PRED10:%.*]], true
; CHECK-NEXT: [[PRED11_INV:%.*]] = xor i1 [[PRED11:%.*]], true
; CHECK-NEXT: [[PRED12_INV:%.*]] = xor i1 [[PRED12:%.*]], true
; CHECK-NEXT: [[PRED13_INV:%.*]] = xor i1 [[PRED13:%.*]], true
; CHECK-NEXT: br i1 [[PRED0_INV]], label [[IF_THEN:%.*]], label [[FLOW18:%.*]]
; CHECK: Flow18:
; CHECK-NEXT: [[TMP0:%.*]] = phi i1 [ false, [[FLOW3:%.*]] ], [ true, [[ENTRY:%.*]] ]
; CHECK-NEXT: br i1 [[TMP0]], label [[IF_END:%.*]], label [[FLOW19:%.*]]
; CHECK: if.end:
; CHECK-NEXT: br i1 [[PRED1_INV]], label [[IF_ELSE:%.*]], label [[FLOW17:%.*]]
; CHECK: Flow17:
; CHECK-NEXT: [[TMP1:%.*]] = phi i1 [ false, [[IF_ELSE]] ], [ true, [[IF_END]] ]
; CHECK-NEXT: br i1 [[TMP1]], label [[IF_THEN7:%.*]], label [[IF_END16:%.*]]
; CHECK: if.then7:
; CHECK-NEXT: br label [[IF_END16]]
; CHECK: if.else:
; CHECK-NEXT: br label [[FLOW17]]
; CHECK: Flow19:
; CHECK-NEXT: br label [[EXIT:%.*]]
; CHECK: if.end16:
; CHECK-NEXT: br i1 [[PRED2_INV]], label [[IF_THEN39:%.*]], label [[FLOW15:%.*]]
; CHECK: Flow15:
; CHECK-NEXT: [[TMP2:%.*]] = phi i1 [ false, [[FLOW5:%.*]] ], [ true, [[IF_END16]] ]
; CHECK-NEXT: br i1 [[TMP2]], label [[WHILE_COND_PREHEADER:%.*]], label [[FLOW16:%.*]]
; CHECK: while.cond.preheader:
; CHECK-NEXT: br label [[WHILE_COND:%.*]]
; CHECK: Flow16:
; CHECK-NEXT: br label [[FLOW19]]
; CHECK: while.cond:
; CHECK-NEXT: br i1 [[PRED3_INV]], label [[LOR_RHS:%.*]], label [[FLOW11:%.*]]
; CHECK: Flow7:
; CHECK-NEXT: [[TMP3:%.*]] = phi i1 [ [[PRED7:%.*]], [[COND_END61:%.*]] ], [ false, [[IRR_GUARD:%.*]] ]
; CHECK-NEXT: [[TMP4:%.*]] = phi i1 [ false, [[COND_END61]] ], [ true, [[IRR_GUARD]] ]
; CHECK-NEXT: br i1 [[TMP4]], label [[COND_TRUE49:%.*]], label [[FLOW8:%.*]]
; CHECK: cond.true49:
; CHECK-NEXT: br label [[FLOW8]]
; CHECK: Flow8:
; CHECK-NEXT: [[TMP5:%.*]] = phi i1 [ false, [[COND_TRUE49]] ], [ true, [[FLOW7:%.*]] ]
; CHECK-NEXT: [[TMP6:%.*]] = phi i1 [ [[PRED4_INV]], [[COND_TRUE49]] ], [ [[TMP3]], [[FLOW7]] ]
; CHECK-NEXT: br i1 [[TMP6]], label [[WHILE_BODY63:%.*]], label [[FLOW9:%.*]]
; CHECK: while.body63:
; CHECK-NEXT: br i1 [[PRED5_INV]], label [[WHILE_COND47:%.*]], label [[FLOW10:%.*]]
; CHECK: Flow9:
; CHECK-NEXT: [[TMP7:%.*]] = phi i1 [ true, [[FLOW10]] ], [ false, [[FLOW8]] ]
; CHECK-NEXT: [[TMP8:%.*]] = phi i1 [ false, [[FLOW10]] ], [ [[TMP5]], [[FLOW8]] ]
; CHECK-NEXT: [[TMP9:%.*]] = phi i1 [ [[TMP18:%.*]], [[FLOW10]] ], [ true, [[FLOW8]] ]
; CHECK-NEXT: [[TMP10:%.*]] = xor i1 [[TMP7]], true
; CHECK-NEXT: [[TMP11:%.*]] = xor i1 [[TMP8]], true
; CHECK-NEXT: br i1 [[TMP9]], label [[LOOP_EXIT_GUARD1:%.*]], label [[IRR_GUARD]]
; CHECK: while.cond47:
; CHECK-NEXT: br label [[FLOW10]]
; CHECK: cond.end61:
; CHECK-NEXT: br label [[FLOW7]]
; CHECK: Flow13:
; CHECK-NEXT: [[TMP12:%.*]] = phi i1 [ false, [[FLOW14:%.*]] ], [ true, [[LOOP_EXIT_GUARD1]] ]
; CHECK-NEXT: [[TMP13:%.*]] = phi i1 [ [[TMP17:%.*]], [[FLOW14]] ], [ [[TMP11]], [[LOOP_EXIT_GUARD1]] ]
; CHECK-NEXT: br label [[FLOW12:%.*]]
; CHECK: if.then69:
; CHECK-NEXT: br label [[FLOW14]]
; CHECK: lor.rhs:
; CHECK-NEXT: br label [[FLOW11]]
; CHECK: while.end76:
; CHECK-NEXT: br label [[FLOW6:%.*]]
; CHECK: if.then39:
; CHECK-NEXT: br i1 [[PRED10_INV]], label [[IF_END_I145:%.*]], label [[FLOW5]]
; CHECK: if.end.i145:
; CHECK-NEXT: br i1 [[PRED11_INV]], label [[IF_END8_I149:%.*]], label [[FLOW4:%.*]]
; CHECK: if.end8.i149:
; CHECK-NEXT: br label [[FLOW4]]
; CHECK: if.then:
; CHECK-NEXT: br i1 [[PRED12_INV]], label [[IF_END_I:%.*]], label [[FLOW3]]
; CHECK: if.end.i:
; CHECK-NEXT: br i1 [[PRED13_INV]], label [[IF_END8_I:%.*]], label [[FLOW:%.*]]
; CHECK: if.end8.i:
; CHECK-NEXT: br label [[FLOW]]
; CHECK: Flow:
; CHECK-NEXT: br label [[FLOW3]]
; CHECK: Flow3:
; CHECK-NEXT: br label [[FLOW18]]
; CHECK: Flow4:
; CHECK-NEXT: br label [[FLOW5]]
; CHECK: Flow5:
; CHECK-NEXT: br label [[FLOW15]]
; CHECK: Flow6:
; CHECK-NEXT: br label [[FLOW16]]
; CHECK: exit:
; CHECK-NEXT: ret void
; CHECK: Flow11:
; CHECK-NEXT: [[TMP14:%.*]] = phi i1 [ false, [[LOR_RHS]] ], [ true, [[WHILE_COND]] ]
; CHECK-NEXT: [[TMP15:%.*]] = phi i1 [ [[PRED9:%.*]], [[LOR_RHS]] ], [ [[PRED3]], [[WHILE_COND]] ]
; CHECK-NEXT: br i1 [[TMP15]], label [[IRR_GUARD]], label [[FLOW12]]
; CHECK: irr.guard:
; CHECK-NEXT: [[GUARD_COND_TRUE49:%.*]] = phi i1 [ [[PRED6:%.*]], [[FLOW9]] ], [ [[TMP14]], [[FLOW11]] ]
; CHECK-NEXT: [[TMP16:%.*]] = xor i1 [[GUARD_COND_TRUE49]], true
; CHECK-NEXT: br i1 [[TMP16]], label [[COND_END61]], label [[FLOW7]]
; CHECK: Flow14:
; CHECK-NEXT: [[TMP17]] = phi i1 [ [[PRED8:%.*]], [[IF_THEN69:%.*]] ], [ [[TMP11]], [[LOOP_EXIT_GUARD2:%.*]] ]
; CHECK-NEXT: br label [[FLOW13:%.*]]
; CHECK: loop.exit.guard:
; CHECK-NEXT: br i1 [[TMP19:%.*]], label [[WHILE_END76:%.*]], label [[FLOW6]]
; CHECK: Flow10:
; CHECK-NEXT: [[TMP18]] = phi i1 [ false, [[WHILE_COND47]] ], [ true, [[WHILE_BODY63]] ]
; CHECK-NEXT: br label [[FLOW9]]
; CHECK: Flow12:
; CHECK-NEXT: [[TMP19]] = phi i1 [ [[TMP12]], [[FLOW13]] ], [ true, [[FLOW11]] ]
; CHECK-NEXT: [[TMP20:%.*]] = phi i1 [ [[TMP13]], [[FLOW13]] ], [ true, [[FLOW11]] ]
; CHECK-NEXT: br i1 [[TMP20]], label [[LOOP_EXIT_GUARD:%.*]], label [[WHILE_COND]]
; CHECK: loop.exit.guard1:
; CHECK-NEXT: br i1 [[TMP11]], label [[LOOP_EXIT_GUARD2]], label [[FLOW13]]
; CHECK: loop.exit.guard2:
; CHECK-NEXT: br i1 [[TMP10]], label [[IF_THEN69]], label [[FLOW14]]
;
entry:
br i1 %Pred0, label %if.end, label %if.then
if.end:
br i1 %Pred1, label %if.then7, label %if.else
if.then7:
br label %if.end16
if.else:
br label %if.end16
if.end16:
br i1 %Pred2, label %while.cond.preheader, label %if.then39
while.cond.preheader:
br label %while.cond
while.cond:
br i1 %Pred3, label %cond.true49, label %lor.rhs
cond.true49:
br i1 %Pred4, label %if.then69, label %while.body63
while.body63:
br i1 %Pred5, label %exit, label %while.cond47
while.cond47:
br i1 %Pred6, label %cond.true49, label %cond.end61
cond.end61:
br i1 %Pred7, label %while.body63, label %while.cond
if.then69:
br i1 %Pred8, label %exit, label %while.cond
lor.rhs:
br i1 %Pred9, label %cond.end61, label %while.end76
while.end76:
br label %exit
if.then39:
br i1 %Pred10, label %exit, label %if.end.i145
if.end.i145:
br i1 %Pred11, label %exit, label %if.end8.i149
if.end8.i149:
br label %exit
if.then:
br i1 %Pred12, label %exit, label %if.end.i
if.end.i:
br i1 %Pred13, label %exit, label %if.end8.i
if.end8.i:
br label %exit
exit:
ret void
}