[llvm-commits] [llvm] r146578 - in /llvm/trunk: lib/Transforms/Scalar/LoopUnswitch.cpp test/Transforms/LoopUnswitch/2011-11-18-SimpleSwitch.ll test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches-Threshold.ll test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches.ll
Stepan Dyatkovskiy
stpworld at narod.ru
Thu Dec 22 01:59:56 PST 2011
OK. Thanks, Chad. Now I have a time and I look at it.
-Stepan.
Chad Rosier wrote:
> Hi Stepan,
> I noticed this patch caused an ~8% compile-time regression for MultiSource/Benchmarks/Prolangs-C++/shapes/shapes for ARMv7 -O3 -mthumb. If you have a moment would you mind taking a look? The test-suite can be downloaded from the llvm repository (See: http://llvm.org/docs/TestingGuide.html#testsuite). Here are the command line arguments I used to reproduce the regression:
>
> /Users/mcrosier/llvm-clean/Release+Asserts/Release+Asserts/bin/clang++ -I/Users/mcrosier/llvm-clean/Release+Asserts/projects/test-suite/MultiSource/Benchmarks/Prolangs-C++/shapes -I/Users/mcrosier/llvm-clean/llvm/projects/test-suite/MultiSource/Benchmarks/Prolangs-C++/shapes -I/Users/mcrosier/llvm-clean/Release+Asserts/projects/test-suite/../../../llvm/projects/test-suite/include -I../../../../include -I/Users/mcrosier/llvm-clean/Release+Asserts/include -I/Users/mcrosier/llvm-clean/llvm/include -D_GNU_SOURCE -D__STDC_LIMIT_MACROS -DNDEBUG -DSMALL_PROBLEM_SIZE -O3 -mthumb -miphoneos-version-min=4.0 -Wl,--no-demangle -ccc-install-dir /Developer/Platforms/iPhoneOS.platform/Developer/usr/bin -arch armv7 -isysroot /Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS6.0.Internal.sdk -c /Users/mcrosier/llvm-clean/llvm/projects/test-suite/MultiSource/Benchmarks/Prolangs-C++/shapes/bjarne.cpp -o Output/bjarne.llvm.o
>
> Chad
>
> For Apple's record this is being tracked by<rdar://problem/10601498>.
>
> On Dec 14, 2011, at 11:19 AM, Stepan Dyatkovskiy wrote:
>
>> Author: dyatkovskiy
>> Date: Wed Dec 14 13:19:17 2011
>> New Revision: 146578
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=146578&view=rev
>> Log:
>> Fix for bug #11429: Wrong behaviour for switches. Small improvement for code size heuristics.
>>
>> Added:
>> llvm/trunk/test/Transforms/LoopUnswitch/2011-11-18-SimpleSwitch.ll
>> llvm/trunk/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches-Threshold.ll
>> llvm/trunk/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches.ll
>> Modified:
>> llvm/trunk/lib/Transforms/Scalar/LoopUnswitch.cpp
>>
>> Modified: llvm/trunk/lib/Transforms/Scalar/LoopUnswitch.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopUnswitch.cpp?rev=146578&r1=146577&r2=146578&view=diff
>> ==============================================================================
>> --- llvm/trunk/lib/Transforms/Scalar/LoopUnswitch.cpp (original)
>> +++ llvm/trunk/lib/Transforms/Scalar/LoopUnswitch.cpp Wed Dec 14 13:19:17 2011
>> @@ -71,7 +71,9 @@
>> // LoopProcessWorklist - Used to check if second loop needs processing
>> // after RewriteLoopBodyWithConditionConstant rewrites first loop.
>> std::vector<Loop*> LoopProcessWorklist;
>> - SmallPtrSet<Value *,8> UnswitchedVals;
>> +
>> + // FIXME: Consider custom class for this.
>> + std::map<const SwitchInst*, SmallPtrSet<const Value *,8> > UnswitchedVals;
>>
>> bool OptimizeForSize;
>> bool redoLoop;
>> @@ -117,7 +119,15 @@
>> private:
>>
>> virtual void releaseMemory() {
>> - UnswitchedVals.clear();
>> + // We need to forget about all switches in the current loop.
>> + // FIXME: Do it better than enumerating all blocks of code
>> + // and see if it is a switch instruction.
>> + for (Loop::block_iterator I = currentLoop->block_begin(),
>> + E = currentLoop->block_end(); I != E; ++I) {
>> + SwitchInst* SI = dyn_cast<SwitchInst>((*I)->getTerminator());
>> + if (SI)
>> + UnswitchedVals.erase(SI);
>> + }
>> }
>>
>> /// RemoveLoopFromWorklist - If the specified loop is on the loop worklist,
>> @@ -128,6 +138,12 @@
>> if (I != LoopProcessWorklist.end())
>> LoopProcessWorklist.erase(I);
>> }
>> +
>> + /// For new loop switches we clone info about values that was
>> + /// already unswitched and has redundant successors.
>> + /// Note, that new loop data is stored inside the VMap.
>> + void CloneUnswitchedVals(const ValueToValueMapTy& VMap,
>> + const BasicBlock* SrcBB);
>>
>> void initLoopData() {
>> loopHeader = currentLoop->getHeader();
>> @@ -255,13 +271,25 @@
>> } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
>> Value *LoopCond = FindLIVLoopCondition(SI->getCondition(),
>> currentLoop, Changed);
>> - if (LoopCond&& SI->getNumCases()> 1) {
>> + unsigned NumCases = SI->getNumCases();
>> + if (LoopCond&& NumCases> 1) {
>> // Find a value to unswitch on:
>> // FIXME: this should chose the most expensive case!
>> // FIXME: scan for a case with a non-critical edge?
>> - Constant *UnswitchVal = SI->getCaseValue(1);
>> + Constant *UnswitchVal = NULL;
>> +
>> // Do not process same value again and again.
>> - if (!UnswitchedVals.insert(UnswitchVal))
>> + // At this point we have some cases already unswitched and
>> + // some not yet unswitched. Let's find the first not yet unswitched one.
>> + for (unsigned i = 1; i< NumCases; ++i) {
>> + Constant* UnswitchValCandidate = SI->getCaseValue(i);
>> + if (!UnswitchedVals[SI].count(UnswitchValCandidate)) {
>> + UnswitchVal = UnswitchValCandidate;
>> + break;
>> + }
>> + }
>> +
>> + if (!UnswitchVal)
>> continue;
>>
>> if (UnswitchIfProfitable(LoopCond, UnswitchVal)) {
>> @@ -287,6 +315,23 @@
>> return Changed;
>> }
>>
>> +/// For new loop switches we clone info about values that was
>> +/// already unswitched and has redundant successors.
>> +/// Not that new loop data is stored inside the VMap.
>> +void LoopUnswitch::CloneUnswitchedVals(const ValueToValueMapTy& VMap,
>> + const BasicBlock* SrcBB) {
>> +
>> + const SwitchInst* SI = dyn_cast<SwitchInst>(SrcBB->getTerminator());
>> + if (SI&& UnswitchedVals.count(SI)) {
>> + // Don't clone a totally simplified switch.
>> + if (isa<Constant>(SI->getCondition()))
>> + return;
>> + Value* I = VMap.lookup(SI);
>> + assert(I&& "All instructions that are in SrcBB must be in VMap.");
>> + UnswitchedVals[cast<SwitchInst>(I)] = UnswitchedVals[SI];
>> + }
>> +}
>> +
>> /// isTrivialLoopExitBlock - Check to see if all paths from BB exit the
>> /// loop with no side effects (including infinite loops).
>> ///
>> @@ -378,14 +423,25 @@
>> // Check to see if a successor of the switch is guaranteed to go to the
>> // latch block or exit through a one exit block without having any
>> // side-effects. If so, determine the value of Cond that causes it to do
>> - // this. Note that we can't trivially unswitch on the default case.
>> - for (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i)
>> - if ((LoopExitBB = isTrivialLoopExitBlock(currentLoop,
>> + // this.
>> + // Note that we can't trivially unswitch on the default case or
>> + // on already unswitched cases.
>> + for (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i) {
>> + BasicBlock* LoopExitCandidate;
>> + if ((LoopExitCandidate = isTrivialLoopExitBlock(currentLoop,
>> SI->getSuccessor(i)))) {
>> // Okay, we found a trivial case, remember the value that is trivial.
>> - if (Val) *Val = SI->getCaseValue(i);
>> + ConstantInt* CaseVal = SI->getCaseValue(i);
>> +
>> + // Check that it was not unswitched before, since already unswitched
>> + // trivial vals are looks trivial too.
>> + if (UnswitchedVals[SI].count(CaseVal))
>> + continue;
>> + LoopExitBB = LoopExitCandidate;
>> + if (Val) *Val = CaseVal;
>> break;
>> }
>> + }
>> }
>>
>> // If we didn't find a single unique LoopExit block, or if the loop exit block
>> @@ -447,8 +503,14 @@
>> // expansion, and the number of basic blocks, to avoid loops with
>> // large numbers of branches which cause loop unswitching to go crazy.
>> // This is a very ad-hoc heuristic.
>> - if (Metrics.NumInsts> Threshold ||
>> - Metrics.NumBlocks * 5> Threshold ||
>> +
>> + unsigned NumUnswitched =
>> + (NumSwitches + NumBranches) + 1 /*take in account current iteration*/;
>> +
>> + unsigned NumInsts = Metrics.NumInsts * NumUnswitched;
>> + unsigned NumBlocks = Metrics.NumBlocks * NumUnswitched;
>> +
>> + if (NumInsts> Threshold || NumBlocks * 5> Threshold ||
>> Metrics.containsIndirectBr || Metrics.isRecursive) {
>> DEBUG(dbgs()<< "NOT unswitching loop %"
>> << currentLoop->getHeader()->getName()<< ", cost too high:"
>> @@ -620,6 +682,12 @@
>> ValueToValueMapTy VMap;
>> for (unsigned i = 0, e = LoopBlocks.size(); i != e; ++i) {
>> BasicBlock *NewBB = CloneBasicBlock(LoopBlocks[i], VMap, ".us", F);
>> +
>> + // Inherit simplified switches info for NewBB
>> + // We needn't pass NewBB since its instructions are already contained
>> + // inside the VMap.
>> + CloneUnswitchedVals(VMap, LoopBlocks[i]);
>> +
>> NewBlocks.push_back(NewBB);
>> VMap[LoopBlocks[i]] = NewBB; // Keep the BB mapping.
>> LPM->cloneBasicBlockSimpleAnalysis(LoopBlocks[i], NewBB, L);
>> @@ -945,6 +1013,9 @@
>> BasicBlock *Switch = SI->getParent();
>> BasicBlock *SISucc = SI->getSuccessor(DeadCase);
>> BasicBlock *Latch = L->getLoopLatch();
>> +
>> + UnswitchedVals[SI].insert(Val);
>> +
>> if (!SI->findCaseDest(SISucc)) continue; // Edge is critical.
>> // If the DeadCase successor dominates the loop latch, then the
>> // transformation isn't safe since it will delete the sole predecessor edge
>>
>> Added: llvm/trunk/test/Transforms/LoopUnswitch/2011-11-18-SimpleSwitch.ll
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopUnswitch/2011-11-18-SimpleSwitch.ll?rev=146578&view=auto
>> ==============================================================================
>> --- llvm/trunk/test/Transforms/LoopUnswitch/2011-11-18-SimpleSwitch.ll (added)
>> +++ llvm/trunk/test/Transforms/LoopUnswitch/2011-11-18-SimpleSwitch.ll Wed Dec 14 13:19:17 2011
>> @@ -0,0 +1,91 @@
>> +; RUN: opt -loop-unswitch -disable-output -stats -info-output-file -< %s | FileCheck --check-prefix=STATS %s
>> +; RUN: opt -S -loop-unswitch -verify-loop-info -verify-dom-info %s | FileCheck %s
>> +
>> +; STATS: 1 loop-simplify - Number of pre-header or exit blocks inserted
>> +; STATS: 2 loop-unswitch - Number of switches unswitched
>> +
>> +; CHECK: %1 = icmp eq i32 %c, 1
>> +; CHECK-NEXT: br i1 %1, label %.split.us, label %..split_crit_edge
>> +
>> +; CHECK: ..split_crit_edge: ; preds = %0
>> +; CHECK-NEXT: br label %.split
>> +
>> +; CHECK: .split.us: ; preds = %0
>> +; CHECK-NEXT: br label %loop_begin.us
>> +
>> +; CHECK: loop_begin.us: ; preds = %loop_begin.backedge.us, %.split.us
>> +; CHECK-NEXT: %var_val.us = load i32* %var
>> +; CHECK-NEXT: switch i32 1, label %default.us-lcssa.us [
>> +; CHECK-NEXT: i32 1, label %inc.us
>> +
>> +; CHECK: inc.us: ; preds = %loop_begin.us
>> +; CHECK-NEXT: call void @incf() noreturn nounwind
>> +; CHECK-NEXT: br label %loop_begin.backedge.us
>> +
>> +; CHECK: .split: ; preds = %..split_crit_edge
>> +; CHECK-NEXT: %2 = icmp eq i32 %c, 2
>> +; CHECK-NEXT: br i1 %2, label %.split.split.us, label %.split..split.split_crit_edge
>> +
>> +; CHECK: .split..split.split_crit_edge: ; preds = %.split
>> +; CHECK-NEXT: br label %.split.split
>> +
>> +; CHECK: .split.split.us: ; preds = %.split
>> +; CHECK-NEXT: br label %loop_begin.us1
>> +
>> +; CHECK: loop_begin.us1: ; preds = %loop_begin.backedge.us5, %.split.split.us
>> +; CHECK-NEXT: %var_val.us2 = load i32* %var
>> +; CHECK-NEXT: switch i32 2, label %default.us-lcssa.us-lcssa.us [
>> +; CHECK-NEXT: i32 1, label %inc.us3
>> +; CHECK-NEXT: i32 2, label %dec.us4
>> +; CHECK-NEXT: ]
>> +
>> +; CHECK: dec.us4: ; preds = %loop_begin.us1
>> +; CHECK-NEXT: call void @decf() noreturn nounwind
>> +; CHECK-NEXT: br label %loop_begin.backedge.us5
>> +
>> +; CHECK: .split.split: ; preds = %.split..split.split_crit_edge
>> +; CHECK-NEXT: br label %loop_begin
>> +
>> +; CHECK: loop_begin: ; preds = %loop_begin.backedge, %.split.split
>> +; CHECK-NEXT: %var_val = load i32* %var
>> +; CHECK-NEXT: switch i32 %c, label %default.us-lcssa.us-lcssa [
>> +; CHECK-NEXT: i32 1, label %inc
>> +; CHECK-NEXT: i32 2, label %dec
>> +; CHECK-NEXT: ]
>> +
>> +; CHECK: inc: ; preds = %loop_begin
>> +; CHECK-NEXT: br i1 true, label %us-unreachable.us-lcssa, label %inc.split
>> +
>> +; CHECK: dec: ; preds = %loop_begin
>> +; CHECK-NEXT: br i1 true, label %us-unreachable6, label %dec.split
>> +
>> +define i32 @test(i32* %var) {
>> + %mem = alloca i32
>> + store i32 2, i32* %mem
>> + %c = load i32* %mem
>> +
>> + br label %loop_begin
>> +
>> +loop_begin:
>> +
>> + %var_val = load i32* %var
>> +
>> + switch i32 %c, label %default [
>> + i32 1, label %inc
>> + i32 2, label %dec
>> + ]
>> +
>> +inc:
>> + call void @incf() noreturn nounwind
>> + br label %loop_begin
>> +dec:
>> + call void @decf() noreturn nounwind
>> + br label %loop_begin
>> +default:
>> + br label %loop_exit
>> +loop_exit:
>> + ret i32 0
>> +}
>> +
>> +declare void @incf() noreturn
>> +declare void @decf() noreturn
>>
>> Added: llvm/trunk/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches-Threshold.ll
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches-Threshold.ll?rev=146578&view=auto
>> ==============================================================================
>> --- llvm/trunk/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches-Threshold.ll (added)
>> +++ llvm/trunk/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches-Threshold.ll Wed Dec 14 13:19:17 2011
>> @@ -0,0 +1,84 @@
>> +; RUN: opt -loop-unswitch -loop-unswitch-threshold 30 -disable-output -stats -info-output-file -< %s | FileCheck --check-prefix=STATS %s
>> +; RUN: opt -S -loop-unswitch -loop-unswitch-threshold 30 -verify-loop-info -verify-dom-info %s | FileCheck %s
>> +
>> +; STATS: 1 loop-simplify - Number of pre-header or exit blocks inserted
>> +; STATS: 1 loop-unswitch - Number of switches unswitched
>> +
>> +; ModuleID = '../llvm/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches.ll'
>> +
>> +; CHECK: %1 = icmp eq i32 %c, 1
>> +; CHECK-NEXT: br i1 %1, label %.split.us, label %..split_crit_edge
>> +
>> +; CHECK: ..split_crit_edge: ; preds = %0
>> +; CHECK-NEXT: br label %.split
>> +
>> +; CHECK: .split.us: ; preds = %0
>> +; CHECK-NEXT: br label %loop_begin.us
>> +
>> +; CHECK: loop_begin.us: ; preds = %loop_begin.backedge.us, %.split.us
>> +; CHECK: switch i32 1, label %second_switch.us [
>> +; CHECK-NEXT: i32 1, label %inc.us
>> +
>> +; CHECK: inc.us: ; preds = %second_switch.us, %loop_begin.us
>> +; CHECK-NEXT: call void @incf() noreturn nounwind
>> +; CHECK-NEXT: br label %loop_begin.backedge.us
>> +
>> +; CHECK: second_switch.us: ; preds = %loop_begin.us
>> +; CHECK-NEXT: switch i32 %d, label %default.us [
>> +; CHECK-NEXT: i32 1, label %inc.us
>> +; CHECK-NEXT: ]
>> +
>> +; CHECK: .split: ; preds = %..split_crit_edge
>> +; CHECK-NEXT: br label %loop_begin
>> +
>> +; CHECK: loop_begin: ; preds = %loop_begin.backedge, %.split
>> +; CHECK: switch i32 %c, label %second_switch [
>> +; CHECK-NEXT: i32 1, label %loop_begin.inc_crit_edge
>> +; CHECK-NEXT: ]
>> +
>> +; CHECK: loop_begin.inc_crit_edge: ; preds = %loop_begin
>> +; CHECK-NEXT: br i1 true, label %us-unreachable, label %inc
>> +
>> +; CHECK: second_switch: ; preds = %loop_begin
>> +; CHECK-NEXT: switch i32 %d, label %default [
>> +; CHECK-NEXT: i32 1, label %inc
>> +; CHECK-NEXT: ]
>> +
>> +; CHECK: inc: ; preds = %loop_begin.inc_crit_edge, %second_switch
>> +; CHECK-NEXT: call void @incf() noreturn nounwind
>> +; CHECK-NEXT: br label %loop_begin.backedge
>> +
>> +define i32 @test(i32* %var) {
>> + %mem = alloca i32
>> + store i32 2, i32* %mem
>> + %c = load i32* %mem
>> + %d = load i32* %mem
>> +
>> + br label %loop_begin
>> +
>> +loop_begin:
>> +
>> + %var_val = load i32* %var
>> +
>> + switch i32 %c, label %second_switch [
>> + i32 1, label %inc
>> + ]
>> +
>> +second_switch:
>> + switch i32 %d, label %default [
>> + i32 1, label %inc
>> + ]
>> +
>> +inc:
>> + call void @incf() noreturn nounwind
>> + br label %loop_begin
>> +
>> +default:
>> + br label %loop_begin
>> +
>> +loop_exit:
>> + ret i32 0
>> +}
>> +
>> +declare void @incf() noreturn
>> +declare void @decf() noreturn
>>
>> Added: llvm/trunk/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches.ll
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches.ll?rev=146578&view=auto
>> ==============================================================================
>> --- llvm/trunk/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches.ll (added)
>> +++ llvm/trunk/test/Transforms/LoopUnswitch/2011-11-18-TwoSwitches.ll Wed Dec 14 13:19:17 2011
>> @@ -0,0 +1,138 @@
>> +; RUN: opt -loop-unswitch -loop-unswitch-threshold 1000 -disable-output -stats -info-output-file -< %s | FileCheck --check-prefix=STATS %s
>> +; RUN: opt -S -loop-unswitch -loop-unswitch-threshold 1000 -verify-loop-info -verify-dom-info %s | FileCheck %s
>> +
>> +; STATS: 1 loop-simplify - Number of pre-header or exit blocks inserted
>> +; STATS: 3 loop-unswitch - Number of switches unswitched
>> +
>> +; CHECK: %1 = icmp eq i32 %c, 1
>> +; CHECK-NEXT: br i1 %1, label %.split.us, label %..split_crit_edge
>> +
>> +; CHECK: ..split_crit_edge: ; preds = %0
>> +; CHECK-NEXT: br label %.split
>> +
>> +; CHECK: .split.us: ; preds = %0
>> +; CHECK-NEXT: %2 = icmp eq i32 %d, 1
>> +; CHECK-NEXT: br i1 %2, label %.split.us.split.us, label %.split.us..split.us.split_crit_edge
>> +
>> +; CHECK: .split.us..split.us.split_crit_edge: ; preds = %.split.us
>> +; CHECK-NEXT: br label %.split.us.split
>> +
>> +; CHECK: .split.us.split.us: ; preds = %.split.us
>> +; CHECK-NEXT: br label %loop_begin.us.us
>> +
>> +; CHECK: loop_begin.us.us: ; preds = %loop_begin.backedge.us.us, %.split.us.split.us
>> +; CHECK-NEXT: %var_val.us.us = load i32* %var
>> +; CHECK-NEXT: switch i32 1, label %second_switch.us.us [
>> +; CHECK-NEXT: i32 1, label %inc.us.us
>> +
>> +; CHECK: inc.us.us: ; preds = %second_switch.us.us, %loop_begin.us.us
>> +; CHECK-NEXT: call void @incf() noreturn nounwind
>> +; CHECK-NEXT: br label %loop_begin.backedge.us.us
>> +
>> +; CHECK: second_switch.us.us: ; preds = %loop_begin.us.us
>> +; CHECK-NEXT: switch i32 1, label %default.us.us [
>> +; CHECK-NEXT: i32 1, label %inc.us.us
>> +
>> +; CHECK: .split.us.split: ; preds = %.split.us..split.us.split_crit_edge
>> +; CHECK-NEXT: br label %loop_begin.us
>> +
>> +; CHECK: loop_begin.us: ; preds = %loop_begin.backedge.us, %.split.us.split
>> +; CHECK-NEXT: %var_val.us = load i32* %var
>> +; CHECK-NEXT: switch i32 1, label %second_switch.us [
>> +; CHECK-NEXT: i32 1, label %inc.us
>> +
>> +; CHECK: inc.us: ; preds = %second_switch.us.inc.us_crit_edge, %loop_begin.us
>> +; CHECK-NEXT: call void @incf() noreturn nounwind
>> +; CHECK-NEXT: br label %loop_begin.backedge.us
>> +
>> +; CHECK: second_switch.us: ; preds = %loop_begin.us
>> +; CHECK-NEXT: switch i32 %d, label %default.us [
>> +; CHECK-NEXT: i32 1, label %second_switch.us.inc.us_crit_edge
>> +; CHECK-NEXT: ]
>> +
>> +; CHECK: second_switch.us.inc.us_crit_edge: ; preds = %second_switch.us
>> +; CHECK-NEXT: br i1 true, label %us-unreachable8, label %inc.us
>> +
>> +; CHECK: .split: ; preds = %..split_crit_edge
>> +; CHECK-NEXT: %3 = icmp eq i32 %d, 1
>> +; CHECK-NEXT: br i1 %3, label %.split.split.us, label %.split..split.split_crit_edge
>> +
>> +; CHECK: .split..split.split_crit_edge: ; preds = %.split
>> +; CHECK-NEXT: br label %.split.split
>> +
>> +; CHECK: .split.split.us: ; preds = %.split
>> +; CHECK-NEXT: br label %loop_begin.us1
>> +
>> +; CHECK: loop_begin.us1: ; preds = %loop_begin.backedge.us6, %.split.split.us
>> +; CHECK-NEXT: %var_val.us2 = load i32* %var
>> +; CHECK-NEXT: switch i32 %c, label %second_switch.us4 [
>> +; CHECK-NEXT: i32 1, label %loop_begin.inc_crit_edge.us
>> +; CHECK-NEXT: ]
>> +
>> +; CHECK: inc.us3: ; preds = %loop_begin.inc_crit_edge.us, %second_switch.us4
>> +; CHECK-NEXT: call void @incf() noreturn nounwind
>> +; CHECK-NEXT: br label %loop_begin.backedge.us6
>> +
>> +; CHECK: second_switch.us4: ; preds = %loop_begin.us1
>> +; CHECK-NEXT: switch i32 1, label %default.us5 [
>> +; CHECK-NEXT: i32 1, label %inc.us3
>> +; CHECK-NEXT: ]
>> +
>> +; CHECK: loop_begin.inc_crit_edge.us: ; preds = %loop_begin.us1
>> +; CHECK-NEXT: br i1 true, label %us-unreachable.us-lcssa.us, label %inc.us3
>> +
>> +; CHECK: .split.split: ; preds = %.split..split.split_crit_edge
>> +; CHECK-NEXT: br label %loop_begin
>> +
>> +; CHECK: loop_begin: ; preds = %loop_begin.backedge, %.split.split
>> +; CHECK-NEXT: %var_val = load i32* %var
>> +; CHECK-NEXT: switch i32 %c, label %second_switch [
>> +; CHECK-NEXT: i32 1, label %loop_begin.inc_crit_edge
>> +; CHECK-NEXT: ]
>> +
>> +; CHECK: loop_begin.inc_crit_edge: ; preds = %loop_begin
>> +; CHECK-NEXT: br i1 true, label %us-unreachable.us-lcssa, label %inc
>> +
>> +; CHECK: second_switch: ; preds = %loop_begin
>> +; CHECK-NEXT: switch i32 %d, label %default [
>> +; CHECK-NEXT: i32 1, label %second_switch.inc_crit_edge
>> +; CHECK-NEXT: ]
>> +
>> +; CHECK: second_switch.inc_crit_edge: ; preds = %second_switch
>> +; CHECK-NEXT: br i1 true, label %us-unreachable7, label %inc
>> +
>> +
>> +define i32 @test(i32* %var) {
>> + %mem = alloca i32
>> + store i32 2, i32* %mem
>> + %c = load i32* %mem
>> + %d = load i32* %mem
>> +
>> + br label %loop_begin
>> +
>> +loop_begin:
>> +
>> + %var_val = load i32* %var
>> +
>> + switch i32 %c, label %second_switch [
>> + i32 1, label %inc
>> + ]
>> +
>> +second_switch:
>> + switch i32 %d, label %default [
>> + i32 1, label %inc
>> + ]
>> +
>> +inc:
>> + call void @incf() noreturn nounwind
>> + br label %loop_begin
>> +
>> +default:
>> + br label %loop_begin
>> +
>> +loop_exit:
>> + ret i32 0
>> +}
>> +
>> +declare void @incf() noreturn
>> +declare void @decf() noreturn
>>
>>
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