[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
Chad Rosier
mcrosier at apple.com
Tue Dec 20 11:06:37 PST 2011
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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