[llvm] r261203 - [PM] Port the PostOrderFunctionAttrs pass to the new pass manager and
Xinliang David Li via llvm-commits
llvm-commits at lists.llvm.org
Thu Feb 18 13:08:21 PST 2016
On Thu, Feb 18, 2016 at 12:39 PM, Chandler Carruth <chandlerc at gmail.com>
wrote:
> On Thu, Feb 18, 2016 at 12:03 PM Xinliang David Li <xinliangli at gmail.com>
> wrote:
>
>> On Thu, Feb 18, 2016 at 3:03 AM, Chandler Carruth via llvm-commits <
>> llvm-commits at lists.llvm.org> wrote:
>>
>>> -bool PostOrderFunctionAttrs::runOnSCC(CallGraphSCC &SCC) {
>>> +PreservedAnalyses
>>> +PostOrderFunctionAttrsPass::run(LazyCallGraph::SCC &C,
>>> CGSCCAnalysisManager *AM) {
>>> + Module &M = *C.begin()->getFunction().getParent();
>>> + const ModuleAnalysisManager &MAM =
>>> + AM->getResult<ModuleAnalysisManagerCGSCCProxy>(C).getManager();
>>> + FunctionAnalysisManager &FAM =
>>> + AM->getResult<FunctionAnalysisManagerCGSCCProxy>(C).getManager();
>>> +
>>> + // FIXME: Need some way to make it more reasonable to assume that
>>> this is
>>> + // always cached.
>>> + TargetLibraryInfo &TLI =
>>> *MAM.getCachedResult<TargetLibraryAnalysis>(M);
>>> +
>>> + // We pass a lambda into functions to wire them up to the analysis
>>> manager
>>> + // for getting function analyses.
>>> + auto AARGetter = [&](Function &F) -> AAResults & {
>>> + return FAM.getResult<AAManager>(F);
>>> + };
>>> +
>>> + // Fill SCCNodes with the elements of the SCC. Also track whether
>>> there are
>>> + // any external or opt-none nodes that will prevent us from
>>> optimizing any
>>> + // part of the SCC.
>>> + SCCNodeSet SCCNodes;
>>> + bool HasUnknownCall = false;
>>> + for (LazyCallGraph::Node &N : C) {
>>> + Function &F = N.getFunction();
>>> + if (F.hasFnAttribute(Attribute::OptimizeNone)) {
>>> + // Treat any function we're trying not to optimize as if it were
>>> an
>>> + // indirect call and omit it from the node set used below.
>>> + HasUnknownCall = true;
>>> + continue;
>>> + }
>>> + // Track whether any functions in this SCC have an unknown call
>>> edge.
>>> + // Note: if this is ever a performance hit, we can common it with
>>> + // subsequent routines which also do scans over the instructions of
>>> the
>>> + // function.
>>> + if (!HasUnknownCall)
>>> + for (Instruction &I : instructions(F))
>>> + if (auto CS = CallSite(&I))
>>> + if (!CS.getCalledFunction()) {
>>> + HasUnknownCall = true;
>>> + break;
>>> + }
>>> +
>>>
>>
>> The above code does not seem to exist in the legacy implementation. Is
>> this a functional change?
>>
>
> It shouldn't be. Specifically, the legacy pass manager uses the CallGraph
> analysis rather than the LazyCallGraph analysis. These two analyses provide
> slightly different models.
>
> One aspect of the CallGraph analysis is that it puts indirect calls into
> the call graph where LazyCallGraph doesn't. As a consequence, users of
> LazyCallGraph need to scan to find them.
>
I see.
>
> The difference in the design is motivated by the fact that all the code
> using the call graph ended up scanning the instructions anyways. There was
> some discussion both on the lists and elsewhere that motivated me to
> essentially wait to find a case where it was an important optimization to
> cache the indirect calls (or calls to declared external functions, they are
> equally unanalyzable) in the graph for efficiency.
>
CallGraph basically caches the indirect callsite info in the SCC node. Is
it essential to LCG to avoid this design? From this particular case, it
seems that the it introduces additional scanning cost (per-function).
thanks,
David
>
>
>
>> Also is it possible to refactor the above and share it with the legacy
>> path?
>>
>
> I think it would make the code substantially less clear because the two
> analysis provide different models. I'd rather be able to have the code
> separate and separately commented precisely to help us ask these kinds of
> questions. =]
>
>
>>
>>
>> thanks,
>>
>> David
>>
>>
>>
>>
>>> + SCCNodes.insert(&F);
>>> + }
>>> +
>>> + bool Changed = false;
>>> + Changed |= addReadAttrs(SCCNodes, AARGetter);
>>> + Changed |= addArgumentAttrs(SCCNodes);
>>> +
>>> + // If we have no external nodes participating in the SCC, we can
>>> deduce some
>>> + // more precise attributes as well.
>>> + if (!HasUnknownCall) {
>>> + Changed |= addNoAliasAttrs(SCCNodes);
>>> + Changed |= addNonNullAttrs(SCCNodes, TLI);
>>> + Changed |= removeConvergentAttrs(SCCNodes);
>>> + Changed |= addNoRecurseAttrs(SCCNodes);
>>> + }
>>> +
>>> + return Changed ? PreservedAnalyses::none() : PreservedAnalyses::all();
>>> +}
>>> +
>>> +namespace {
>>> +struct PostOrderFunctionAttrsLegacyPass : public CallGraphSCCPass {
>>> + static char ID; // Pass identification, replacement for typeid
>>> + PostOrderFunctionAttrsLegacyPass() : CallGraphSCCPass(ID) {
>>> +
>>> initializePostOrderFunctionAttrsLegacyPassPass(*PassRegistry::getPassRegistry());
>>> + }
>>> +
>>> + bool runOnSCC(CallGraphSCC &SCC) override;
>>> +
>>> + void getAnalysisUsage(AnalysisUsage &AU) const override {
>>> + AU.setPreservesCFG();
>>> + AU.addRequired<AssumptionCacheTracker>();
>>> + AU.addRequired<TargetLibraryInfoWrapperPass>();
>>> + addUsedAAAnalyses(AU);
>>> + CallGraphSCCPass::getAnalysisUsage(AU);
>>> + }
>>> +
>>> +private:
>>> + TargetLibraryInfo *TLI;
>>> +};
>>> +}
>>> +
>>> +char PostOrderFunctionAttrsLegacyPass::ID = 0;
>>> +INITIALIZE_PASS_BEGIN(PostOrderFunctionAttrsLegacyPass, "functionattrs",
>>> + "Deduce function attributes", false, false)
>>> +INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
>>> +INITIALIZE_PASS_DEPENDENCY(CallGraphWrapperPass)
>>> +INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
>>> +INITIALIZE_PASS_END(PostOrderFunctionAttrsLegacyPass, "functionattrs",
>>> + "Deduce function attributes", false, false)
>>> +
>>> +Pass *llvm::createPostOrderFunctionAttrsLegacyPass() { return new
>>> PostOrderFunctionAttrsLegacyPass(); }
>>> +
>>> +bool PostOrderFunctionAttrsLegacyPass::runOnSCC(CallGraphSCC &SCC) {
>>> TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
>>> bool Changed = false;
>>>
>>>
>>> Modified: llvm/trunk/lib/Transforms/IPO/IPO.cpp
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/IPO.cpp?rev=261203&r1=261202&r2=261203&view=diff
>>>
>>> ==============================================================================
>>> --- llvm/trunk/lib/Transforms/IPO/IPO.cpp (original)
>>> +++ llvm/trunk/lib/Transforms/IPO/IPO.cpp Thu Feb 18 05:03:11 2016
>>> @@ -18,6 +18,7 @@
>>> #include "llvm/InitializePasses.h"
>>> #include "llvm/IR/LegacyPassManager.h"
>>> #include "llvm/Transforms/IPO.h"
>>> +#include "llvm/Transforms/IPO/FunctionAttrs.h"
>>>
>>> using namespace llvm;
>>>
>>> @@ -41,7 +42,7 @@ void llvm::initializeIPO(PassRegistry &R
>>> initializeLowerBitSetsPass(Registry);
>>> initializeMergeFunctionsPass(Registry);
>>> initializePartialInlinerPass(Registry);
>>> - initializePostOrderFunctionAttrsPass(Registry);
>>> + initializePostOrderFunctionAttrsLegacyPassPass(Registry);
>>> initializeReversePostOrderFunctionAttrsPass(Registry);
>>> initializePruneEHPass(Registry);
>>> initializeStripDeadPrototypesLegacyPassPass(Registry);
>>> @@ -73,7 +74,7 @@ void LLVMAddDeadArgEliminationPass(LLVMP
>>> }
>>>
>>> void LLVMAddFunctionAttrsPass(LLVMPassManagerRef PM) {
>>> - unwrap(PM)->add(createPostOrderFunctionAttrsPass());
>>> + unwrap(PM)->add(createPostOrderFunctionAttrsLegacyPass());
>>> }
>>>
>>> void LLVMAddFunctionInliningPass(LLVMPassManagerRef PM) {
>>>
>>> Modified: llvm/trunk/lib/Transforms/IPO/PassManagerBuilder.cpp
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/PassManagerBuilder.cpp?rev=261203&r1=261202&r2=261203&view=diff
>>>
>>> ==============================================================================
>>> --- llvm/trunk/lib/Transforms/IPO/PassManagerBuilder.cpp (original)
>>> +++ llvm/trunk/lib/Transforms/IPO/PassManagerBuilder.cpp Thu Feb 18
>>> 05:03:11 2016
>>> @@ -31,6 +31,7 @@
>>> #include "llvm/Target/TargetMachine.h"
>>> #include "llvm/Transforms/IPO.h"
>>> #include "llvm/Transforms/IPO/ForceFunctionAttrs.h"
>>> +#include "llvm/Transforms/IPO/FunctionAttrs.h"
>>> #include "llvm/Transforms/IPO/InferFunctionAttrs.h"
>>> #include "llvm/Transforms/Scalar.h"
>>> #include "llvm/Transforms/Vectorize.h"
>>> @@ -382,7 +383,7 @@ void PassManagerBuilder::populateModuleP
>>> Inliner = nullptr;
>>> }
>>> if (!DisableUnitAtATime)
>>> - MPM.add(createPostOrderFunctionAttrsPass());
>>> + MPM.add(createPostOrderFunctionAttrsLegacyPass());
>>> if (OptLevel > 2)
>>> MPM.add(createArgumentPromotionPass()); // Scalarize uninlined fn
>>> args
>>>
>>> @@ -577,7 +578,7 @@ void PassManagerBuilder::addLTOOptimizat
>>> PM.add(createIPSCCPPass());
>>>
>>> // Now that we internalized some globals, see if we can hack on them!
>>> - PM.add(createPostOrderFunctionAttrsPass());
>>> + PM.add(createPostOrderFunctionAttrsLegacyPass());
>>> PM.add(createReversePostOrderFunctionAttrsPass());
>>> PM.add(createGlobalOptimizerPass());
>>> // Promote any localized global vars.
>>> @@ -627,7 +628,7 @@ void PassManagerBuilder::addLTOOptimizat
>>> PM.add(createScalarReplAggregatesPass());
>>>
>>> // Run a few AA driven optimizations here and now, to cleanup the
>>> code.
>>> - PM.add(createPostOrderFunctionAttrsPass()); // Add nocapture.
>>> + PM.add(createPostOrderFunctionAttrsLegacyPass()); // Add nocapture.
>>> PM.add(createGlobalsAAWrapperPass()); // IP alias analysis.
>>>
>>> PM.add(createLICMPass()); // Hoist loop invariants.
>>>
>>> Modified: llvm/trunk/test/Transforms/FunctionAttrs/readattrs.ll
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/FunctionAttrs/readattrs.ll?rev=261203&r1=261202&r2=261203&view=diff
>>>
>>> ==============================================================================
>>> --- llvm/trunk/test/Transforms/FunctionAttrs/readattrs.ll (original)
>>> +++ llvm/trunk/test/Transforms/FunctionAttrs/readattrs.ll Thu Feb 18
>>> 05:03:11 2016
>>> @@ -1,4 +1,5 @@
>>> ; RUN: opt < %s -functionattrs -S | FileCheck %s
>>> +; RUN: opt < %s -aa-pipeline=basic-aa
>>> -passes='require<targetlibinfo>,cgscc(function-attrs)' -S | FileCheck %s
>>> @x = global i32 0
>>>
>>> declare void @test1_1(i8* %x1_1, i8* readonly %y1_1, ...)
>>>
>>>
>>> _______________________________________________
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>>>
>>
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