[llvm] r328004 - Add an analysis printer for must execute reasoning
David Blaikie via llvm-commits
llvm-commits at lists.llvm.org
Thu Mar 29 10:24:47 PDT 2018
Ah, sorry - I think I tested that first & found it was used. I forget what
the particular use was - but should be easy to reproduce & hopefully
there's some good fix for it. Happy to help with the implementation or
ideas about how to address it if you like.
On Thu, Mar 29, 2018 at 10:15 AM Philip Reames <listmail at philipreames.com>
wrote:
>
>
> On 03/28/2018 04:16 PM, David Blaikie wrote:
>
>
>
> On Tue, Mar 20, 2018 at 10:11 AM Philip Reames via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
>> Author: reames
>> Date: Tue Mar 20 10:09:21 2018
>> New Revision: 328004
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=328004&view=rev
>> Log:
>> Add an analysis printer for must execute reasoning
>>
>> Many of our loop passes make use of so called "must execute" or
>> "guaranteed to execute" facts to prove the legality of code motion. The
>> basic notion is that we know (by assumption) an instruction didn't fault at
>> it's original location, so if the location we move it to is strictly post
>> dominated by the original, then we can't have introduced a new fault.
>>
>> At the moment, the testing for this logic is somewhat adhoc and done
>> mostly through LICM. Since I'm working on that code, I want to improve the
>> testing. This patch is the first step in that direction. It doesn't
>> actually test the variant used by the loop passes - I need to move that to
>> the Analysis library first - but instead exercises an alternate
>> implementation used by SCEV. (I plan on merging both implementations.)
>>
>> Note: I'll be replacing the printing logic within this with an annotation
>> based version in the near future. Anna suggested this in review, and it
>> seems like a strictly better format.
>>
>> Differential Revision: https://reviews.llvm.org/D44524
>>
>>
>> Added:
>> llvm/trunk/lib/Analysis/MustExecute.cpp
>> llvm/trunk/test/Analysis/MustExecute/
>> llvm/trunk/test/Analysis/MustExecute/loop-header.ll
>> Modified:
>> llvm/trunk/include/llvm/Analysis/Passes.h
>> llvm/trunk/include/llvm/InitializePasses.h
>> llvm/trunk/include/llvm/LinkAllPasses.h
>> llvm/trunk/lib/Analysis/Analysis.cpp
>> llvm/trunk/lib/Analysis/CMakeLists.txt
>>
>> Modified: llvm/trunk/include/llvm/Analysis/Passes.h
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/Passes.h?rev=328004&r1=328003&r2=328004&view=diff
>>
>> ==============================================================================
>> --- llvm/trunk/include/llvm/Analysis/Passes.h (original)
>> +++ llvm/trunk/include/llvm/Analysis/Passes.h Tue Mar 20 10:09:21 2018
>> @@ -96,6 +96,14 @@ namespace llvm {
>> //
>> FunctionPass *createMemDerefPrinter();
>>
>> +
>> //===--------------------------------------------------------------------===//
>> + //
>> + // createMustExecutePrinter - This pass collects information about
>> which
>> + // instructions within a loop are guaranteed to execute if the loop
>> header is
>> + // entered and prints it with -analyze.
>> + //
>> + FunctionPass *createMustExecutePrinter();
>> +
>> }
>>
>> #endif
>>
>> Modified: llvm/trunk/include/llvm/InitializePasses.h
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/InitializePasses.h?rev=328004&r1=328003&r2=328004&view=diff
>>
>> ==============================================================================
>> --- llvm/trunk/include/llvm/InitializePasses.h (original)
>> +++ llvm/trunk/include/llvm/InitializePasses.h Tue Mar 20 10:09:21 2018
>> @@ -268,6 +268,7 @@ void initializeMergedLoadStoreMotionLega
>> void initializeMetaRenamerPass(PassRegistry&);
>> void initializeModuleDebugInfoPrinterPass(PassRegistry&);
>> void initializeModuleSummaryIndexWrapperPassPass(PassRegistry&);
>> +void initializeMustExecutePrinterPass(PassRegistry&);
>> void initializeNameAnonGlobalLegacyPassPass(PassRegistry&);
>> void initializeNaryReassociateLegacyPassPass(PassRegistry&);
>> void initializeNewGVNLegacyPassPass(PassRegistry&);
>>
>> Modified: llvm/trunk/include/llvm/LinkAllPasses.h
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/LinkAllPasses.h?rev=328004&r1=328003&r2=328004&view=diff
>>
>> ==============================================================================
>> --- llvm/trunk/include/llvm/LinkAllPasses.h (original)
>> +++ llvm/trunk/include/llvm/LinkAllPasses.h Tue Mar 20 10:09:21 2018
>> @@ -207,6 +207,7 @@ namespace {
>> (void) llvm::createRewriteSymbolsPass();
>> (void) llvm::createStraightLineStrengthReducePass();
>> (void) llvm::createMemDerefPrinter();
>> + (void) llvm::createMustExecutePrinter();
>> (void) llvm::createFloat2IntPass();
>> (void) llvm::createEliminateAvailableExternallyPass();
>> (void) llvm::createScalarizeMaskedMemIntrinPass();
>>
>> Modified: llvm/trunk/lib/Analysis/Analysis.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/Analysis.cpp?rev=328004&r1=328003&r2=328004&view=diff
>>
>> ==============================================================================
>> --- llvm/trunk/lib/Analysis/Analysis.cpp (original)
>> +++ llvm/trunk/lib/Analysis/Analysis.cpp Tue Mar 20 10:09:21 2018
>> @@ -65,6 +65,7 @@ void llvm::initializeAnalysis(PassRegist
>> initializeMemoryDependenceWrapperPassPass(Registry);
>> initializeModuleDebugInfoPrinterPass(Registry);
>> initializeModuleSummaryIndexWrapperPassPass(Registry);
>> + initializeMustExecutePrinterPass(Registry);
>> initializeObjCARCAAWrapperPassPass(Registry);
>> initializeOptimizationRemarkEmitterWrapperPassPass(Registry);
>> initializePostDominatorTreeWrapperPassPass(Registry);
>>
>> Modified: llvm/trunk/lib/Analysis/CMakeLists.txt
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/CMakeLists.txt?rev=328004&r1=328003&r2=328004&view=diff
>>
>> ==============================================================================
>> --- llvm/trunk/lib/Analysis/CMakeLists.txt (original)
>> +++ llvm/trunk/lib/Analysis/CMakeLists.txt Tue Mar 20 10:09:21 2018
>> @@ -58,6 +58,7 @@ add_llvm_library(LLVMAnalysis
>> MemorySSAUpdater.cpp
>> ModuleDebugInfoPrinter.cpp
>> ModuleSummaryAnalysis.cpp
>> + MustExecute.cpp
>> ObjCARCAliasAnalysis.cpp
>> ObjCARCAnalysisUtils.cpp
>> ObjCARCInstKind.cpp
>>
>> Added: llvm/trunk/lib/Analysis/MustExecute.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/MustExecute.cpp?rev=328004&view=auto
>>
>> ==============================================================================
>> --- llvm/trunk/lib/Analysis/MustExecute.cpp (added)
>> +++ llvm/trunk/lib/Analysis/MustExecute.cpp Tue Mar 20 10:09:21 2018
>> @@ -0,0 +1,102 @@
>> +//===- MustExecute.cpp - Printer for isGuaranteedToExecute
>> ----------------===//
>> +//
>> +// The LLVM Compiler Infrastructure
>> +//
>> +// This file is distributed under the University of Illinois Open Source
>> +// License. See LICENSE.TXT for details.
>> +//
>>
>> +//===----------------------------------------------------------------------===//
>> +
>> +#include "llvm/Analysis/LoopInfo.h"
>> +#include "llvm/Analysis/Passes.h"
>> +#include "llvm/Analysis/ValueTracking.h"
>> +#include "llvm/IR/DataLayout.h"
>> +#include "llvm/IR/InstIterator.h"
>> +#include "llvm/IR/LLVMContext.h"
>> +#include "llvm/IR/Module.h"
>> +#include "llvm/Support/ErrorHandling.h"
>> +#include "llvm/Support/raw_ostream.h"
>> +#include "llvm/Transforms/Utils/LoopUtils.h"
>>
>
> This looks like a circular/invalid dependency? Transforms depend on
> Analysis, not the other way around?
>
> Would be great to get this fixed - happy to help, if you've some ideas.
>
> Moving the whole LoopUtils isn't immediately possible, its implementation
> depends on BasicBlockUtils. (& also many of these utilities seem more for
> mutation, which isn't relevant to Analysis - so maybe it needs to be split
> up?)
>
> I think this is just a stale header include. I'm building to confirm now
> and if so will remove it.
>
>
>
>> +using namespace llvm;
>> +
>> +namespace {
>> + struct MustExecutePrinter : public FunctionPass {
>> + DenseMap<Value*, SmallVector<Loop*, 4> > MustExec;
>> + SmallVector<Value *, 4> Ordering;
>> +
>> + static char ID; // Pass identification, replacement for typeid
>> + MustExecutePrinter() : FunctionPass(ID) {
>> + initializeMustExecutePrinterPass(*PassRegistry::getPassRegistry());
>> + }
>> + void getAnalysisUsage(AnalysisUsage &AU) const override {
>> + AU.setPreservesAll();
>> + AU.addRequired<DominatorTreeWrapperPass>();
>> + AU.addRequired<LoopInfoWrapperPass>();
>> + }
>> + bool runOnFunction(Function &F) override;
>> + void print(raw_ostream &OS, const Module * = nullptr) const override;
>> + void releaseMemory() override {
>> + MustExec.clear();
>> + Ordering.clear();
>> + }
>> + };
>> +}
>> +
>> +char MustExecutePrinter::ID = 0;
>> +INITIALIZE_PASS_BEGIN(MustExecutePrinter, "print-mustexecute",
>> + "Instructions which execute on loop entry", false,
>> true)
>> +INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
>> +INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
>> +INITIALIZE_PASS_END(MustExecutePrinter, "print-mustexecute",
>> + "Instructions which execute on loop entry", false,
>> true)
>> +
>> +FunctionPass *llvm::createMustExecutePrinter() {
>> + return new MustExecutePrinter();
>> +}
>> +
>> +bool isMustExecuteIn(Instruction &I, Loop *L, DominatorTree *DT) {
>> + // TODO: move loop specific code to analysis
>> + //LoopSafetyInfo LSI;
>> + //computeLoopSafetyInfo(&LSI, L);
>> + //return isGuaranteedToExecute(I, DT, L, &LSI);
>> + return isGuaranteedToExecuteForEveryIteration(&I, L);
>> +}
>> +
>> +bool MustExecutePrinter::runOnFunction(Function &F) {
>> + auto &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
>> + auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
>> + for (auto &I: instructions(F)) {
>> + Loop *L = LI.getLoopFor(I.getParent());
>> + while (L) {
>> + if (isMustExecuteIn(I, L, &DT)) {
>> + if (!MustExec.count(&I))
>> + Ordering.push_back(&I);
>> + MustExec[&I].push_back(L);
>> + }
>> + L = L->getParentLoop();
>> + };
>> + }
>> + return false;
>> +}
>> +
>> +void MustExecutePrinter::print(raw_ostream &OS, const Module *M) const {
>> + OS << "The following are guaranteed to execute (for the respective
>> loops):\n";
>> + for (Value *V: Ordering) {
>> + V->printAsOperand(OS);
>> + auto NumLoops = MustExec.lookup(V).size();
>> + if (NumLoops > 1)
>> + OS << "\t(mustexec in " << NumLoops << " loops: ";
>> + else
>> + OS << "\t(mustexec in: ";
>> +
>> + bool first = true;
>> + for (const Loop *L : MustExec.lookup(V)) {
>> + if (!first)
>> + OS << ", ";
>> + first = false;
>> + OS << L->getHeader()->getName();
>> + }
>> + OS << ")\n";
>> + }
>> + OS << "\n";
>> +}
>>
>> Added: llvm/trunk/test/Analysis/MustExecute/loop-header.ll
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/MustExecute/loop-header.ll?rev=328004&view=auto
>>
>> ==============================================================================
>> --- llvm/trunk/test/Analysis/MustExecute/loop-header.ll (added)
>> +++ llvm/trunk/test/Analysis/MustExecute/loop-header.ll Tue Mar 20
>> 10:09:21 2018
>> @@ -0,0 +1,80 @@
>> +; RUN: opt -analyze -print-mustexecute %s
>> +
>> +; CHECK: Printing analysis 'Instructions which execute on loop entry'
>> for function 'header_with_icf':
>> +; CHECK: The following are guaranteed to execute (for the respective
>> loops):
>> +; CHECK: %iv = phi i32 [ 0, %entry ], [ %iv.next, %loop ] (mustexec
>> in: loop)
>> +; CHECK: %v = load i32, i32* %p (mustexec in: loop)
>> +; CHECK: call void @maythrow_and_use(i32 %v) (mustexec in: loop)
>> +; CHECK-NOT: add
>> +define i1 @header_with_icf(i32* noalias %p, i32 %high) {
>> +entry:
>> + br label %loop
>> +
>> +loop:
>> + %iv = phi i32 [0, %entry], [%iv.next, %loop]
>> + %v = load i32, i32* %p
>> + call void @maythrow_and_use(i32 %v)
>> + %iv.next = add nsw nuw i32 %iv, 1
>> + %exit.test = icmp slt i32 %iv, %high
>> + br i1 %exit.test, label %exit, label %loop
>> +
>> +exit:
>> + ret i1 false
>> +}
>> +
>> +; CHECK: Printing analysis 'Instructions which execute on loop entry'
>> for function 'test':
>> +; CHECK: The following are guaranteed to execute (for the respective
>> loops):
>> +; CHECK: %iv = phi i32 [ 0, %entry ], [ %iv.next, %next ] (mustexec
>> in: loop)
>> +; CHECK: %v = load i32, i32* %p (mustexec in: loop)
>> +; CHECK: br label %next (mustexec in: loop)
>> +define i1 @test(i32* noalias %p, i32 %high) {
>> +entry:
>> + br label %loop
>> +
>> +loop:
>> + %iv = phi i32 [0, %entry], [%iv.next, %next]
>> + %v = load i32, i32* %p
>> + br label %next
>> +next:
>> + call void @maythrow_and_use(i32 %v)
>> + %iv.next = add nsw nuw i32 %iv, 1
>> + %exit.test = icmp slt i32 %iv, %high
>> + br i1 %exit.test, label %exit, label %loop
>> +
>> +exit:
>> + ret i1 false
>> +}
>> +
>> +; CHECK: Printing analysis 'Instructions which execute on loop entry'
>> for function 'nested':
>> +; CHECK: The following are guaranteed to execute (for the respective
>> loops):
>> +; CHECK: %iv = phi i32 [ 0, %entry ], [ %iv.next, %next ] (mustexec
>> in: loop)
>> +; CHECK: br label %inner_loop (mustexec in: loop)
>> +; FIXME: These three are also must execute for the outer loop.
>> +; CHECK: %v = load i32, i32* %p (mustexec in: inner_loop)
>> +; CHECK: %inner.test = icmp eq i32 %v, 0 (mustexec in: inner_loop)
>> +; CHECK: br i1 %inner.test, label %inner_loop, label %next (mustexec
>> in: inner_loop)
>> +define i1 @nested(i32* noalias %p, i32 %high) {
>> +entry:
>> + br label %loop
>> +
>> +loop:
>> + %iv = phi i32 [0, %entry], [%iv.next, %next]
>> + br label %inner_loop
>> +
>> +inner_loop:
>> + %v = load i32, i32* %p
>> + %inner.test = icmp eq i32 %v, 0
>> + br i1 %inner.test, label %inner_loop, label %next
>> +
>> +next:
>> + call void @maythrow_and_use(i32 %v)
>> + %iv.next = add nsw nuw i32 %iv, 1
>> + %exit.test = icmp slt i32 %iv, %high
>> + br i1 %exit.test, label %exit, label %loop
>> +
>> +exit:
>> + ret i1 false
>> +}
>> +
>> +
>> +declare void @maythrow_and_use(i32)
>>
>>
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>
>
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