From 2c056fffac19acac54f0dce05bb144214934b41f Mon Sep 17 00:00:00 2001 From: Michael Gottesman Date: Thu, 5 Mar 2015 23:29:03 +0000 Subject: [PATCH] [objc-arc] Extract out state specific to a ref count from the main objc arc sequence dataflow. This will allow me to separate the actual ARC queries from the meat of the dataflow algorithm. llvm-svn: 231426 --- lib/Transforms/ObjCARC/CMakeLists.txt | 1 + lib/Transforms/ObjCARC/ObjCARCOpts.cpp | 288 +------------------------ lib/Transforms/ObjCARC/PtrState.cpp | 115 ++++++++++ lib/Transforms/ObjCARC/PtrState.h | 181 ++++++++++++++++ 4 files changed, 298 insertions(+), 287 deletions(-) create mode 100644 lib/Transforms/ObjCARC/PtrState.cpp create mode 100644 lib/Transforms/ObjCARC/PtrState.h diff --git a/lib/Transforms/ObjCARC/CMakeLists.txt b/lib/Transforms/ObjCARC/CMakeLists.txt index 2adea88c8a4..fbcae29044c 100644 --- a/lib/Transforms/ObjCARC/CMakeLists.txt +++ b/lib/Transforms/ObjCARC/CMakeLists.txt @@ -9,6 +9,7 @@ add_llvm_library(LLVMObjCARCOpts DependencyAnalysis.cpp ProvenanceAnalysis.cpp ProvenanceAnalysisEvaluator.cpp + PtrState.cpp ADDITIONAL_HEADER_DIRS ${LLVM_MAIN_INCLUDE_DIR}/llvm/Transforms diff --git a/lib/Transforms/ObjCARC/ObjCARCOpts.cpp b/lib/Transforms/ObjCARC/ObjCARCOpts.cpp index 2b3498f40ac..e1ff6a12304 100644 --- a/lib/Transforms/ObjCARC/ObjCARCOpts.cpp +++ b/lib/Transforms/ObjCARC/ObjCARCOpts.cpp @@ -30,6 +30,7 @@ #include "ObjCARCAliasAnalysis.h" #include "ProvenanceAnalysis.h" #include "BlotMapVector.h" +#include "PtrState.h" #include "llvm/ADT/DenseMap.h" #include "llvm/ADT/DenseSet.h" #include "llvm/ADT/STLExtras.h" @@ -174,293 +175,6 @@ STATISTIC(NumReleasesAfterOpt, "Number of releases after optimization"); #endif -namespace { - /// \enum Sequence - /// - /// \brief A sequence of states that a pointer may go through in which an - /// objc_retain and objc_release are actually needed. - enum Sequence { - S_None, - S_Retain, ///< objc_retain(x). - S_CanRelease, ///< foo(x) -- x could possibly see a ref count decrement. - S_Use, ///< any use of x. - S_Stop, ///< like S_Release, but code motion is stopped. - S_Release, ///< objc_release(x). - S_MovableRelease ///< objc_release(x), !clang.imprecise_release. - }; - - raw_ostream &operator<<(raw_ostream &OS, const Sequence S) - LLVM_ATTRIBUTE_UNUSED; - raw_ostream &operator<<(raw_ostream &OS, const Sequence S) { - switch (S) { - case S_None: - return OS << "S_None"; - case S_Retain: - return OS << "S_Retain"; - case S_CanRelease: - return OS << "S_CanRelease"; - case S_Use: - return OS << "S_Use"; - case S_Release: - return OS << "S_Release"; - case S_MovableRelease: - return OS << "S_MovableRelease"; - case S_Stop: - return OS << "S_Stop"; - } - llvm_unreachable("Unknown sequence type."); - } -} - -static Sequence MergeSeqs(Sequence A, Sequence B, bool TopDown) { - // The easy cases. - if (A == B) - return A; - if (A == S_None || B == S_None) - return S_None; - - if (A > B) std::swap(A, B); - if (TopDown) { - // Choose the side which is further along in the sequence. - if ((A == S_Retain || A == S_CanRelease) && - (B == S_CanRelease || B == S_Use)) - return B; - } else { - // Choose the side which is further along in the sequence. - if ((A == S_Use || A == S_CanRelease) && - (B == S_Use || B == S_Release || B == S_Stop || B == S_MovableRelease)) - return A; - // If both sides are releases, choose the more conservative one. - if (A == S_Stop && (B == S_Release || B == S_MovableRelease)) - return A; - if (A == S_Release && B == S_MovableRelease) - return A; - } - - return S_None; -} - -namespace { - /// \brief Unidirectional information about either a - /// retain-decrement-use-release sequence or release-use-decrement-retain - /// reverse sequence. - struct RRInfo { - /// After an objc_retain, the reference count of the referenced - /// object is known to be positive. Similarly, before an objc_release, the - /// reference count of the referenced object is known to be positive. If - /// there are retain-release pairs in code regions where the retain count - /// is known to be positive, they can be eliminated, regardless of any side - /// effects between them. - /// - /// Also, a retain+release pair nested within another retain+release - /// pair all on the known same pointer value can be eliminated, regardless - /// of any intervening side effects. - /// - /// KnownSafe is true when either of these conditions is satisfied. - bool KnownSafe; - - /// True of the objc_release calls are all marked with the "tail" keyword. - bool IsTailCallRelease; - - /// If the Calls are objc_release calls and they all have a - /// clang.imprecise_release tag, this is the metadata tag. - MDNode *ReleaseMetadata; - - /// For a top-down sequence, the set of objc_retains or - /// objc_retainBlocks. For bottom-up, the set of objc_releases. - SmallPtrSet Calls; - - /// The set of optimal insert positions for moving calls in the opposite - /// sequence. - SmallPtrSet ReverseInsertPts; - - /// If this is true, we cannot perform code motion but can still remove - /// retain/release pairs. - bool CFGHazardAfflicted; - - RRInfo() : - KnownSafe(false), IsTailCallRelease(false), ReleaseMetadata(nullptr), - CFGHazardAfflicted(false) {} - - void clear(); - - /// Conservatively merge the two RRInfo. Returns true if a partial merge has - /// occurred, false otherwise. - bool Merge(const RRInfo &Other); - - }; -} - -void RRInfo::clear() { - KnownSafe = false; - IsTailCallRelease = false; - ReleaseMetadata = nullptr; - Calls.clear(); - ReverseInsertPts.clear(); - CFGHazardAfflicted = false; -} - -bool RRInfo::Merge(const RRInfo &Other) { - // Conservatively merge the ReleaseMetadata information. - if (ReleaseMetadata != Other.ReleaseMetadata) - ReleaseMetadata = nullptr; - - // Conservatively merge the boolean state. - KnownSafe &= Other.KnownSafe; - IsTailCallRelease &= Other.IsTailCallRelease; - CFGHazardAfflicted |= Other.CFGHazardAfflicted; - - // Merge the call sets. - Calls.insert(Other.Calls.begin(), Other.Calls.end()); - - // Merge the insert point sets. If there are any differences, - // that makes this a partial merge. - bool Partial = ReverseInsertPts.size() != Other.ReverseInsertPts.size(); - for (Instruction *Inst : Other.ReverseInsertPts) - Partial |= ReverseInsertPts.insert(Inst).second; - return Partial; -} - -namespace { - /// \brief This class summarizes several per-pointer runtime properties which - /// are propogated through the flow graph. - class PtrState { - /// True if the reference count is known to be incremented. - bool KnownPositiveRefCount; - - /// True if we've seen an opportunity for partial RR elimination, such as - /// pushing calls into a CFG triangle or into one side of a CFG diamond. - bool Partial; - - /// The current position in the sequence. - unsigned char Seq : 8; - - /// Unidirectional information about the current sequence. - RRInfo RRI; - - public: - PtrState() : KnownPositiveRefCount(false), Partial(false), - Seq(S_None) {} - - - bool IsKnownSafe() const { - return RRI.KnownSafe; - } - - void SetKnownSafe(const bool NewValue) { - RRI.KnownSafe = NewValue; - } - - bool IsTailCallRelease() const { - return RRI.IsTailCallRelease; - } - - void SetTailCallRelease(const bool NewValue) { - RRI.IsTailCallRelease = NewValue; - } - - bool IsTrackingImpreciseReleases() const { - return RRI.ReleaseMetadata != nullptr; - } - - const MDNode *GetReleaseMetadata() const { - return RRI.ReleaseMetadata; - } - - void SetReleaseMetadata(MDNode *NewValue) { - RRI.ReleaseMetadata = NewValue; - } - - bool IsCFGHazardAfflicted() const { - return RRI.CFGHazardAfflicted; - } - - void SetCFGHazardAfflicted(const bool NewValue) { - RRI.CFGHazardAfflicted = NewValue; - } - - void SetKnownPositiveRefCount() { - DEBUG(dbgs() << "Setting Known Positive.\n"); - KnownPositiveRefCount = true; - } - - void ClearKnownPositiveRefCount() { - DEBUG(dbgs() << "Clearing Known Positive.\n"); - KnownPositiveRefCount = false; - } - - bool HasKnownPositiveRefCount() const { - return KnownPositiveRefCount; - } - - void SetSeq(Sequence NewSeq) { - DEBUG(dbgs() << "Old: " << Seq << "; New: " << NewSeq << "\n"); - Seq = NewSeq; - } - - Sequence GetSeq() const { - return static_cast(Seq); - } - - void ClearSequenceProgress() { - ResetSequenceProgress(S_None); - } - - void ResetSequenceProgress(Sequence NewSeq) { - DEBUG(dbgs() << "Resetting sequence progress.\n"); - SetSeq(NewSeq); - Partial = false; - RRI.clear(); - } - - void Merge(const PtrState &Other, bool TopDown); - - void InsertCall(Instruction *I) { - RRI.Calls.insert(I); - } - - void InsertReverseInsertPt(Instruction *I) { - RRI.ReverseInsertPts.insert(I); - } - - void ClearReverseInsertPts() { - RRI.ReverseInsertPts.clear(); - } - - bool HasReverseInsertPts() const { - return !RRI.ReverseInsertPts.empty(); - } - - const RRInfo &GetRRInfo() const { - return RRI; - } - }; -} - -void -PtrState::Merge(const PtrState &Other, bool TopDown) { - Seq = MergeSeqs(GetSeq(), Other.GetSeq(), TopDown); - KnownPositiveRefCount &= Other.KnownPositiveRefCount; - - // If we're not in a sequence (anymore), drop all associated state. - if (Seq == S_None) { - Partial = false; - RRI.clear(); - } else if (Partial || Other.Partial) { - // If we're doing a merge on a path that's previously seen a partial - // merge, conservatively drop the sequence, to avoid doing partial - // RR elimination. If the branch predicates for the two merge differ, - // mixing them is unsafe. - ClearSequenceProgress(); - } else { - // Otherwise merge the other PtrState's RRInfo into our RRInfo. At this - // point, we know that currently we are not partial. Stash whether or not - // the merge operation caused us to undergo a partial merging of reverse - // insertion points. - Partial = RRI.Merge(Other.RRI); - } -} - namespace { /// \brief Per-BasicBlock state. class BBState { diff --git a/lib/Transforms/ObjCARC/PtrState.cpp b/lib/Transforms/ObjCARC/PtrState.cpp new file mode 100644 index 00000000000..02c58dd3d4a --- /dev/null +++ b/lib/Transforms/ObjCARC/PtrState.cpp @@ -0,0 +1,115 @@ +//===--- PtrState.cpp -----------------------------------------------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// + +#include "PtrState.h" + +using namespace llvm; +using namespace llvm::objcarc; + +raw_ostream &operator<<(raw_ostream &OS, const Sequence S) { + switch (S) { + case S_None: + return OS << "S_None"; + case S_Retain: + return OS << "S_Retain"; + case S_CanRelease: + return OS << "S_CanRelease"; + case S_Use: + return OS << "S_Use"; + case S_Release: + return OS << "S_Release"; + case S_MovableRelease: + return OS << "S_MovableRelease"; + case S_Stop: + return OS << "S_Stop"; + } + llvm_unreachable("Unknown sequence type."); +} + +static Sequence MergeSeqs(Sequence A, Sequence B, bool TopDown) { + // The easy cases. + if (A == B) + return A; + if (A == S_None || B == S_None) + return S_None; + + if (A > B) + std::swap(A, B); + if (TopDown) { + // Choose the side which is further along in the sequence. + if ((A == S_Retain || A == S_CanRelease) && + (B == S_CanRelease || B == S_Use)) + return B; + } else { + // Choose the side which is further along in the sequence. + if ((A == S_Use || A == S_CanRelease) && + (B == S_Use || B == S_Release || B == S_Stop || B == S_MovableRelease)) + return A; + // If both sides are releases, choose the more conservative one. + if (A == S_Stop && (B == S_Release || B == S_MovableRelease)) + return A; + if (A == S_Release && B == S_MovableRelease) + return A; + } + + return S_None; +} + +void RRInfo::clear() { + KnownSafe = false; + IsTailCallRelease = false; + ReleaseMetadata = nullptr; + Calls.clear(); + ReverseInsertPts.clear(); + CFGHazardAfflicted = false; +} + +bool RRInfo::Merge(const RRInfo &Other) { + // Conservatively merge the ReleaseMetadata information. + if (ReleaseMetadata != Other.ReleaseMetadata) + ReleaseMetadata = nullptr; + + // Conservatively merge the boolean state. + KnownSafe &= Other.KnownSafe; + IsTailCallRelease &= Other.IsTailCallRelease; + CFGHazardAfflicted |= Other.CFGHazardAfflicted; + + // Merge the call sets. + Calls.insert(Other.Calls.begin(), Other.Calls.end()); + + // Merge the insert point sets. If there are any differences, + // that makes this a partial merge. + bool Partial = ReverseInsertPts.size() != Other.ReverseInsertPts.size(); + for (Instruction *Inst : Other.ReverseInsertPts) + Partial |= ReverseInsertPts.insert(Inst).second; + return Partial; +} + +void PtrState::Merge(const PtrState &Other, bool TopDown) { + Seq = MergeSeqs(GetSeq(), Other.GetSeq(), TopDown); + KnownPositiveRefCount &= Other.KnownPositiveRefCount; + + // If we're not in a sequence (anymore), drop all associated state. + if (Seq == S_None) { + Partial = false; + RRI.clear(); + } else if (Partial || Other.Partial) { + // If we're doing a merge on a path that's previously seen a partial + // merge, conservatively drop the sequence, to avoid doing partial + // RR elimination. If the branch predicates for the two merge differ, + // mixing them is unsafe. + ClearSequenceProgress(); + } else { + // Otherwise merge the other PtrState's RRInfo into our RRInfo. At this + // point, we know that currently we are not partial. Stash whether or not + // the merge operation caused us to undergo a partial merging of reverse + // insertion points. + Partial = RRI.Merge(Other.RRI); + } +} diff --git a/lib/Transforms/ObjCARC/PtrState.h b/lib/Transforms/ObjCARC/PtrState.h new file mode 100644 index 00000000000..77825b9f40d --- /dev/null +++ b/lib/Transforms/ObjCARC/PtrState.h @@ -0,0 +1,181 @@ +//===--- PtrState.h - ARC State for a Ptr -------------------*- C++ -*-----===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file contains declarations for the ARC state associated with a ptr. It +// is only used by the ARC Sequence Dataflow computation. By separating this +// from the actual dataflow, it is easier to consider the mechanics of the ARC +// optimization separate from the actual predicates being used. +// +//===----------------------------------------------------------------------===// + +#ifndef LLVM_LIB_TRANSFORMS_OBJCARC_PTRSTATE_H +#define LLVM_LIB_TRANSFORMS_OBJCARC_PTRSTATE_H + +#include "llvm/ADT/SmallPtrSet.h" +#include "llvm/IR/Instruction.h" +#include "llvm/IR/Value.h" +#include "llvm/Support/raw_ostream.h" +#include "llvm/Support/Debug.h" + +namespace llvm { +namespace objcarc { + +/// \enum Sequence +/// +/// \brief A sequence of states that a pointer may go through in which an +/// objc_retain and objc_release are actually needed. +enum Sequence { + S_None, + S_Retain, ///< objc_retain(x). + S_CanRelease, ///< foo(x) -- x could possibly see a ref count decrement. + S_Use, ///< any use of x. + S_Stop, ///< like S_Release, but code motion is stopped. + S_Release, ///< objc_release(x). + S_MovableRelease ///< objc_release(x), !clang.imprecise_release. +}; + +raw_ostream &operator<<(raw_ostream &OS, + const Sequence S) LLVM_ATTRIBUTE_UNUSED; + +/// \brief Unidirectional information about either a +/// retain-decrement-use-release sequence or release-use-decrement-retain +/// reverse sequence. +struct RRInfo { + /// After an objc_retain, the reference count of the referenced + /// object is known to be positive. Similarly, before an objc_release, the + /// reference count of the referenced object is known to be positive. If + /// there are retain-release pairs in code regions where the retain count + /// is known to be positive, they can be eliminated, regardless of any side + /// effects between them. + /// + /// Also, a retain+release pair nested within another retain+release + /// pair all on the known same pointer value can be eliminated, regardless + /// of any intervening side effects. + /// + /// KnownSafe is true when either of these conditions is satisfied. + bool KnownSafe; + + /// True of the objc_release calls are all marked with the "tail" keyword. + bool IsTailCallRelease; + + /// If the Calls are objc_release calls and they all have a + /// clang.imprecise_release tag, this is the metadata tag. + MDNode *ReleaseMetadata; + + /// For a top-down sequence, the set of objc_retains or + /// objc_retainBlocks. For bottom-up, the set of objc_releases. + SmallPtrSet Calls; + + /// The set of optimal insert positions for moving calls in the opposite + /// sequence. + SmallPtrSet ReverseInsertPts; + + /// If this is true, we cannot perform code motion but can still remove + /// retain/release pairs. + bool CFGHazardAfflicted; + + RRInfo() + : KnownSafe(false), IsTailCallRelease(false), ReleaseMetadata(nullptr), + CFGHazardAfflicted(false) {} + + void clear(); + + /// Conservatively merge the two RRInfo. Returns true if a partial merge has + /// occurred, false otherwise. + bool Merge(const RRInfo &Other); +}; + +/// \brief This class summarizes several per-pointer runtime properties which +/// are propogated through the flow graph. +class PtrState { + /// True if the reference count is known to be incremented. + bool KnownPositiveRefCount; + + /// True if we've seen an opportunity for partial RR elimination, such as + /// pushing calls into a CFG triangle or into one side of a CFG diamond. + bool Partial; + + /// The current position in the sequence. + unsigned char Seq : 8; + + /// Unidirectional information about the current sequence. + RRInfo RRI; + +public: + PtrState() : KnownPositiveRefCount(false), Partial(false), Seq(S_None) {} + + bool IsKnownSafe() const { return RRI.KnownSafe; } + + void SetKnownSafe(const bool NewValue) { RRI.KnownSafe = NewValue; } + + bool IsTailCallRelease() const { return RRI.IsTailCallRelease; } + + void SetTailCallRelease(const bool NewValue) { + RRI.IsTailCallRelease = NewValue; + } + + bool IsTrackingImpreciseReleases() const { + return RRI.ReleaseMetadata != nullptr; + } + + const MDNode *GetReleaseMetadata() const { return RRI.ReleaseMetadata; } + + void SetReleaseMetadata(MDNode *NewValue) { RRI.ReleaseMetadata = NewValue; } + + bool IsCFGHazardAfflicted() const { return RRI.CFGHazardAfflicted; } + + void SetCFGHazardAfflicted(const bool NewValue) { + RRI.CFGHazardAfflicted = NewValue; + } + + void SetKnownPositiveRefCount() { + DEBUG(dbgs() << "Setting Known Positive.\n"); + KnownPositiveRefCount = true; + } + + void ClearKnownPositiveRefCount() { + DEBUG(dbgs() << "Clearing Known Positive.\n"); + KnownPositiveRefCount = false; + } + + bool HasKnownPositiveRefCount() const { return KnownPositiveRefCount; } + + void SetSeq(Sequence NewSeq) { + DEBUG(dbgs() << "Old: " << Seq << "; New: " << NewSeq << "\n"); + Seq = NewSeq; + } + + Sequence GetSeq() const { return static_cast(Seq); } + + void ClearSequenceProgress() { ResetSequenceProgress(S_None); } + + void ResetSequenceProgress(Sequence NewSeq) { + DEBUG(dbgs() << "Resetting sequence progress.\n"); + SetSeq(NewSeq); + Partial = false; + RRI.clear(); + } + + void Merge(const PtrState &Other, bool TopDown); + + void InsertCall(Instruction *I) { RRI.Calls.insert(I); } + + void InsertReverseInsertPt(Instruction *I) { RRI.ReverseInsertPts.insert(I); } + + void ClearReverseInsertPts() { RRI.ReverseInsertPts.clear(); } + + bool HasReverseInsertPts() const { return !RRI.ReverseInsertPts.empty(); } + + const RRInfo &GetRRInfo() const { return RRI; } +}; + +} // end namespace objcarc +} // end namespace llvm + +#endif