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It includes: - location and of each safe point in machine code (identified by a label) - location of each root within the stack frame (identified by an offset), including the metadata tag provided to llvm.gcroot in the user program - size of the stack frame (for collectors which want to cheat on stack crawling :) - and eventually will include liveness It is to be populated by back-ends during code-generation. CollectorModuleMetadata aggregates this information across the entire module. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@42418 91177308-0d34-0410-b5e6-96231b3b80d8
196 lines
6.5 KiB
C++
196 lines
6.5 KiB
C++
//===-- CollectorMetadata.h - Garbage collector metadata ------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by Gordon Henriksen and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file declares the CollectorMetadata and CollectorModuleMetadata classes,
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// which are used as a communication channel from the target code generator
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// to the target garbage collector. This interface allows code generators and
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// garbage collectors to be developed independently.
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//
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// The CollectorMetadata class records the data necessary to build a type
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// accurate stack map. Roots are specified in the LLVM IR using the llvm.gcroot
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// intrinsic, which the code generator understands. The code generator records
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// the stack offset for each GC root. Safe points are generated by the code
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// generator according to the collector's declared needs (generally at function
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// calls).
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//
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// Safe points and roots are sufficient to build type-accurate stack maps. As a
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// refinement, liveness analysis calculates the set of live roots at each safe
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// point. Liveness analysis is not presently performed, so all roots are assumed
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// live.
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//
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// CollectorModuleMetadata simply collects CollectorMetadata structures for each
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// Function as it is compiled. This is necessary for collectors which must emit
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// a stack map for the entire compilation unit. CollectorMetadata outlives the
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// MachineFunction from which it is derived, so must not refer to any code
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// generator data structures.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CODEGEN_COLLECTORMETADATA_H
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#define LLVM_CODEGEN_COLLECTORMETADATA_H
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#include "llvm/Pass.h"
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#include "llvm/ADT/DenseMap.h"
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namespace llvm {
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class Constant;
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/// Creates a pass to print collector metadata.
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///
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Pass *createCollectorMetadataPrinter(std::ostream &OS);
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/// Creates a pass to destroy collector metadata.
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///
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Pass *createCollectorMetadataDeleter();
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namespace GC {
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/// PointKind - The type of a collector-safe point.
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///
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enum PointKind {
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Loop, //< Instr is a loop (backwards branch).
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Return, //< Instr is a return instruction.
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PreCall, //< Instr is a call instruction.
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PostCall //< Instr is the return address of a call.
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};
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}
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/// GCPoint - Metadata for a collector-safe point in machine code.
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///
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struct GCPoint {
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GC::PointKind Kind; //< The kind of the safe point.
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unsigned Num; //< Usually a label.
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GCPoint(GC::PointKind K, unsigned N) : Kind(K), Num(N) {}
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};
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/// GCRoot - Metadata for a pointer to an object managed by the garbage
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/// collector.
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struct GCRoot {
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int Num; //< Usually a frame index.
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int StackOffset; //< Offset from the stack pointer.
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Constant *Metadata; //< From the call to llvm.gcroot.
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GCRoot(int N, Constant *MD) : Num(N), StackOffset(-1), Metadata(MD) {}
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};
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/// CollectorMetadata - Garbage collection metadata for a function.
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///
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class CollectorMetadata {
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public:
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typedef std::vector<GCPoint>::iterator iterator;
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typedef std::vector<GCRoot>::iterator roots_iterator;
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typedef std::vector<GCRoot>::const_iterator live_iterator;
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private:
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const Function &F;
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uint64_t FrameSize;
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std::vector<GCRoot> Roots;
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std::vector<GCPoint> SafePoints;
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// FIXME: Liveness. A 2D BitVector, perhaps?
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//
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// BitVector Liveness;
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//
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// bool islive(int point, int root) =
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// Liveness[point * SafePoints.size() + root]
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//
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// The bit vector is the more compact representation where >3.2% of roots
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// are live per safe point (1.5% on 64-bit hosts).
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friend class CollectorModuleMetadata;
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CollectorMetadata(const Function &F);
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public:
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~CollectorMetadata();
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const Function &getFunction() const { return F; }
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/// addStackRoot - Registers a root that lives on the stack. Num is the
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/// stack object ID for the alloca (if the code generator is using
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/// MachineFrameInfo).
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void addStackRoot(int Num, Constant *Metadata) {
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Roots.push_back(GCRoot(Num, Metadata));
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}
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/// addSafePoint - Notes the existence of a safe point. Num is the ID of the
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/// label just prior to the safe point (if the code generator is using
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/// MachineModuleInfo).
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void addSafePoint(GC::PointKind Kind, unsigned Num) {
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SafePoints.push_back(GCPoint(Kind, Num));
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}
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/// getFrameSize/setFrameSize - Records the function's frame size.
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///
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uint64_t getFrameSize() const { return FrameSize; }
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void setFrameSize(uint64_t S) { FrameSize = S; }
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/// begin/end - Iterators for safe points.
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///
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iterator begin() { return SafePoints.begin(); }
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iterator end() { return SafePoints.end(); }
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size_t size() const { return SafePoints.size(); }
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/// roots_begin/roots_end - Iterators for all roots in the function.
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///
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roots_iterator roots_begin() { return Roots.begin(); }
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roots_iterator roots_end () { return Roots.end(); }
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size_t roots_size() const { return Roots.size(); }
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/// live_begin/live_end - Iterators for live roots at a given safe point.
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///
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live_iterator live_begin(const iterator &p) { return roots_begin(); }
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live_iterator live_end (const iterator &p) { return roots_end(); }
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size_t live_size(const iterator &p) const { return roots_size(); }
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};
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/// CollectorModuleMetadata - Garbage collection metadata for a whole module.
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///
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class CollectorModuleMetadata : public ImmutablePass {
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typedef std::vector<CollectorMetadata*> list_type;
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typedef DenseMap<const Function*,CollectorMetadata*> map_type;
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Module *Mod;
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list_type Functions;
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map_type Map;
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public:
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typedef list_type::iterator iterator;
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static char ID;
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CollectorModuleMetadata();
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~CollectorModuleMetadata();
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/// clear - Used to delete module metadata. Collector invokes this as
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/// necessary.
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void clear();
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/// begin/end - Iterators for function metadata.
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///
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iterator begin() { return Functions.begin(); }
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iterator end() { return Functions.end(); }
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/// insert - Creates metadata for a function.
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///
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CollectorMetadata& insert(const Function *F);
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/// get - Looks up existing function metadata.
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///
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CollectorMetadata* get(const Function *F) const;
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};
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}
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#endif
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