6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-11-03 14:21:30 +00:00
Code Issues Projects Releases Wiki Activity

Comment and minor code cleanup for GCStrategy (NFC)

Browse Source 
Updating comments to reflect the current state of the world after my recent changes to ownership structure and generally better describe what a GCStrategy is and how it works.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224086 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Philip Reames
2014-12-12 00:49:03 +00:00
parent 6e6318f148
commit b7dfa31ac8
2 changed files with 83 additions and 58 deletions
Download Patch File Download Diff File Expand all files Collapse all files

124
include/llvm/CodeGen/GCStrategy.h
View File

@@ -13,8 +13,13 @@
// flags in a subclass's constructor, and some virtual methods can be
// overridden.
//
// When requested, the GCStrategy will be populated with data about each
// function which uses it. Specifically:
// GCStrategy is relevant for implementations using either gc.root or
// gc.statepoint based lowering strategies, but is currently focused mostly on
// options for gc.root. This will change over time.
//
// When requested by a subclass of GCStrategy, the gc.root implementation will
// populate GCModuleInfo and GCFunctionInfo with that about each Function in
// the Module that opts in to garbage collection. Specifically:
//
// - Safe points
// Garbage collection is generally only possible at certain points in code.
@@ -31,6 +36,15 @@
// This information can used to emit the metadata tables which are required by
// the target garbage collector runtime.
//
// When used with gc.statepoint, information about safepoint and roots can be
// found in the binary StackMap section after code generation. Safepoint
// placement is currently the responsibility of the frontend, though late
// insertion support is planned. gc.statepoint does not currently support
// custom stack map formats; such can be generated by parsing the standard
// stack map section if desired.
//
// The read and write barrier support can be used with either implementation.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CODEGEN_GCSTRATEGY_H
@@ -42,13 +56,6 @@
#include <string>
namespace llvm {
class GCStrategy;
/// The GC strategy registry uses all the defaults from Registry.
///
typedef Registry<GCStrategy> GCRegistry;
/// GCStrategy describes a garbage collector algorithm's code generation
/// requirements, and provides overridable hooks for those needs which cannot
/// be abstractly described. GCStrategy objects currently must be looked up
@@ -56,8 +63,8 @@ namespace llvm {
/// pass and recreated every time that pass is invalidated.
class GCStrategy {
private:
friend class GCModuleInfo;
std::string Name;
friend class GCModuleInfo;
protected:
unsigned NeededSafePoints; ///< Bitmask of required safe points.
@@ -71,65 +78,96 @@ namespace llvm {
public:
GCStrategy();
virtual ~GCStrategy() {}
/// getName - The name of the GC strategy, for debugging.
///
/// Return the name of the GC strategy. This is the value of the collector
/// name string specified on functions which use this strategy.
const std::string &getName() const { return Name; }
/// needsSafePoitns - True if safe points of any kind are required. By
// default, none are recorded.
/// By default, write barriers are replaced with simple store
/// instructions. If true, then performCustomLowering must instead lower
/// them.
bool customWriteBarrier() const { return CustomWriteBarriers; }
/// By default, read barriers are replaced with simple load
/// instructions. If true, then performCustomLowering must instead lower
/// them.
bool customReadBarrier() const { return CustomReadBarriers; }
/** @name GCRoot Specific Properties
* These properties and overrides only apply to collector strategies using
* GCRoot.
*/
///@{
/// True if safe points of any kind are required. By default, none are
/// recorded.
bool needsSafePoints() const {
return CustomSafePoints || NeededSafePoints != 0;
}
/// needsSafePoint(Kind) - True if the given kind of safe point is
// required. By default, none are recorded.
/// True if the given kind of safe point is required. By default, none are
/// recorded.
bool needsSafePoint(GC::PointKind Kind) const {
return (NeededSafePoints & 1 << Kind) != 0;
}
/// customWriteBarrier - By default, write barriers are replaced with simple
/// store instructions. If true, then
/// performCustomLowering must instead lower them.
bool customWriteBarrier() const { return CustomWriteBarriers; }
/// customReadBarrier - By default, read barriers are replaced with simple
/// load instructions. If true, then
/// performCustomLowering must instead lower them.
bool customReadBarrier() const { return CustomReadBarriers; }
/// customRoots - By default, roots are left for the code generator so it
/// can generate a stack map. If true, then
// performCustomLowering must delete them.
/// By default, roots are left for the code generator so it can generate a
/// stack map. If true, then performCustomLowering must delete them.
bool customRoots() const { return CustomRoots; }
/// customSafePoints - By default, the GC analysis will find safe
/// points according to NeededSafePoints. If true,
/// then findCustomSafePoints must create them.
/// By default, the GC analysis will find safe points according to
/// NeededSafePoints. If true, then findCustomSafePoints must create them.
bool customSafePoints() const { return CustomSafePoints; }
/// initializeRoots - If set, gcroot intrinsics should initialize their
// allocas to null before the first use. This is
// necessary for most GCs and is enabled by default.
/// If set, gcroot intrinsics should initialize their allocas to null
/// before the first use. This is necessary for most GCs and is enabled by
/// default.
bool initializeRoots() const { return InitRoots; }
/// usesMetadata - If set, appropriate metadata tables must be emitted by
/// the back-end (assembler, JIT, or otherwise).
/// If set, appropriate metadata tables must be emitted by the back-end
/// (assembler, JIT, or otherwise).
bool usesMetadata() const { return UsesMetadata; }
///@}
/// initializeCustomLowering/performCustomLowering - If any of the actions
/// are set to custom, performCustomLowering must be overriden to transform
/// the corresponding actions to LLVM IR. initializeCustomLowering is
/// optional to override. These are the only GCStrategy methods through
/// which the LLVM IR can be modified.
virtual bool initializeCustomLowering(Module &F);
virtual bool performCustomLowering(Function &F);
virtual bool findCustomSafePoints(GCFunctionInfo& FI, MachineFunction& MF);
/// which the LLVM IR can be modified. These methods apply mostly to
/// gc.root based implementations, but can be overriden to provide custom
/// barrier lowerings with gc.statepoint as well.
///@{
virtual bool initializeCustomLowering(Module &F) {
// No changes made
return false;
}
virtual bool performCustomLowering(Function &F) {
llvm_unreachable("GCStrategy subclass specified a configuration which"
"requires a custom lowering without providing one");
}
///@}
/// Called if customSafepoints returns true, used only by gc.root
/// implementations.
virtual bool findCustomSafePoints(GCFunctionInfo& FI, MachineFunction& MF) {
llvm_unreachable("GCStrategy subclass specified a configuration which"
"requests custom safepoint identification without"
"providing an implementation for such");
}
};
/// Subclasses of GCStrategy are made available for use during compilation by
/// adding them to the global GCRegistry. This can done either within the
/// LLVM source tree or via a loadable plugin. An example registeration
/// would be:
/// static GCRegistry::Add<CustomGC> X("custom-name",
/// "my custom supper fancy gc strategy");
///
/// Note that to use a custom GCMetadataPrinter w/gc.roots, you must also
/// register your GCMetadataPrinter subclass with the
/// GCMetadataPrinterRegistery as well.
typedef Registry<GCStrategy> GCRegistry;
}
#endif

13
lib/CodeGen/GCStrategy.cpp
View File

@@ -102,19 +102,6 @@ GCStrategy::GCStrategy() :
UsesMetadata(false)
{}
bool GCStrategy::initializeCustomLowering(Module &M) { return false; }
bool GCStrategy::performCustomLowering(Function &F) {
dbgs() << "gc " << getName() << " must override performCustomLowering.\n";
llvm_unreachable("must override performCustomLowering");
}
bool GCStrategy::findCustomSafePoints(GCFunctionInfo& FI, MachineFunction &F) {
dbgs() << "gc " << getName() << " must override findCustomSafePoints.\n";
llvm_unreachable(nullptr);
}
// -----------------------------------------------------------------------------
INITIALIZE_PASS_BEGIN(LowerIntrinsics, "gc-lowering", "GC Lowering",