llvm-6502/include/llvm/IR/LLVMContext.h
Hal Finkel 16fd27b2c3 Add scoped-noalias metadata
This commit adds scoped noalias metadata. The primary motivations for this
feature are:
  1. To preserve noalias function attribute information when inlining
  2. To provide the ability to model block-scope C99 restrict pointers

Neither of these two abilities are added here, only the necessary
infrastructure. In fact, there should be no change to existing functionality,
only the addition of new features. The logic that converts noalias function
parameters into this metadata during inlining will come in a follow-up commit.

What is added here is the ability to generally specify noalias memory-access
sets. Regarding the metadata, alias-analysis scopes are defined similar to TBAA
nodes:

!scope0 = metadata !{ metadata !"scope of foo()" }
!scope1 = metadata !{ metadata !"scope 1", metadata !scope0 }
!scope2 = metadata !{ metadata !"scope 2", metadata !scope0 }
!scope3 = metadata !{ metadata !"scope 2.1", metadata !scope2 }
!scope4 = metadata !{ metadata !"scope 2.2", metadata !scope2 }

Loads and stores can be tagged with an alias-analysis scope, and also, with a
noalias tag for a specific scope:

... = load %ptr1, !alias.scope !{ !scope1 }
... = load %ptr2, !alias.scope !{ !scope1, !scope2 }, !noalias !{ !scope1 }

When evaluating an aliasing query, if one of the instructions is associated
with an alias.scope id that is identical to the noalias scope associated with
the other instruction, or is a descendant (in the scope hierarchy) of the
noalias scope associated with the other instruction, then the two memory
accesses are assumed not to alias.

Note that is the first element of the scope metadata is a string, then it can
be combined accross functions and translation units. The string can be replaced
by a self-reference to create globally unqiue scope identifiers.

[Note: This overview is slightly stylized, since the metadata nodes really need
to just be numbers (!0 instead of !scope0), and the scope lists are also global
unnamed metadata.]

Existing noalias metadata in a callee is "cloned" for use by the inlined code.
This is necessary because the aliasing scopes are unique to each call site
(because of possible control dependencies on the aliasing properties). For
example, consider a function: foo(noalias a, noalias b) { *a = *b; } that gets
inlined into bar() { ... if (...) foo(a1, b1); ... if (...) foo(a2, b2); } --
now just because we know that a1 does not alias with b1 at the first call site,
and a2 does not alias with b2 at the second call site, we cannot let inlining
these functons have the metadata imply that a1 does not alias with b2.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213864 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-24 14:25:39 +00:00

197 lines
7.9 KiB
C++

//===-- llvm/LLVMContext.h - Class for managing "global" state --*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file declares LLVMContext, a container of "global" state in LLVM, such
// as the global type and constant uniquing tables.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_IR_LLVMCONTEXT_H
#define LLVM_IR_LLVMCONTEXT_H
#include "llvm-c/Core.h"
#include "llvm/Support/CBindingWrapping.h"
#include "llvm/Support/Compiler.h"
namespace llvm {
class LLVMContextImpl;
class StringRef;
class Twine;
class Instruction;
class Module;
class SMDiagnostic;
class DiagnosticInfo;
template <typename T> class SmallVectorImpl;
class Function;
class DebugLoc;
/// This is an important class for using LLVM in a threaded context. It
/// (opaquely) owns and manages the core "global" data of LLVM's core
/// infrastructure, including the type and constant uniquing tables.
/// LLVMContext itself provides no locking guarantees, so you should be careful
/// to have one context per thread.
class LLVMContext {
public:
LLVMContextImpl *const pImpl;
LLVMContext();
~LLVMContext();
// Pinned metadata names, which always have the same value. This is a
// compile-time performance optimization, not a correctness optimization.
enum {
MD_dbg = 0, // "dbg"
MD_tbaa = 1, // "tbaa"
MD_prof = 2, // "prof"
MD_fpmath = 3, // "fpmath"
MD_range = 4, // "range"
MD_tbaa_struct = 5, // "tbaa.struct"
MD_invariant_load = 6, // "invariant.load"
MD_alias_scope = 7, // "alias.scope"
MD_noalias = 8 // "noalias"
};
/// getMDKindID - Return a unique non-zero ID for the specified metadata kind.
/// This ID is uniqued across modules in the current LLVMContext.
unsigned getMDKindID(StringRef Name) const;
/// getMDKindNames - Populate client supplied SmallVector with the name for
/// custom metadata IDs registered in this LLVMContext.
void getMDKindNames(SmallVectorImpl<StringRef> &Result) const;
typedef void (*InlineAsmDiagHandlerTy)(const SMDiagnostic&, void *Context,
unsigned LocCookie);
/// Defines the type of a diagnostic handler.
/// \see LLVMContext::setDiagnosticHandler.
/// \see LLVMContext::diagnose.
typedef void (*DiagnosticHandlerTy)(const DiagnosticInfo &DI, void *Context);
/// Defines the type of a yield callback.
/// \see LLVMContext::setYieldCallback.
typedef void (*YieldCallbackTy)(LLVMContext *Context, void *OpaqueHandle);
/// setInlineAsmDiagnosticHandler - This method sets a handler that is invoked
/// when problems with inline asm are detected by the backend. The first
/// argument is a function pointer and the second is a context pointer that
/// gets passed into the DiagHandler.
///
/// LLVMContext doesn't take ownership or interpret either of these
/// pointers.
void setInlineAsmDiagnosticHandler(InlineAsmDiagHandlerTy DiagHandler,
void *DiagContext = nullptr);
/// getInlineAsmDiagnosticHandler - Return the diagnostic handler set by
/// setInlineAsmDiagnosticHandler.
InlineAsmDiagHandlerTy getInlineAsmDiagnosticHandler() const;
/// getInlineAsmDiagnosticContext - Return the diagnostic context set by
/// setInlineAsmDiagnosticHandler.
void *getInlineAsmDiagnosticContext() const;
/// setDiagnosticHandler - This method sets a handler that is invoked
/// when the backend needs to report anything to the user. The first
/// argument is a function pointer and the second is a context pointer that
/// gets passed into the DiagHandler.
///
/// LLVMContext doesn't take ownership or interpret either of these
/// pointers.
void setDiagnosticHandler(DiagnosticHandlerTy DiagHandler,
void *DiagContext = nullptr);
/// getDiagnosticHandler - Return the diagnostic handler set by
/// setDiagnosticHandler.
DiagnosticHandlerTy getDiagnosticHandler() const;
/// getDiagnosticContext - Return the diagnostic context set by
/// setDiagnosticContext.
void *getDiagnosticContext() const;
/// diagnose - Report a message to the currently installed diagnostic handler.
/// This function returns, in particular in the case of error reporting
/// (DI.Severity == RS_Error), so the caller should leave the compilation
/// process in a self-consistent state, even though the generated code
/// need not be correct.
/// The diagnostic message will be implicitly prefixed with a severity
/// keyword according to \p DI.getSeverity(), i.e., "error: "
/// for RS_Error, "warning: " for RS_Warning, and "note: " for RS_Note.
void diagnose(const DiagnosticInfo &DI);
/// \brief Registers a yield callback with the given context.
///
/// The yield callback function may be called by LLVM to transfer control back
/// to the client that invoked the LLVM compilation. This can be used to yield
/// control of the thread, or perform periodic work needed by the client.
/// There is no guaranteed frequency at which callbacks must occur; in fact,
/// the client is not guaranteed to ever receive this callback. It is at the
/// sole discretion of LLVM to do so and only if it can guarantee that
/// suspending the thread won't block any forward progress in other LLVM
/// contexts in the same process.
///
/// At a suspend point, the state of the current LLVM context is intentionally
/// undefined. No assumptions about it can or should be made. Only LLVM
/// context API calls that explicitly state that they can be used during a
/// yield callback are allowed to be used. Any other API calls into the
/// context are not supported until the yield callback function returns
/// control to LLVM. Other LLVM contexts are unaffected by this restriction.
void setYieldCallback(YieldCallbackTy Callback, void *OpaqueHandle);
/// \brief Calls the yield callback (if applicable).
///
/// This transfers control of the current thread back to the client, which may
/// suspend the current thread. Only call this method when LLVM doesn't hold
/// any global mutex or cannot block the execution in another LLVM context.
void yield();
/// emitError - Emit an error message to the currently installed error handler
/// with optional location information. This function returns, so code should
/// be prepared to drop the erroneous construct on the floor and "not crash".
/// The generated code need not be correct. The error message will be
/// implicitly prefixed with "error: " and should not end with a ".".
void emitError(unsigned LocCookie, const Twine &ErrorStr);
void emitError(const Instruction *I, const Twine &ErrorStr);
void emitError(const Twine &ErrorStr);
private:
LLVMContext(LLVMContext&) LLVM_DELETED_FUNCTION;
void operator=(LLVMContext&) LLVM_DELETED_FUNCTION;
/// addModule - Register a module as being instantiated in this context. If
/// the context is deleted, the module will be deleted as well.
void addModule(Module*);
/// removeModule - Unregister a module from this context.
void removeModule(Module*);
// Module needs access to the add/removeModule methods.
friend class Module;
};
/// getGlobalContext - Returns a global context. This is for LLVM clients that
/// only care about operating on a single thread.
extern LLVMContext &getGlobalContext();
// Create wrappers for C Binding types (see CBindingWrapping.h).
DEFINE_SIMPLE_CONVERSION_FUNCTIONS(LLVMContext, LLVMContextRef)
/* Specialized opaque context conversions.
*/
inline LLVMContext **unwrap(LLVMContextRef* Tys) {
return reinterpret_cast<LLVMContext**>(Tys);
}
inline LLVMContextRef *wrap(const LLVMContext **Tys) {
return reinterpret_cast<LLVMContextRef*>(const_cast<LLVMContext**>(Tys));
}
}
#endif