blob: 8bd747f03970d21a8a619e474d08a8c34a760ab6 [file] [log] [blame]
//===- LibCallSemantics.h - Describe library semantics --------------------===//
// The LLVM Compiler Infrastructure
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
// This file defines interfaces that can be used to describe language specific
// runtime library interfaces (e.g. libc, libm, etc) to LLVM optimizers.
#include "llvm/Analysis/AliasAnalysis.h"
namespace llvm {
/// LibCallLocationInfo - This struct describes a set of memory locations that
/// are accessed by libcalls. Identification of a location is doing with a
/// simple callback function.
/// For example, the LibCallInfo may be set up to model the behavior of
/// standard libm functions. The location that they may be interested in is
/// an abstract location that represents errno for the current target. In
/// this case, a location for errno is anything such that the predicate
/// returns true. On Mac OS X, this predicate would return true if the
/// pointer is the result of a call to "__error()".
/// Locations can also be defined in a constant-sensitive way. For example,
/// it is possible to define a location that returns true iff it is passed
/// into the call as a specific argument. This is useful for modeling things
/// like "printf", which can store to memory, but only through pointers passed
/// with a '%n' constraint.
struct LibCallLocationInfo {
// TODO: Flags: isContextSensitive etc.
/// isLocation - Return a LocResult if the specified pointer refers to this
/// location for the specified call site. This returns "Yes" if we can tell
/// that the pointer *does definitely* refer to the location, "No" if we can
/// tell that the location *definitely does not* refer to the location, and
/// returns "Unknown" if we cannot tell for certain.
enum LocResult {
Yes, No, Unknown
LocResult (*isLocation)(ImmutableCallSite CS,
const AliasAnalysis::Location &Loc);
/// LibCallFunctionInfo - Each record in the array of FunctionInfo structs
/// records the behavior of one libcall that is known by the optimizer. This
/// captures things like the side effects of the call. Side effects are
/// modeled both universally (in the readnone/readonly) sense, but also
/// potentially against a set of abstract locations defined by the optimizer.
/// This allows an optimizer to define that some libcall (e.g. sqrt) is
/// side-effect free except that it might modify errno (thus, the call is
/// *not* universally readonly). Or it might say that the side effects
/// are unknown other than to say that errno is not modified.
struct LibCallFunctionInfo {
/// Name - This is the name of the libcall this describes.
const char *Name;
/// TODO: Constant folding function: Constant* vector -> Constant*.
/// UniversalBehavior - This captures the absolute mod/ref behavior without
/// any specific context knowledge. For example, if the function is known
/// to be readonly, this would be set to 'ref'. If known to be readnone,
/// this is set to NoModRef.
AliasAnalysis::ModRefResult UniversalBehavior;
/// LocationMRInfo - This pair captures info about whether a specific
/// location is modified or referenced by a libcall.
struct LocationMRInfo {
/// LocationID - ID # of the accessed location or ~0U for array end.
unsigned LocationID;
/// MRInfo - Mod/Ref info for this location.
AliasAnalysis::ModRefResult MRInfo;
/// DetailsType - Indicate the sense of the LocationDetails array. This
/// controls how the LocationDetails array is interpreted.
enum {
/// DoesOnly - If DetailsType is set to DoesOnly, then we know that the
/// *only* mod/ref behavior of this function is captured by the
/// LocationDetails array. If we are trying to say that 'sqrt' can only
/// modify errno, we'd have the {errnoloc,mod} in the LocationDetails
/// array and have DetailsType set to DoesOnly.
/// DoesNot - If DetailsType is set to DoesNot, then the sense of the
/// LocationDetails array is completely inverted. This means that we *do
/// not* know everything about the side effects of this libcall, but we do
/// know things that the libcall cannot do. This is useful for complex
/// functions like 'ctime' which have crazy mod/ref behavior, but are
/// known to never read or write errno. In this case, we'd have
/// {errnoloc,modref} in the LocationDetails array and DetailsType would
/// be set to DoesNot, indicating that ctime does not read or write the
/// errno location.
} DetailsType;
/// LocationDetails - This is a pointer to an array of LocationMRInfo
/// structs which indicates the behavior of the libcall w.r.t. specific
/// locations. For example, if this libcall is known to only modify
/// 'errno', it would have a LocationDetails array with the errno ID and
/// 'mod' in it. See the DetailsType field for how this is interpreted.
/// In the "DoesOnly" case, this information is 'may' information for: there
/// is no guarantee that the specified side effect actually does happen,
/// just that it could. In the "DoesNot" case, this is 'must not' info.
/// If this pointer is null, no details are known.
const LocationMRInfo *LocationDetails;
/// LibCallInfo - Abstract interface to query about library call information.
/// Instances of this class return known information about some set of
/// libcalls.
class LibCallInfo {
// Implementation details of this object, private.
mutable void *Impl;
mutable const LibCallLocationInfo *Locations;
mutable unsigned NumLocations;
LibCallInfo() : Impl(nullptr), Locations(nullptr), NumLocations(0) {}
virtual ~LibCallInfo();
// Accessor Methods: Efficient access to contained data.
/// getLocationInfo - Return information about the specified LocationID.
const LibCallLocationInfo &getLocationInfo(unsigned LocID) const;
/// getFunctionInfo - Return the LibCallFunctionInfo object corresponding to
/// the specified function if we have it. If not, return null.
const LibCallFunctionInfo *getFunctionInfo(const Function *F) const;
// Implementation Methods: Subclasses should implement these.
/// getLocationInfo - Return descriptors for the locations referenced by
/// this set of libcalls.
virtual unsigned getLocationInfo(const LibCallLocationInfo *&Array) const {
return 0;
/// getFunctionInfoArray - Return an array of descriptors that describe the
/// set of libcalls represented by this LibCallInfo object. This array is
/// terminated by an entry with a NULL name.
virtual const LibCallFunctionInfo *getFunctionInfoArray() const = 0;
} // end namespace llvm