1 //===- LibCallSemantics.h - Describe library semantics --------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines interfaces that can be used to describe language specific
11 // runtime library interfaces (e.g. libc, libm, etc) to LLVM optimizers.
13 //===----------------------------------------------------------------------===//
15 #ifndef LLVM_ANALYSIS_LIBCALLSEMANTICS_H
16 #define LLVM_ANALYSIS_LIBCALLSEMANTICS_H
18 #include "llvm/Analysis/AliasAnalysis.h"
22 /// LibCallLocationInfo - This struct describes a set of memory locations that
23 /// are accessed by libcalls. Identification of a location is doing with a
24 /// simple callback function.
26 /// For example, the LibCallInfo may be set up to model the behavior of
27 /// standard libm functions. The location that they may be interested in is
28 /// an abstract location that represents errno for the current target. In
29 /// this case, a location for errno is anything such that the predicate
30 /// returns true. On Mac OS/X, this predicate would return true if the
31 /// pointer is the result of a call to "__error()".
33 /// Locations can also be defined in a constant-sensitive way. For example,
34 /// it is possible to define a location that returns true iff it is passed
35 /// into the call as a specific argument. This is useful for modeling things
36 /// like "printf", which can store to memory, but only through pointers passed
37 /// with a '%n' constraint.
39 struct LibCallLocationInfo {
40 // TODO: Flags: isContextSensitive etc.
42 /// isLocation - Return a LocResult if the specified pointer refers to this
43 /// location for the specified call site. This returns "Yes" if we can tell
44 /// that the pointer *does definitely* refer to the location, "No" if we can
45 /// tell that the location *definitely does not* refer to the location, and
46 /// returns "Unknown" if we cannot tell for certain.
50 LocResult (*isLocation)(ImmutableCallSite CS,
51 const AliasAnalysis::Location &Loc);
54 /// LibCallFunctionInfo - Each record in the array of FunctionInfo structs
55 /// records the behavior of one libcall that is known by the optimizer. This
56 /// captures things like the side effects of the call. Side effects are
57 /// modeled both universally (in the readnone/readonly) sense, but also
58 /// potentially against a set of abstract locations defined by the optimizer.
59 /// This allows an optimizer to define that some libcall (e.g. sqrt) is
60 /// side-effect free except that it might modify errno (thus, the call is
61 /// *not* universally readonly). Or it might say that the side effects
62 /// are unknown other than to say that errno is not modified.
64 struct LibCallFunctionInfo {
65 /// Name - This is the name of the libcall this describes.
68 /// TODO: Constant folding function: Constant* vector -> Constant*.
70 /// UniversalBehavior - This captures the absolute mod/ref behavior without
71 /// any specific context knowledge. For example, if the function is known
72 /// to be readonly, this would be set to 'ref'. If known to be readnone,
73 /// this is set to NoModRef.
74 AliasAnalysis::ModRefResult UniversalBehavior;
76 /// LocationMRInfo - This pair captures info about whether a specific
77 /// location is modified or referenced by a libcall.
78 struct LocationMRInfo {
79 /// LocationID - ID # of the accessed location or ~0U for array end.
81 /// MRInfo - Mod/Ref info for this location.
82 AliasAnalysis::ModRefResult MRInfo;
85 /// DetailsType - Indicate the sense of the LocationDetails array. This
86 /// controls how the LocationDetails array is interpreted.
88 /// DoesOnly - If DetailsType is set to DoesOnly, then we know that the
89 /// *only* mod/ref behavior of this function is captured by the
90 /// LocationDetails array. If we are trying to say that 'sqrt' can only
91 /// modify errno, we'd have the {errnoloc,mod} in the LocationDetails
92 /// array and have DetailsType set to DoesOnly.
95 /// DoesNot - If DetailsType is set to DoesNot, then the sense of the
96 /// LocationDetails array is completely inverted. This means that we *do
97 /// not* know everything about the side effects of this libcall, but we do
98 /// know things that the libcall cannot do. This is useful for complex
99 /// functions like 'ctime' which have crazy mod/ref behavior, but are
100 /// known to never read or write errno. In this case, we'd have
101 /// {errnoloc,modref} in the LocationDetails array and DetailsType would
102 /// be set to DoesNot, indicating that ctime does not read or write the
107 /// LocationDetails - This is a pointer to an array of LocationMRInfo
108 /// structs which indicates the behavior of the libcall w.r.t. specific
109 /// locations. For example, if this libcall is known to only modify
110 /// 'errno', it would have a LocationDetails array with the errno ID and
111 /// 'mod' in it. See the DetailsType field for how this is interpreted.
113 /// In the "DoesOnly" case, this information is 'may' information for: there
114 /// is no guarantee that the specified side effect actually does happen,
115 /// just that it could. In the "DoesNot" case, this is 'must not' info.
117 /// If this pointer is null, no details are known.
119 const LocationMRInfo *LocationDetails;
123 /// LibCallInfo - Abstract interface to query about library call information.
124 /// Instances of this class return known information about some set of
128 // Implementation details of this object, private.
130 mutable const LibCallLocationInfo *Locations;
131 mutable unsigned NumLocations;
133 LibCallInfo() : Impl(0), Locations(0), NumLocations(0) {}
134 virtual ~LibCallInfo();
136 //===------------------------------------------------------------------===//
137 // Accessor Methods: Efficient access to contained data.
138 //===------------------------------------------------------------------===//
140 /// getLocationInfo - Return information about the specified LocationID.
141 const LibCallLocationInfo &getLocationInfo(unsigned LocID) const;
144 /// getFunctionInfo - Return the LibCallFunctionInfo object corresponding to
145 /// the specified function if we have it. If not, return null.
146 const LibCallFunctionInfo *getFunctionInfo(const Function *F) const;
149 //===------------------------------------------------------------------===//
150 // Implementation Methods: Subclasses should implement these.
151 //===------------------------------------------------------------------===//
153 /// getLocationInfo - Return descriptors for the locations referenced by
154 /// this set of libcalls.
155 virtual unsigned getLocationInfo(const LibCallLocationInfo *&Array) const {
159 /// getFunctionInfoArray - Return an array of descriptors that describe the
160 /// set of libcalls represented by this LibCallInfo object. This array is
161 /// terminated by an entry with a NULL name.
162 virtual const LibCallFunctionInfo *getFunctionInfoArray() const = 0;
165 } // end namespace llvm