Add a new interface for describing the behavior of library calls. This

Currently is sufficient to describe mod/ref behavior but will hopefully
eventually be extended for other purposes.

This isn't used by anything yet.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@50820 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 231 insertions, 0 deletions

diff --git a/include/llvm/Analysis/LibCallSemantics.h b/include/llvm/Analysis/LibCallSemantics.h
new file mode 100644
index 0000000000..74e8401a1f
--- /dev/null
+++ b/include/llvm/Analysis/LibCallSemantics.h
@@ -0,0 +1,166 @@
+//===- 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.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ANALYSIS_LIBCALLSEMANTICS_H
+#define LLVM_ANALYSIS_LIBCALLSEMANTICS_H
+
+#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)(CallSite CS, const Value *Ptr, unsigned Size);
+  };
+  
+  /// 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.
+      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.
+      DoesNot
+    } 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;
+  public:
+    LibCallInfo() : Impl(0), Locations(0), 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(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
+
+#endif
diff --git a/lib/Analysis/LibCallSemantics.cpp b/lib/Analysis/LibCallSemantics.cpp
new file mode 100644
index 0000000000..29850471f7
--- /dev/null
+++ b/lib/Analysis/LibCallSemantics.cpp
@@ -0,0 +1,65 @@
+//===- LibCallSemantics.cpp - 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 implements interfaces that can be used to describe language
+// specific runtime library interfaces (e.g. libc, libm, etc) to LLVM
+// optimizers.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/LibCallSemantics.h"
+#include "llvm/ADT/StringMap.h"
+#include "llvm/Function.h"
+using namespace llvm;
+
+/// getMap - This impl pointer in ~LibCallInfo is actually a StringMap.  This
+/// helper does the cast.
+static StringMap<const LibCallFunctionInfo*> *getMap(void *Ptr) {
+  return static_cast<StringMap<const LibCallFunctionInfo*> *>(Ptr);
+}
+
+LibCallInfo::~LibCallInfo() {
+  delete getMap(Impl);
+}
+
+const LibCallLocationInfo &LibCallInfo::getLocationInfo(unsigned LocID) const {
+  // Get location info on the first call.
+  if (NumLocations == 0)
+    NumLocations = getLocationInfo(Locations);
+  
+  assert(LocID < NumLocations && "Invalid location ID!");
+  return Locations[LocID];
+}
+
+
+/// getFunctionInfo - Return the LibCallFunctionInfo object corresponding to
+/// the specified function if we have it.  If not, return null.
+const LibCallFunctionInfo *LibCallInfo::getFunctionInfo(Function *F) const {
+  StringMap<const LibCallFunctionInfo*> *Map = getMap(Impl);
+  
+  /// If this is the first time we are querying for this info, lazily construct
+  /// the StringMap to index it.
+  if (Map == 0) {
+    Impl = Map = new StringMap<const LibCallFunctionInfo*>();
+    
+    const LibCallFunctionInfo *Array = getFunctionInfoArray();
+    if (Array == 0) return 0;
+    
+    // We now have the array of entries.  Populate the StringMap.
+    for (unsigned i = 0; Array[i].Name; ++i)
+      (*Map)[Array[i].Name] = Array+i;
+  }
+  
+  // Look up this function in the string map.
+  const char *ValueName = F->getNameStart();
+  StringMap<const LibCallFunctionInfo*>::iterator I =
+  Map->find(ValueName, ValueName+F->getNameLen());
+  return I != Map->end() ? I->second : 0;
+}
+