TargetLibraryInfo: Introduce wcslen

[MatzeB]

Summary

wcslen is part of the C99 and C++98 standards.

• This introduces the function to TargetLibraryInfo.
• Also set attributes for wcslen in llvm::inferLibFuncAttributes().

This especially helps eliminating unnecessary exception landing pads in the std::wstring constructor which is often inlined.

[MatzeB]

• Add missing wcslen declaration to unittests/Analysis/TargetLibraryInfoTest.cpp

[andrew.w.kaylor]

Looks good to me

include/llvm/Analysis/TargetLibraryInfo.def

 TLI_DEFINE_ENUM_INTERNAL(vsnprintf)
 TLI_DEFINE_STRING_INTERNAL("vsnprintf")
 /// int vsprintf(char *s, const char *format, va_list ap);
 TLI_DEFINE_ENUM_INTERNAL(vsprintf)
 TLI_DEFINE_STRING_INTERNAL("vsprintf")
 /// int vsscanf(const char *s, const char *format, va_list arg);
 TLI_DEFINE_ENUM_INTERNAL(vsscanf)
 TLI_DEFINE_STRING_INTERNAL("vsscanf")
+/// size_t wcslen (const wchar_t* wcs);
+TLI_DEFINE_ENUM_INTERNAL(wcslen)
+TLI_DEFINE_STRING_INTERNAL("wcslen")
 /// ssize_t write(int fildes, const void *buf, size_t nbyte);
 TLI_DEFINE_ENUM_INTERNAL(write)
 TLI_DEFINE_STRING_INTERNAL("write")
 
 #undef TLI_DEFINE_ENUM_INTERNAL
 #undef TLI_DEFINE_STRING_INTERNAL
 #endif  // One of TLI_DEFINE_ENUM/STRING are defined.
 
 #undef TLI_DEFINE_ENUM
 #undef TLI_DEFINE_STRING

lib/Analysis/TargetLibraryInfo.cpp

return (NumParams == 2 && FTy.getReturnType() == FTy.getParamType(1) &&
             FTy.getParamType(0) == PCharTy &&
             FTy.getParamType(1) == SizeTTy);
 
   case LibFunc_posix_memalign:
     return (NumParams == 3 && FTy.getReturnType()->isIntegerTy(32) &&
             FTy.getParamType(0)->isPointerTy() &&
             FTy.getParamType(1) == SizeTTy && FTy.getParamType(2) == SizeTTy);
 
+  case LibFunc_wcslen:
+    return (NumParams == 1 && FTy.getParamType(0)->isPointerTy() &&
+            FTy.getReturnType()->isIntegerTy());
+
   case LibFunc::NumLibFuncs:
     break;
   }
 
   llvm_unreachable("Invalid libfunc");
 }
 
 bool TargetLibraryInfoImpl::getLibFunc(const Function &FDecl,

lib/Transforms/Utils/BuildLibCalls.cpp

 bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
   LibFunc TheLibFunc;
   if (!(TLI.getLibFunc(F, TheLibFunc) && TLI.has(TheLibFunc)))
     return false;
 
   bool Changed = false;
   switch (TheLibFunc) {
   case LibFunc_strlen:
+  case LibFunc_wcslen:
     Changed |= setOnlyReadsMemory(F);
     Changed |= setDoesNotThrow(F);
     Changed |= setDoesNotCapture(F, 0);
     return Changed;
   case LibFunc_strchr:
   case LibFunc_strrchr:
     Changed |= setOnlyReadsMemory(F);
     Changed |= setDoesNotThrow(F);