[Builtins] Treat `bcmp` as a builtin.

[courbet]

Summary

This makes it consistent with memcmp and __builtin_bcmp.

Also see the discussion in https://reviews.llvm.org/D56593.

[efriedma]

This looks essentially fine, but I'd like to see some basic test coverage for the changes to warnings and constant evaluation.

[courbet]

• Add tests for warnings.
• Fix signature for intrinsic.

[courbet]

• add __builtin_bcmp constant evaluation tests.

[courbet]

Update tests after constness changes.

[jyknight]

Looks reasonable to me.

[efriedma]

LGTM

[courbet]

Thanks.

include/clang/Basic/Builtins.def

 LIBBUILTIN(stpcpy, "c*c*cC*",     "f",     "string.h", ALL_GNU_LANGUAGES)
 LIBBUILTIN(stpncpy, "c*c*cC*z",   "f",     "string.h", ALL_GNU_LANGUAGES)
 LIBBUILTIN(strdup, "c*cC*",       "f",     "string.h", ALL_GNU_LANGUAGES)
 LIBBUILTIN(strndup, "c*cC*z",     "f",     "string.h", ALL_GNU_LANGUAGES)
 // POSIX strings.h
 LIBBUILTIN(index, "c*cC*i",       "f",     "strings.h", ALL_GNU_LANGUAGES)
 LIBBUILTIN(rindex, "c*cC*i",      "f",     "strings.h", ALL_GNU_LANGUAGES)
 LIBBUILTIN(bzero, "vv*z",         "f",     "strings.h", ALL_GNU_LANGUAGES)
+LIBBUILTIN(bcmp, "iv*v*z",        "f",     "strings.h", ALL_GNU_LANGUAGES)
 // In some systems str[n]casejmp is a macro that expands to _str[n]icmp.
 // We undefine then here to avoid wrong name.
 #undef strcasecmp
 #undef strncasecmp
 LIBBUILTIN(strcasecmp, "icC*cC*", "f",     "strings.h", ALL_GNU_LANGUAGES)
 LIBBUILTIN(strncasecmp, "icC*cC*z", "f",   "strings.h", ALL_GNU_LANGUAGES)
 // POSIX unistd.h
 LIBBUILTIN(_exit, "vi",           "fr",    "unistd.h", ALL_GNU_LANGUAGES)

lib/AST/Decl.cpp

unsigned FunctionDecl::getMemoryFunctionKind() const {
   case Builtin::BIstrlcat:
   case Builtin::BI__builtin___strlcat_chk:
     return Builtin::BIstrlcat;
 
   case Builtin::BI__builtin_memcmp:
   case Builtin::BImemcmp:
     return Builtin::BImemcmp;
 
+  case Builtin::BI__builtin_bcmp:
+  case Builtin::BIbcmp:
+    return Builtin::BIbcmp;
+
   case Builtin::BI__builtin_strncpy:
   case Builtin::BI__builtin___strncpy_chk:
   case Builtin::BIstrncpy:
     return Builtin::BIstrncpy;
 
   case Builtin::BI__builtin_strncmp:
   case Builtin::BIstrncmp:
     return Builtin::BIstrncmp;
if (isExternC()) {
       if (FnInfo->isStr("memset"))
         return Builtin::BImemset;
       else if (FnInfo->isStr("memcpy"))
         return Builtin::BImemcpy;
       else if (FnInfo->isStr("memmove"))
         return Builtin::BImemmove;
       else if (FnInfo->isStr("memcmp"))
         return Builtin::BImemcmp;
+      else if (FnInfo->isStr("bcmp"))
+        return Builtin::BIbcmp;
       else if (FnInfo->isStr("strncpy"))
         return Builtin::BIstrncpy;
       else if (FnInfo->isStr("strncmp"))
         return Builtin::BIstrncmp;
       else if (FnInfo->isStr("strncasecmp"))
         return Builtin::BIstrncasecmp;
       else if (FnInfo->isStr("strncat"))
         return Builtin::BIstrncat;

lib/AST/ExprConstant.cpp

case Builtin::BI__builtin_wcslen: {
     }
   }
 
   case Builtin::BIstrcmp:
   case Builtin::BIwcscmp:
   case Builtin::BIstrncmp:
   case Builtin::BIwcsncmp:
   case Builtin::BImemcmp:
+  case Builtin::BIbcmp:
   case Builtin::BIwmemcmp:
     // A call to strlen is not a constant expression.
     if (Info.getLangOpts().CPlusPlus11)
       Info.CCEDiag(E, diag::note_constexpr_invalid_function)
         << /*isConstexpr*/0 << /*isConstructor*/0
         << (std::string("'") + Info.Ctx.BuiltinInfo.getName(BuiltinOp) + "'");
     else
       Info.CCEDiag(E, diag::note_invalid_subexpr_in_const_expr);
     LLVM_FALLTHROUGH;
   case Builtin::BI__builtin_strcmp:
   case Builtin::BI__builtin_wcscmp:
   case Builtin::BI__builtin_strncmp:
   case Builtin::BI__builtin_wcsncmp:
   case Builtin::BI__builtin_memcmp:
+  case Builtin::BI__builtin_bcmp:
   case Builtin::BI__builtin_wmemcmp: {
     LValue String1, String2;
     if (!EvaluatePointer(E->getArg(0), String1, Info) ||
         !EvaluatePointer(E->getArg(1), String2, Info))
       return false;
 
     uint64_t MaxLength = uint64_t(-1);
     if (BuiltinOp != Builtin::BIstrcmp &&
if (!String1.checkNullPointerForFoldAccess(Info, E, AK_Read) ||
         !String2.checkNullPointerForFoldAccess(Info, E, AK_Read) ||
         String1.Designator.Invalid || String2.Designator.Invalid)
       return false;
 
     QualType CharTy1 = String1.Designator.getType(Info.Ctx);
     QualType CharTy2 = String2.Designator.getType(Info.Ctx);
 
     bool IsRawByte = BuiltinOp == Builtin::BImemcmp ||
-                     BuiltinOp == Builtin::BI__builtin_memcmp;
+                     BuiltinOp == Builtin::BIbcmp ||
+                     BuiltinOp == Builtin::BI__builtin_memcmp ||
+                     BuiltinOp == Builtin::BI__builtin_bcmp;
 
     assert(IsRawByte ||
            (Info.Ctx.hasSameUnqualifiedType(
                 CharTy1, E->getArg(0)->getType()->getPointeeType()) &&
             Info.Ctx.hasSameUnqualifiedType(CharTy1, CharTy2)));
 
     const auto &ReadCurElems = [&](APValue &Char1, APValue &Char2) {
       return handleLValueToRValueConversion(Info, E, CharTy1, String1, Char1) &&
if (IsRawByte) {
         if (BytesRemaining <= BytesPerElement)
           break;
         BytesRemaining -= BytesPerElement;
       }
       // Enough elements are equal to account for the memcmp limit.
       return Success(0, E);
     }
 
-    bool StopAtNull = (BuiltinOp != Builtin::BImemcmp &&
-                       BuiltinOp != Builtin::BIwmemcmp &&
-                       BuiltinOp != Builtin::BI__builtin_memcmp &&
-                       BuiltinOp != Builtin::BI__builtin_wmemcmp);
+    bool StopAtNull =
+        (BuiltinOp != Builtin::BImemcmp && BuiltinOp != Builtin::BIbcmp &&
+         BuiltinOp != Builtin::BI__builtin_bcmp &&
     bool IsWide = BuiltinOp == Builtin::BIwcscmp ||
                   BuiltinOp == Builtin::BIwcsncmp ||
                   BuiltinOp == Builtin::BIwmemcmp ||
                   BuiltinOp == Builtin::BI__builtin_wcscmp ||
                   BuiltinOp == Builtin::BI__builtin_wcsncmp ||
                   BuiltinOp == Builtin::BI__builtin_wmemcmp;
 
     for (; MaxLength; --MaxLength) {

lib/Sema/SemaChecking.cpp

if (PointeeTy == QualType())
       continue;
 
     // Always complain about dynamic classes.
     bool IsContained;
     if (const CXXRecordDecl *ContainedRD =
             getContainedDynamicClass(PointeeTy, IsContained)) {
 
       unsigned OperationType = 0;
+      const bool IsCmp = BId == Builtin::BImemcmp || BId == Builtin::BIbcmp;
       // "overwritten" if we're warning about the destination for any call
       // but memcmp; otherwise a verb appropriate to the call.
-      if (ArgIdx != 0 || BId == Builtin::BImemcmp) {
+      if (ArgIdx != 0 || IsCmp) {
         if (BId == Builtin::BImemcpy)
           OperationType = 1;
         else if(BId == Builtin::BImemmove)
           OperationType = 2;
-        else if (BId == Builtin::BImemcmp)
+        else if (IsCmp)
           OperationType = 3;
       }
 
-      DiagRuntimeBehavior(
-        Dest->getExprLoc(), Dest,
+      DiagRuntimeBehavior(Dest->getExprLoc(), Dest,
                           PDiag(diag::warn_dyn_class_memaccess)
-          << (BId == Builtin::BImemcmp ? ArgIdx + 2 : ArgIdx)
-          << FnName << IsContained << ContainedRD << OperationType
+                              << (IsCmp ? ArgIdx + 2 : ArgIdx) << FnName
+                              << IsContained << ContainedRD << OperationType
                               << Call->getCallee()->getSourceRange());
     } else if (PointeeTy.hasNonTrivialObjCLifetime() &&
              BId != Builtin::BImemset)
       DiagRuntimeBehavior(
         Dest->getExprLoc(), Dest,
         PDiag(diag::warn_arc_object_memaccess)
           << ArgIdx << FnName << PointeeTy
           << Call->getCallee()->getSourceRange());
     else if (const auto *RT = PointeeTy->getAs<RecordType>()) {