P0426: Make the library implementation of constexpr char_traits a little easier

by providing a memchr builtin that returns char* instead of void*.

Also add a __has_feature flag to indicate the presence of constexpr forms of
the relevant <string> functions.

llvm-svn: 292555

3 files changed, 7 insertions, 0 deletions

diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index a8512b29405..5fab58a5af9 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -5683,6 +5683,7 @@ bool PointerExprEvaluator::VisitBuiltinCallExpr(const CallExpr *E,
   case Builtin::BI__builtin_strchr:
   case Builtin::BI__builtin_wcschr:
   case Builtin::BI__builtin_memchr:
+  case Builtin::BI__builtin_char_memchr:
   case Builtin::BI__builtin_wmemchr: {
     if (!Visit(E->getArg(0)))
       return false;
@@ -5720,6 +5721,7 @@ bool PointerExprEvaluator::VisitBuiltinCallExpr(const CallExpr *E,
       // Fall through.
     case Builtin::BImemchr:
     case Builtin::BI__builtin_memchr:
+    case Builtin::BI__builtin_char_memchr:
       // memchr compares by converting both sides to unsigned char. That's also
       // correct for strchr if we get this far (to cope with plain char being
       // unsigned in the strchr case).
diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index 2ede1d46b3d..b3d02f1f51c 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -1189,6 +1189,10 @@ RValue CodeGenFunction::EmitBuiltinExpr(const FunctionDecl *FD,
     return RValue::get(Dest.getPointer());
   }
 
+  case Builtin::BI__builtin_char_memchr:
+    BuiltinID = Builtin::BI__builtin_memchr;
+    break;
+
   case Builtin::BI__builtin___memcpy_chk: {
     // fold __builtin_memcpy_chk(x, y, cst1, cst2) to memcpy iff cst1<=cst2.
     llvm::APSInt Size, DstSize;
diff --git a/clang/lib/Lex/PPMacroExpansion.cpp b/clang/lib/Lex/PPMacroExpansion.cpp
index aebebaac46a..de166c75e2c 100644
--- a/clang/lib/Lex/PPMacroExpansion.cpp
+++ b/clang/lib/Lex/PPMacroExpansion.cpp
@@ -1183,6 +1183,7 @@ static bool HasFeature(const Preprocessor &PP, StringRef Feature) {
       .Case("cxx_attributes", LangOpts.CPlusPlus11)
       .Case("cxx_auto_type", LangOpts.CPlusPlus11)
       .Case("cxx_constexpr", LangOpts.CPlusPlus11)
+      .Case("cxx_constexpr_string_builtins", LangOpts.CPlusPlus11)
       .Case("cxx_decltype", LangOpts.CPlusPlus11)
       .Case("cxx_decltype_incomplete_return_types", LangOpts.CPlusPlus11)
       .Case("cxx_default_function_template_args", LangOpts.CPlusPlus11)