3 files changed, 44 insertions, 5 deletions

diff --git a/clang/lib/Sema/DeclSpec.cpp b/clang/lib/Sema/DeclSpec.cpp
index dd2476ec371..aa5f197b541 100644
--- a/clang/lib/Sema/DeclSpec.cpp
+++ b/clang/lib/Sema/DeclSpec.cpp
@@ -339,6 +339,7 @@ bool Declarator::isDeclarationOfFunction() const {
     case TST_decimal32:
     case TST_decimal64:
     case TST_double:
+    case TST_Accum:
     case TST_Float16:
     case TST_float128:
     case TST_enum:
@@ -510,6 +511,7 @@ const char *DeclSpec::getSpecifierName(DeclSpec::TST T,
   case DeclSpec::TST_half:        return "half";
   case DeclSpec::TST_float:       return "float";
   case DeclSpec::TST_double:      return "double";
+  case DeclSpec::TST_accum:       return "_Accum";
   case DeclSpec::TST_float16:     return "_Float16";
   case DeclSpec::TST_float128:    return "__float128";
   case DeclSpec::TST_bool:        return Policy.Bool ? "bool" : "_Bool";
@@ -1100,12 +1102,13 @@ void DeclSpec::Finish(Sema &S, const PrintingPolicy &Policy) {
     }
   }
 
-  // signed/unsigned are only valid with int/char/wchar_t.
+  // signed/unsigned are only valid with int/char/wchar_t/_Accum.
   if (TypeSpecSign != TSS_unspecified) {
     if (TypeSpecType == TST_unspecified)
       TypeSpecType = TST_int; // unsigned -> unsigned int, signed -> signed int.
-    else if (TypeSpecType != TST_int  && TypeSpecType != TST_int128 &&
-             TypeSpecType != TST_char && TypeSpecType != TST_wchar) {
+    else if (TypeSpecType != TST_int && TypeSpecType != TST_int128 &&
+             TypeSpecType != TST_char && TypeSpecType != TST_wchar &&
+             TypeSpecType != TST_accum) {
       S.Diag(TSSLoc, diag::err_invalid_sign_spec)
         << getSpecifierName((TST)TypeSpecType, Policy);
       // signed double -> double.
@@ -1120,7 +1123,8 @@ void DeclSpec::Finish(Sema &S, const PrintingPolicy &Policy) {
   case TSW_longlong: // long long int
     if (TypeSpecType == TST_unspecified)
       TypeSpecType = TST_int; // short -> short int, long long -> long long int.
-    else if (TypeSpecType != TST_int) {
+    else if (!(TypeSpecType == TST_int ||
+               (TypeSpecType == TST_accum && TypeSpecWidth != TSW_longlong))) {
       S.Diag(TSWRange.getBegin(), diag::err_invalid_width_spec)
           << (int)TypeSpecWidth << getSpecifierName((TST)TypeSpecType, Policy);
       TypeSpecType = TST_int;
@@ -1130,7 +1134,8 @@ void DeclSpec::Finish(Sema &S, const PrintingPolicy &Policy) {
   case TSW_long:  // long double, long int
     if (TypeSpecType == TST_unspecified)
       TypeSpecType = TST_int;  // long -> long int.
-    else if (TypeSpecType != TST_int && TypeSpecType != TST_double) {
+    else if (TypeSpecType != TST_int && TypeSpecType != TST_double &&
+             TypeSpecType != TST_accum) {
       S.Diag(TSWRange.getBegin(), diag::err_invalid_width_spec)
           << (int)TypeSpecWidth << getSpecifierName((TST)TypeSpecType, Policy);
       TypeSpecType = TST_int;
diff --git a/clang/lib/Sema/SemaTemplateVariadic.cpp b/clang/lib/Sema/SemaTemplateVariadic.cpp
index c58e648bb3b..dc67c8ef19a 100644
--- a/clang/lib/Sema/SemaTemplateVariadic.cpp
+++ b/clang/lib/Sema/SemaTemplateVariadic.cpp
@@ -830,6 +830,7 @@ bool Sema::containsUnexpandedParameterPacks(Declarator &D) {
   case TST_half:
   case TST_float:
   case TST_double:
+  case TST_Accum:
   case TST_Float16:
   case TST_float128:
   case TST_bool:
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index 6839dd7de21..ac85e016ba0 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -1391,6 +1391,39 @@ static QualType ConvertDeclSpecToType(TypeProcessingState &state) {
     }
     break;
   }
+  case DeclSpec::TST_accum: {
+    if (DS.getTypeSpecSign() != DeclSpec::TSS_unsigned) {
+      switch (DS.getTypeSpecWidth()) {
+        case DeclSpec::TSW_short:
+          Result = Context.ShortAccumTy;
+          break;
+        case DeclSpec::TSW_unspecified:
+          Result = Context.AccumTy;
+          break;
+        case DeclSpec::TSW_long:
+          Result = Context.LongAccumTy;
+          break;
+        case DeclSpec::TSW_longlong:
+          // Unreachable b/c this is caught in final analysis of the DeclSpec.
+          llvm_unreachable("Unable to specify long long as _Accum width");
+      }
+    } else {
+      switch (DS.getTypeSpecWidth()) {
+        case DeclSpec::TSW_short:
+          Result = Context.UnsignedShortAccumTy;
+          break;
+        case DeclSpec::TSW_unspecified:
+          Result = Context.UnsignedAccumTy;
+          break;
+        case DeclSpec::TSW_long:
+          Result = Context.UnsignedLongAccumTy;
+          break;
+        case DeclSpec::TSW_longlong:
+          llvm_unreachable("Unable to specify long long as _Accum width");
+      }
+    }
+    break;
+  }
   case DeclSpec::TST_int128:
     if (!S.Context.getTargetInfo().hasInt128Type())
       S.Diag(DS.getTypeSpecTypeLoc(), diag::err_type_unsupported)