[ARM] Add __bf16 as new Bfloat16 C Type

Summary:
This patch upstreams support for a new storage only bfloat16 C type.
This type is used to implement primitive support for bfloat16 data, in
line with the Bfloat16 extension of the Armv8.6-a architecture, as
detailed here:

https://community.arm.com/developer/ip-products/processors/b/processors-ip-blog/posts/arm-architecture-developments-armv8-6-a

The bfloat type, and its properties are specified in the Arm Architecture
Reference Manual:

https://developer.arm.com/docs/ddi0487/latest/arm-architecture-reference-manual-armv8-for-armv8-a-architecture-profile

In detail this patch:
- introduces an opaque, storage-only C-type __bf16, which introduces a new bfloat IR type.

This is part of a patch series, starting with command-line and Bfloat16
assembly support. The subsequent patches will upstream intrinsics
support for BFloat16, followed by Matrix Multiplication and the
remaining Virtualization features of the armv8.6-a architecture.

The following people contributed to this patch:
- Luke Cheeseman
- Momchil Velikov
- Alexandros Lamprineas
- Luke Geeson
- Simon Tatham
- Ties Stuij

Reviewers: SjoerdMeijer, rjmccall, rsmith, liutianle, RKSimon, craig.topper, jfb, LukeGeeson, fpetrogalli

Reviewed By: SjoerdMeijer

Subscribers: labrinea, majnemer, asmith, dexonsmith, kristof.beyls, arphaman, danielkiss, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D76077

1 files changed, 7 insertions, 0 deletions

diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index d5d4993..7e76197 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -3842,6 +3842,10 @@ void Parser::ParseDeclarationSpecifiers(DeclSpec &DS,
       isInvalid = DS.SetTypeSpecType(DeclSpec::TST_half, Loc, PrevSpec,
                                      DiagID, Policy);
       break;
+    case tok::kw___bf16:
+      isInvalid = DS.SetTypeSpecType(DeclSpec::TST_BFloat16, Loc, PrevSpec,
+                                     DiagID, Policy);
+      break;
     case tok::kw_float:
       isInvalid = DS.SetTypeSpecType(DeclSpec::TST_float, Loc, PrevSpec,
                                      DiagID, Policy);
@@ -4942,6 +4946,7 @@ bool Parser::isKnownToBeTypeSpecifier(const Token &Tok) const {
   case tok::kw_char32_t:
   case tok::kw_int:
   case tok::kw__ExtInt:
+  case tok::kw___bf16:
   case tok::kw_half:
   case tok::kw_float:
   case tok::kw_double:
@@ -5023,6 +5028,7 @@ bool Parser::isTypeSpecifierQualifier() {
   case tok::kw_int:
   case tok::kw__ExtInt:
   case tok::kw_half:
+  case tok::kw___bf16:
   case tok::kw_float:
   case tok::kw_double:
   case tok::kw__Accum:
@@ -5190,6 +5196,7 @@ bool Parser::isDeclarationSpecifier(bool DisambiguatingWithExpression) {
   case tok::kw_int:
   case tok::kw__ExtInt:
   case tok::kw_half:
+  case tok::kw___bf16:
   case tok::kw_float:
   case tok::kw_double:
   case tok::kw__Accum: