[IR][BFloat] Add BFloat IR type

Summary:
The BFloat IR type is introduced to provide support for, initially, the BFloat16
datatype introduced with the Armv8.6 architecture (optional from Armv8.2
onwards). It has an 8-bit exponent and a 7-bit mantissa and behaves like an IEEE
754 floating point IR type.

This is part of a patch series upstreaming Armv8.6 features. Subsequent patches
will upstream intrinsics support and C-lang support for BFloat.

Reviewers: SjoerdMeijer, rjmccall, rsmith, liutianle, RKSimon, craig.topper, jfb, LukeGeeson, sdesmalen, deadalnix, ctetreau

Subscribers: hiraditya, llvm-commits, danielkiss, arphaman, kristof.beyls, dexonsmith

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D78190

1 files changed, 10 insertions, 2 deletions

diff --git a/llvm/lib/AsmParser/LLLexer.cpp b/llvm/lib/AsmParser/LLLexer.cpp
index 06631fc..eb85ef7 100644
--- a/llvm/lib/AsmParser/LLLexer.cpp
+++ b/llvm/lib/AsmParser/LLLexer.cpp
@@ -820,6 +820,7 @@ lltok::Kind LLLexer::LexIdentifier() {
 
   TYPEKEYWORD("void",      Type::getVoidTy(Context));
   TYPEKEYWORD("half",      Type::getHalfTy(Context));
+  TYPEKEYWORD("bfloat",    Type::getBFloatTy(Context));
   TYPEKEYWORD("float",     Type::getFloatTy(Context));
   TYPEKEYWORD("double",    Type::getDoubleTy(Context));
   TYPEKEYWORD("x86_fp80",  Type::getX86_FP80Ty(Context));
@@ -985,11 +986,13 @@ lltok::Kind LLLexer::LexIdentifier() {
 ///    HexFP128Constant  0xL[0-9A-Fa-f]+
 ///    HexPPC128Constant 0xM[0-9A-Fa-f]+
 ///    HexHalfConstant   0xH[0-9A-Fa-f]+
+///    HexBFloatConstant 0xR[0-9A-Fa-f]+
 lltok::Kind LLLexer::Lex0x() {
   CurPtr = TokStart + 2;
 
   char Kind;
-  if ((CurPtr[0] >= 'K' && CurPtr[0] <= 'M') || CurPtr[0] == 'H') {
+  if ((CurPtr[0] >= 'K' && CurPtr[0] <= 'M') || CurPtr[0] == 'H' ||
+      CurPtr[0] == 'R') {
     Kind = *CurPtr++;
   } else {
     Kind = 'J';
@@ -1007,7 +1010,7 @@ lltok::Kind LLLexer::Lex0x() {
   if (Kind == 'J') {
     // HexFPConstant - Floating point constant represented in IEEE format as a
     // hexadecimal number for when exponential notation is not precise enough.
-    // Half, Float, and double only.
+    // Half, BFloat, Float, and double only.
     APFloatVal = APFloat(APFloat::IEEEdouble(),
                          APInt(64, HexIntToVal(TokStart + 2, CurPtr)));
     return lltok::APFloat;
@@ -1035,6 +1038,11 @@ lltok::Kind LLLexer::Lex0x() {
     APFloatVal = APFloat(APFloat::IEEEhalf(),
                          APInt(16,HexIntToVal(TokStart+3, CurPtr)));
     return lltok::APFloat;
+  case 'R':
+    // Brain floating point
+    APFloatVal = APFloat(APFloat::BFloat(),
+                         APInt(16, HexIntToVal(TokStart + 3, CurPtr)));
+    return lltok::APFloat;
   }
 }