[MLIR] Add f8E3M4 IEEE 754 type (#101230)

This PR adds `f8E3M4` type to mlir.

`f8E3M4` type  follows IEEE 754 convention

```c
f8E3M4 (IEEE 754)
- Exponent bias: 3
- Maximum stored exponent value: 6 (binary 110)
- Maximum unbiased exponent value: 6 - 3 = 3
- Minimum stored exponent value: 1 (binary 001)
- Minimum unbiased exponent value: 1 − 3 = −2
- Precision specifies the total number of bits used for the significand (mantissa), 
    including implicit leading integer bit = 4 + 1 = 5
- Follows IEEE 754 conventions for representation of special values
- Has Positive and Negative zero
- Has Positive and Negative infinity
- Has NaNs

Additional details:
- Max exp (unbiased): 3
- Min exp (unbiased): -2
- Infinities (+/-): S.111.0000
- Zeros (+/-): S.000.0000
- NaNs: S.111.{0,1}⁴ except S.111.0000
- Max normal number: S.110.1111 = +/-2^(6-3) x (1 + 15/16) = +/-2^3 x 31 x 2^(-4) = +/-15.5
- Min normal number: S.001.0000 = +/-2^(1-3) x (1 + 0) = +/-2^(-2)
- Max subnormal number: S.000.1111 = +/-2^(-2) x 15/16 = +/-2^(-2) x 15 x 2^(-4) = +/-15 x 2^(-6)
- Min subnormal number: S.000.0001 = +/-2^(-2) x 1/16 =  +/-2^(-2) x 2^(-4) = +/-2^(-6)
```

Related PRs:
- [PR-99698](https://github.com/llvm/llvm-project/pull/99698) [APFloat]
Add support for f8E3M4 IEEE 754 type
- [PR-97118](https://github.com/llvm/llvm-project/pull/97118) [MLIR] Add
f8E4M3 IEEE 754 type

mlir/include/mlir-c/BuiltinTypes.h

@@ -139,6 +139,16 @@ MLIR_CAPI_EXPORTED bool mlirTypeIsAFloat8E4M3B11FNUZ(MlirType type);
 /// context.
 MLIR_CAPI_EXPORTED MlirType mlirFloat8E4M3B11FNUZTypeGet(MlirContext ctx);
 
+/// Returns the typeID of an Float8E3M4 type.
+MLIR_CAPI_EXPORTED MlirTypeID mlirFloat8E3M4TypeGetTypeID(void);
+
+/// Checks whether the given type is an f8E3M4 type.
+MLIR_CAPI_EXPORTED bool mlirTypeIsAFloat8E3M4(MlirType type);
+
+/// Creates an f8E3M4 type in the given context. The type is owned by the
+/// context.
+MLIR_CAPI_EXPORTED MlirType mlirFloat8E3M4TypeGet(MlirContext ctx);
+
 /// Returns the typeID of an BFloat16 type.
 MLIR_CAPI_EXPORTED MlirTypeID mlirBFloat16TypeGetTypeID(void);
 

mlir/include/mlir/IR/Builders.h

@@ -66,6 +66,7 @@ public:
   FloatType getFloat8E5M2FNUZType();
   FloatType getFloat8E4M3FNUZType();
   FloatType getFloat8E4M3B11FNUZType();
+  FloatType getFloat8E3M4Type();
   FloatType getBF16Type();
   FloatType getF16Type();
   FloatType getTF32Type();

mlir/include/mlir/IR/BuiltinTypes.h

@@ -66,6 +66,7 @@ public:
   static FloatType getFloat8E5M2FNUZ(MLIRContext *ctx);
   static FloatType getFloat8E4M3FNUZ(MLIRContext *ctx);
   static FloatType getFloat8E4M3B11FNUZ(MLIRContext *ctx);
+  static FloatType getFloat8E3M4(MLIRContext *ctx);
 
   /// Methods for support type inquiry through isa, cast, and dyn_cast.
   static bool classof(Type type);
@@ -411,10 +412,11 @@ inline bool BaseMemRefType::isValidElementType(Type type) {
 }
 
 inline bool FloatType::classof(Type type) {
-  return llvm::isa<
-      Float8E5M2Type, Float8E4M3Type, Float8E4M3FNType, Float8E5M2FNUZType,
-      Float8E4M3FNUZType, Float8E4M3B11FNUZType, BFloat16Type, Float16Type,
-      FloatTF32Type, Float32Type, Float64Type, Float80Type, Float128Type>(type);
+  return llvm::isa<Float8E5M2Type, Float8E4M3Type, Float8E4M3FNType,
+                   Float8E5M2FNUZType, Float8E4M3FNUZType,
+                   Float8E4M3B11FNUZType, Float8E3M4Type, BFloat16Type,
+                   Float16Type, FloatTF32Type, Float32Type, Float64Type,
+                   Float80Type, Float128Type>(type);
 }
 
 inline FloatType FloatType::getFloat8E5M2(MLIRContext *ctx) {
@@ -441,6 +443,10 @@ inline FloatType FloatType::getFloat8E4M3B11FNUZ(MLIRContext *ctx) {
   return Float8E4M3B11FNUZType::get(ctx);
 }
 
+inline FloatType FloatType::getFloat8E3M4(MLIRContext *ctx) {
+  return Float8E3M4Type::get(ctx);
+}
+
 inline FloatType FloatType::getBF16(MLIRContext *ctx) {
   return BFloat16Type::get(ctx);
 }

mlir/include/mlir/IR/BuiltinTypes.td

@@ -213,6 +213,25 @@ def Builtin_Float8E4M3B11FNUZ : Builtin_FloatType<"Float8E4M3B11FNUZ", "f8E4M3B1
   }];
 }
 
+//===----------------------------------------------------------------------===//
+// Float8E3M4Type
+
+def Builtin_Float8E3M4 : Builtin_FloatType<"Float8E3M4", "f8E3M4"> {
+  let summary = "8-bit floating point with 3 bits exponent and 4 bit mantissa";
+  let description = [{
+    An 8-bit floating point type with 1 sign bit, 3 bits exponent and 4 bits
+    mantissa. This is not a standard type as defined by IEEE-754, but it
+    follows similar conventions with the following characteristics:
+
+      * bit encoding: S1E3M4
+      * exponent bias: 3
+      * infinities: supported with exponent set to all 1s and mantissa 0s
+      * NaNs: supported with exponent bits set to all 1s and mantissa values of
+        {0,1}⁴ except S.111.0000
+      * denormals when exponent is 0
+  }];
+}
+
 //===----------------------------------------------------------------------===//
 // BFloat16Type
 

mlir/include/mlir/IR/CommonTypeConstraints.td

@@ -342,6 +342,8 @@ def F8E4M3B11FNUZ : Type<CPred<"$_self.isFloat8E4M3B11FNUZ()">, "f8E4M3B11FNUZ t
                  BuildableType<"$_builder.getFloat8E4M3B11FNUZType()">;
 def F8E5M2FNUZ : Type<CPred<"$_self.isFloat8E5M2FNUZ()">, "f8E5M2FNUZ type">,
                  BuildableType<"$_builder.getFloat8E5M2FNUZType()">;
+def F8E3M4 : Type<CPred<"$_self.isFloat8E3M4()">, "f8E3M4 type">,
+             BuildableType<"$_builder.getFloat8E3M4Type()">;
 
 def AnyComplex : Type<CPred<"::llvm::isa<::mlir::ComplexType>($_self)">,
                       "complex-type", "::mlir::ComplexType">;

mlir/include/mlir/IR/Types.h

@@ -131,6 +131,7 @@ public:
   bool isFloat8E5M2FNUZ() const;
   bool isFloat8E4M3FNUZ() const;
   bool isFloat8E4M3B11FNUZ() const;
+  bool isFloat8E3M4() const;
   bool isBF16() const;
   bool isF16() const;
   bool isTF32() const;

mlir/lib/AsmParser/TokenKinds.def

@@ -100,6 +100,7 @@ TOK_KEYWORD(f8E4M3FN)
 TOK_KEYWORD(f8E5M2FNUZ)
 TOK_KEYWORD(f8E4M3FNUZ)
 TOK_KEYWORD(f8E4M3B11FNUZ)
+TOK_KEYWORD(f8E3M4)
 TOK_KEYWORD(f128)
 TOK_KEYWORD(false)
 TOK_KEYWORD(floordiv)

mlir/lib/AsmParser/TypeParser.cpp

@@ -45,6 +45,7 @@ OptionalParseResult Parser::parseOptionalType(Type &type) {
   case Token::kw_f8E5M2FNUZ:
   case Token::kw_f8E4M3FNUZ:
   case Token::kw_f8E4M3B11FNUZ:
+  case Token::kw_f8E3M4:
   case Token::kw_bf16:
   case Token::kw_f16:
   case Token::kw_tf32:
@@ -320,6 +321,9 @@ Type Parser::parseNonFunctionType() {
   case Token::kw_f8E4M3B11FNUZ:
     consumeToken(Token::kw_f8E4M3B11FNUZ);
     return builder.getFloat8E4M3B11FNUZType();
+  case Token::kw_f8E3M4:
+    consumeToken(Token::kw_f8E3M4);
+    return builder.getFloat8E3M4Type();
   case Token::kw_bf16:
     consumeToken(Token::kw_bf16);
     return builder.getBF16Type();

mlir/lib/Bindings/Python/IRTypes.cpp

@@ -246,6 +246,26 @@ public:
   }
 };
 
+/// Floating Point Type subclass - Float8E3M4Type.
+class PyFloat8E3M4Type : public PyConcreteType<PyFloat8E3M4Type, PyFloatType> {
+public:
+  static constexpr IsAFunctionTy isaFunction = mlirTypeIsAFloat8E3M4;
+  static constexpr GetTypeIDFunctionTy getTypeIdFunction =
+      mlirFloat8E3M4TypeGetTypeID;
+  static constexpr const char *pyClassName = "Float8E3M4Type";
+  using PyConcreteType::PyConcreteType;
+
+  static void bindDerived(ClassTy &c) {
+    c.def_static(
+        "get",
+        [](DefaultingPyMlirContext context) {
+          MlirType t = mlirFloat8E3M4TypeGet(context->get());
+          return PyFloat8E3M4Type(context->getRef(), t);
+        },
+        py::arg("context") = py::none(), "Create a float8_e3m4 type.");
+  }
+};
+
 /// Floating Point Type subclass - BF16Type.
 class PyBF16Type : public PyConcreteType<PyBF16Type, PyFloatType> {
 public:
@@ -864,6 +884,7 @@ void mlir::python::populateIRTypes(py::module &m) {
   PyFloat8E4M3FNUZType::bind(m);
   PyFloat8E4M3B11FNUZType::bind(m);
   PyFloat8E5M2FNUZType::bind(m);
+  PyFloat8E3M4Type::bind(m);
   PyBF16Type::bind(m);
   PyF16Type::bind(m);
   PyTF32Type::bind(m);

mlir/lib/CAPI/IR/BuiltinTypes.cpp

@@ -157,6 +157,18 @@ MlirType mlirFloat8E4M3B11FNUZTypeGet(MlirContext ctx) {
   return wrap(FloatType::getFloat8E4M3B11FNUZ(unwrap(ctx)));
 }
 
+MlirTypeID mlirFloat8E3M4TypeGetTypeID() {
+  return wrap(Float8E3M4Type::getTypeID());
+}
+
+bool mlirTypeIsAFloat8E3M4(MlirType type) {
+  return unwrap(type).isFloat8E3M4();
+}
+
+MlirType mlirFloat8E3M4TypeGet(MlirContext ctx) {
+  return wrap(FloatType::getFloat8E3M4(unwrap(ctx)));
+}
+
 MlirTypeID mlirBFloat16TypeGetTypeID() {
   return wrap(BFloat16Type::getTypeID());
 }

mlir/lib/Conversion/LLVMCommon/TypeConverter.cpp

@@ -249,7 +249,7 @@ Type LLVMTypeConverter::convertIntegerType(IntegerType type) const {
 Type LLVMTypeConverter::convertFloatType(FloatType type) const {
   if (type.isFloat8E5M2() || type.isFloat8E4M3() || type.isFloat8E4M3FN() ||
       type.isFloat8E5M2FNUZ() || type.isFloat8E4M3FNUZ() ||
-      type.isFloat8E4M3B11FNUZ())
+      type.isFloat8E4M3B11FNUZ() || type.isFloat8E3M4())
     return IntegerType::get(&getContext(), type.getWidth());
   return type;
 }

mlir/lib/Dialect/Arith/Transforms/EmulateUnsupportedFloats.cpp

@@ -60,6 +60,7 @@ static std::optional<FloatType> parseFloatType(MLIRContext *ctx,
       .Case("f8E4M3FN", b.getFloat8E4M3FNType())
       .Case("f8E5M2FNUZ", b.getFloat8E5M2FNUZType())
       .Case("f8E4M3FNUZ", b.getFloat8E4M3FNUZType())
+      .Case("f8E3M4", b.getFloat8E3M4Type())
       .Case("bf16", b.getBF16Type())
       .Case("f16", b.getF16Type())
       .Case("f32", b.getF32Type())

mlir/lib/IR/AsmPrinter.cpp

@@ -2581,6 +2581,7 @@ void AsmPrinter::Impl::printTypeImpl(Type type) {
       .Case<Float8E5M2FNUZType>([&](Type) { os << "f8E5M2FNUZ"; })
       .Case<Float8E4M3FNUZType>([&](Type) { os << "f8E4M3FNUZ"; })
       .Case<Float8E4M3B11FNUZType>([&](Type) { os << "f8E4M3B11FNUZ"; })
+      .Case<Float8E3M4Type>([&](Type) { os << "f8E3M4"; })
       .Case<BFloat16Type>([&](Type) { os << "bf16"; })
       .Case<Float16Type>([&](Type) { os << "f16"; })
       .Case<FloatTF32Type>([&](Type) { os << "tf32"; })

mlir/lib/IR/Builders.cpp

@@ -58,6 +58,10 @@ FloatType Builder::getFloat8E4M3B11FNUZType() {
   return FloatType::getFloat8E4M3B11FNUZ(context);
 }
 
+FloatType Builder::getFloat8E3M4Type() {
+  return FloatType::getFloat8E3M4(context);
+}
+
 FloatType Builder::getBF16Type() { return FloatType::getBF16(context); }
 
 FloatType Builder::getF16Type() { return FloatType::getF16(context); }

mlir/lib/IR/BuiltinTypes.cpp

@@ -88,8 +88,8 @@ IntegerType IntegerType::scaleElementBitwidth(unsigned scale) {
 
 unsigned FloatType::getWidth() {
   if (llvm::isa<Float8E5M2Type, Float8E4M3Type, Float8E4M3FNType,
-                Float8E5M2FNUZType, Float8E4M3FNUZType, Float8E4M3B11FNUZType>(
-          *this))
+                Float8E5M2FNUZType, Float8E4M3FNUZType, Float8E4M3B11FNUZType,
+                Float8E3M4Type>(*this))
     return 8;
   if (llvm::isa<Float16Type, BFloat16Type>(*this))
     return 16;
@@ -118,6 +118,8 @@ const llvm::fltSemantics &FloatType::getFloatSemantics() {
     return APFloat::Float8E4M3FNUZ();
   if (llvm::isa<Float8E4M3B11FNUZType>(*this))
     return APFloat::Float8E4M3B11FNUZ();
+  if (llvm::isa<Float8E3M4Type>(*this))
+    return APFloat::Float8E3M4();
   if (llvm::isa<BFloat16Type>(*this))
     return APFloat::BFloat();
   if (llvm::isa<Float16Type>(*this))

mlir/lib/IR/MLIRContext.cpp

@@ -227,6 +227,7 @@ public:
   Float8E5M2FNUZType f8E5M2FNUZTy;
   Float8E4M3FNUZType f8E4M3FNUZTy;
   Float8E4M3B11FNUZType f8E4M3B11FNUZTy;
+  Float8E3M4Type f8E3M4Ty;
   BFloat16Type bf16Ty;
   Float16Type f16Ty;
   FloatTF32Type tf32Ty;
@@ -318,6 +319,7 @@ MLIRContext::MLIRContext(const DialectRegistry &registry, Threading setting)
   impl->f8E5M2FNUZTy = TypeUniquer::get<Float8E5M2FNUZType>(this);
   impl->f8E4M3FNUZTy = TypeUniquer::get<Float8E4M3FNUZType>(this);
   impl->f8E4M3B11FNUZTy = TypeUniquer::get<Float8E4M3B11FNUZType>(this);
+  impl->f8E3M4Ty = TypeUniquer::get<Float8E3M4Type>(this);
   impl->bf16Ty = TypeUniquer::get<BFloat16Type>(this);
   impl->f16Ty = TypeUniquer::get<Float16Type>(this);
   impl->tf32Ty = TypeUniquer::get<FloatTF32Type>(this);
@@ -1029,6 +1031,9 @@ Float8E4M3FNUZType Float8E4M3FNUZType::get(MLIRContext *context) {
 Float8E4M3B11FNUZType Float8E4M3B11FNUZType::get(MLIRContext *context) {
   return context->getImpl().f8E4M3B11FNUZTy;
 }
+Float8E3M4Type Float8E3M4Type::get(MLIRContext *context) {
+  return context->getImpl().f8E3M4Ty;
+}
 BFloat16Type BFloat16Type::get(MLIRContext *context) {
   return context->getImpl().bf16Ty;
 }

mlir/lib/IR/Types.cpp

@@ -46,6 +46,7 @@ bool Type::isFloat8E4M3FNUZ() const {
 bool Type::isFloat8E4M3B11FNUZ() const {
   return llvm::isa<Float8E4M3B11FNUZType>(*this);
 }
+bool Type::isFloat8E3M4() const { return llvm::isa<Float8E3M4Type>(*this); }
 bool Type::isBF16() const { return llvm::isa<BFloat16Type>(*this); }
 bool Type::isF16() const { return llvm::isa<Float16Type>(*this); }
 bool Type::isTF32() const { return llvm::isa<FloatTF32Type>(*this); }

mlir/python/mlir/_mlir_libs/_mlir/ir.pyi

@@ -120,6 +120,7 @@ __all__ = [
     "F32Type",
     "F64Type",
     "FlatSymbolRefAttr",
+    "Float8E3M4Type",
     "Float8E4M3B11FNUZType",
     "Float8E4M3FNType",
     "Float8E4M3FNUZType",
@@ -1537,6 +1538,19 @@ class FlatSymbolRefAttr(Attribute):
         Returns the value of the FlatSymbolRef attribute as a string
         """
 
+class Float8E3M4Type(FloatType):
+    static_typeid: ClassVar[TypeID]
+    @staticmethod
+    def get(context: Optional[Context] = None) -> Float8E3M4Type:
+        """
+        Create a float8_e3m4 type.
+        """
+    @staticmethod
+    def isinstance(other: Type) -> bool: ...
+    def __init__(self, cast_from_type: Type) -> None: ...
+    @property
+    def typeid(self) -> TypeID: ...
+
 class Float8E4M3B11FNUZType(FloatType):
     static_typeid: ClassVar[TypeID]
     @staticmethod

mlir/python/mlir/extras/types.py

@@ -12,6 +12,7 @@ from ..ir import (
     F16Type,
     F32Type,
     F64Type,
+    Float8E3M4Type,
     Float8E4M3B11FNUZType,
     Float8E4M3FNType,
     Float8E4M3Type,
@@ -72,6 +73,7 @@ f8E5M2 = lambda: Float8E5M2Type.get()
 f8E4M3 = lambda: Float8E4M3Type.get()
 f8E4M3FN = lambda: Float8E4M3FNType.get()
 f8E4M3B11FNUZ = lambda: Float8E4M3B11FNUZType.get()
+f8E3M4 = lambda: Float8E3M4Type.get()
 
 none = lambda: NoneType.get()
 

mlir/test/IR/attribute.mlir

@@ -60,6 +60,10 @@ func.func @float_attrs_pass() {
     // CHECK: float_attr = 2.000000e+00 : f8E4M3B11FNUZ
     float_attr = 2. : f8E4M3B11FNUZ
   } : () -> ()
+  "test.float_attrs"() {
+    // CHECK: float_attr = 2.000000e+00 : f8E3M4
+    float_attr = 2. : f8E3M4
+  } : () -> ()
   "test.float_attrs"() {
     // CHECK: float_attr = 2.000000e+00 : f16
     float_attr = 2. : f16

mlir/test/Target/LLVMIR/llvmir.mlir

@@ -39,6 +39,9 @@ llvm.mlir.global internal constant @string_const("foobar") : !llvm.array<6 x i8>
 // CHECK: @int_global_undef = internal global i64 undef
 llvm.mlir.global internal @int_global_undef() : i64
 
+// CHECK: @f8E3M4_global_as_i8 = internal global i8 56
+llvm.mlir.global internal @f8E3M4_global_as_i8(1.5 : f8E3M4) : i8
+
 // CHECK: @f8E4M3_global_as_i8 = internal global i8 60
 llvm.mlir.global internal @f8E4M3_global_as_i8(1.5 : f8E4M3) : i8
 

mlir/test/python/ir/builtin_types.py

@@ -113,6 +113,8 @@ def testTypeIsInstance():
 def testFloatTypeSubclasses():
     ctx = Context()
     # CHECK: True
+    print(isinstance(Type.parse("f8E3M4", ctx), FloatType))
+    # CHECK: True
     print(isinstance(Type.parse("f8E4M3", ctx), FloatType))
     # CHECK: True
     print(isinstance(Type.parse("f8E4M3FN", ctx), FloatType))
@@ -231,6 +233,8 @@ def testIndexType():
 @run
 def testFloatType():
     with Context():
+        # CHECK: float: f8E3M4
+        print("float:", Float8E3M4Type.get())
         # CHECK: float: f8E4M3
         print("float:", Float8E4M3Type.get())
         # CHECK: float: f8E4M3FN
@@ -605,6 +609,7 @@ def testTypeIDs():
         types = [
             (IntegerType, IntegerType.get_signless(16)),
             (IndexType, IndexType.get()),
+            (Float8E3M4Type, Float8E3M4Type.get()),
             (Float8E4M3Type, Float8E4M3Type.get()),
             (Float8E4M3FNType, Float8E4M3FNType.get()),
             (Float8E5M2Type, Float8E5M2Type.get()),
@@ -629,6 +634,7 @@ def testTypeIDs():
 
         # CHECK: IntegerType(i16)
         # CHECK: IndexType(index)
+        # CHECK: Float8E3M4Type(f8E3M4)
         # CHECK: Float8E4M3Type(f8E4M3)
         # CHECK: Float8E4M3FNType(f8E4M3FN)
         # CHECK: Float8E5M2Type(f8E5M2)
@@ -707,6 +713,9 @@ def testConcreteTypesRoundTrip():
         # CHECK: F64Type
         # CHECK: F64Type(f64)
         print_downcasted(F64Type.get())
+        # CHECK: Float8E3M4Type
+        # CHECK: Float8E3M4Type(f8E3M4)
+        print_downcasted(Float8E3M4Type.get())
         # CHECK: Float8E4M3B11FNUZType
         # CHECK: Float8E4M3B11FNUZType(f8E4M3B11FNUZ)
         print_downcasted(Float8E4M3B11FNUZType.get())

mlir/utils/lldb-scripts/mlirDataFormatters.py

@@ -56,6 +56,7 @@ builtin_attr_type_mnemonics = {
     "mlir::Float8E5M2FNUZType": '"f8E5M2FNUZ"',
     "mlir::Float8E4M3FNUZType": '"f8E4M3FNUZ"',
     "mlir::Float8E4M3B11FNUZType": '"f8E4M3B11FNUZ"',
+    "mlir::Float8E3M4Type": '"f8E3M4"',
     "mlir::BFloat16Type": '"bf16"',
     "mlir::Float16Type": '"f16"',
     "mlir::FloatTF32Type": '"tf32"',

mlir/utils/tree-sitter-mlir/grammar.js

@@ -230,8 +230,8 @@ const common = {
   integer_type : $ =>
       token(seq(choice('si', 'ui', 'i'), /[1-9]/, repeat(/[0-9]/))),
   float_type : $ => token(
-      choice('f16', 'f32', 'f64', 'f80', 'f128', 'bf16', 'f8E4M3FN', 'f8E4M3',
-             'f8E5M2')),
+      choice('f16', 'f32', 'f64', 'f80', 'f128', 'bf16', 'f8E3M4', 'f8E4M3FN',
+             'f8E4M3', 'f8E5M2')),
   index_type : $ => token('index'),
   none_type : $ => token('none'),
   complex_type : $ => seq(token('complex'), '<', $._prim_type, '>'),