[GitHub] [incubator-tvm] tqchen commented on a change in pull request #5601: [TVM Core] Add bfloat16

[GitBox]

tqchen commented on a change in pull request #5601:
URL: https://github.com/apache/incubator-tvm/pull/5601#discussion_r427706238



##########
File path: include/tvm/runtime/c_runtime_api.h
##########
@@ -114,6 +114,7 @@ typedef enum {
   kTVMNNVMLast = 20U,
   // The following section of code is used for non-reserved types.
   kTVMExtReserveEnd = 64U,
+  kTVMBFloat = 65U,

Review comment:
       We do not want BFloat to be passed as PackedFunc argument, most 
packedfunc argument should always be passed as double

##########
File path: include/tvm/runtime/data_type.h
##########
@@ -297,6 +302,8 @@ inline const char* TypeCode2Str(int type_code) {
       return "Object";
     case kTVMObjectRValueRefArg:
       return "ObjectRValueRefArg";
+    case kTVMBFloat:
+      return "bf";

Review comment:
       bfloat

##########
File path: src/target/llvm/codegen_llvm.cc
##########
@@ -555,12 +558,48 @@ void CodeGenLLVM::CreateSerialFor(llvm::Value* begin, 
llvm::Value* end, llvm::Va
   builder_->SetInsertPoint(for_end);
 }
 
+static llvm::Value* GetInt32VectorOrScalar(
+    llvm::IRBuilder<llvm::ConstantFolder, llvm::IRBuilderDefaultInserter>* 
builder, uint32_t v,
+    int lanes) {
+  if (lanes == 1) {
+    return builder->getInt32(v);
+  } else {
+    std::vector<llvm::Constant*> consts;
+    for (int i = 0; i < lanes; i++) {
+      consts.emplace_back(builder->getInt32(v));
+    }
+    return llvm::ConstantVector::get(consts);
+  }
+}
+
 // cast operatpr
 llvm::Value* CodeGenLLVM::CreateCast(DataType from, DataType to, llvm::Value* 
value) {
   llvm::Type* target = DTypeToLLVMType(to);
   if (value->getType() == target) return value;
   if (to.is_handle()) {
     return builder_->CreateBitCast(value, target);
+  } else if (to.is_float() && from.is_bfloat()) {
+    CHECK_EQ(from.bits(), 16);

Review comment:
       If LLVM does not support bfloat, then perhaps we should do the 
legalization as a TIR=>TIR pass as opposed to do it in LLVM

##########
File path: include/tvm/runtime/data_type.h
##########
@@ -81,6 +82,10 @@ class DataType {
   bool is_float() const { return code() == DataType::kFloat; }
   /*! \return whether type is a float16 type. */
   bool is_float16() const { return is_float() && bits() == 16; }
+  /*! \return whether type is a bfloat type. */
+  bool is_bfloat() const { return code() == DataType::kBFloat; }

Review comment:
       given that only bfloat16 is defined, is_bf16 is a good enough function




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