[Clang][BFloat16] Upgrade __bf16 by supporting increment/decrement op…

…erations

Since __bf16 has been upgraded from a storage-only type to an arithmetic type in https://reviews.llvm.org/rGe62175736551abf40a3410bc246f58e650eb8158, it should support all the basic arithmetic operations like other float types, including increment and decrement.

Reviewed By: pengfei

Differential Revision: https://reviews.llvm.org/D152768

clang/lib/CodeGen/CGExprScalar.cpp

@@ -2764,8 +2764,8 @@ ScalarExprEmitter::EmitScalarPrePostIncDec(const UnaryOperator *E, LValue LV,
       amt = llvm::ConstantFP::get(VMContext,
                                   llvm::APFloat(static_cast<double>(amount)));
     else {
-      // Remaining types are Half, LongDouble, __ibm128 or __float128. Convert
-      // from float.
+      // Remaining types are Half, Bfloat16, LongDouble, __ibm128 or __float128. 
+      // Convert from float.
       llvm::APFloat F(static_cast<float>(amount));
       bool ignored;
       const llvm::fltSemantics *FS;
@@ -2775,6 +2775,8 @@ ScalarExprEmitter::EmitScalarPrePostIncDec(const UnaryOperator *E, LValue LV,
         FS = &CGF.getTarget().getFloat128Format();
       else if (value->getType()->isHalfTy())
         FS = &CGF.getTarget().getHalfFormat();
+      else if (value->getType()->isBFloatTy())
+        FS = &CGF.getTarget().getBFloat16Format();
       else if (value->getType()->isPPC_FP128Ty())
         FS = &CGF.getTarget().getIbm128Format();
       else

clang/test/Sema/arm-bfloat.cpp

@@ -19,6 +19,8 @@ void test(bool b) {
   bf16 - bf16;
   bf16 * bf16;
   bf16 / bf16;
+  ++bf16;
+  --bf16;
 
   __fp16 fp16;