[MLIR] Use f64 APFloat (#3453)

* Use f64 APFloat

* PR feedback

src/contrib/mlir/lowerer.cpp

@@ -100,6 +100,8 @@ namespace
                                  PatternRewriter& rewriter,
                                  DialectLoweringPass& pass);
 
+    ValueHandle createZeroConstant(mlir::Type type);
+
     /// Conversion from types in the nGraph dialect to the Standard dialect.
     class NGraphTypeConverter : public TypeConverter
     {
@@ -509,20 +511,8 @@ namespace
 
         LoopNestBuilder(pivs, lbs, ubs, steps)([&] {
             ValueHandle val = iLHS(ivs);
-            if (auto floatTy = elemTy.dyn_cast<FloatType>())
-            {
-                ValueHandle zero = intrinsics::constant_float(llvm::APFloat(0.0f), floatTy);
-                iRes(ivs) = intrinsics::select(val > zero, val, zero);
-            }
-            else if (auto intTy = elemTy.dyn_cast<IntegerType>())
-            {
-                ValueHandle zero = intrinsics::constant_int(0, intTy.getWidth());
+            ValueHandle zero = createZeroConstant(elemTy);
             iRes(ivs) = intrinsics::select(val > zero, val, zero);
-            }
-            else
-            {
-                NGRAPH_CHECK(false, "Unsupported type for Relu");
-            }
         });
 
         rewriter.replaceOp(op, {result});
@@ -840,22 +830,10 @@ namespace
             ValueHandle val = iLHS(ivs);
             if (isa<NGNegOp>(op))
             {
-                if (auto floatTy = elemTy.dyn_cast<FloatType>())
-                {
-                    ValueHandle zero = intrinsics::constant_float(llvm::APFloat(0.0f), floatTy);
-                    iRes(ivs) = zero - val;
-                }
-                else if (auto intTy = elemTy.dyn_cast<IntegerType>())
-                {
-                    ValueHandle zero = intrinsics::constant_int(0, intTy.getWidth());
+                ValueHandle zero = createZeroConstant(elemTy);
                 iRes(ivs) = zero - val;
             }
             else
-                {
-                    NGRAPH_CHECK(false, "Unsupported type for Negative");
-                }
-            }
-            else
             {
                 NGRAPH_CHECK(false, "Unsupported op");
             }
@@ -1029,6 +1007,30 @@ namespace
 
         rewriter.replaceOp(op, result);
     }
+
+    ValueHandle createZeroConstant(mlir::Type type)
+    {
+        if (auto floatTy = type.dyn_cast<FloatType>())
+        {
+            if (floatTy.isF32())
+            {
+                return intrinsics::constant_float(llvm::APFloat(0.0f), floatTy);
+            }
+            else if (floatTy.isF64())
+            {
+                return intrinsics::constant_float(llvm::APFloat(0.0), floatTy);
+            }
+            else
+            {
+                NGRAPH_UNREACHABLE("Unsupported floating-point precision");
+            }
+        }
+        else if (auto intTy = type.dyn_cast<IntegerType>())
+        {
+            return intrinsics::constant_int(0, intTy.getWidth());
+        }
+        NGRAPH_UNREACHABLE("Unsupported type");
+    }
 }
 
 namespace mlir