Add IeeeFloat::is_representable_as_normal_in

Upstream LLVM commit: 69668590592fcca2c2b22ba2257be57f0319fc9c

The following commits are skipped:
* 9395cf063a013003704118deccf7633533170a5b: reverted by next commit
* 69668590592fcca2c2b22ba2257be57f0319fc9c: reverts previous commit

Author: eduardosm

Cargo.toml

@@ -2,7 +2,7 @@
 members = ["fuzz"]
 
 [workspace.package]
-version = "0.2.1+llvm-3d11652bbee4"
+version = "0.2.1+llvm-69668590592f"
 edition = "2021"
 license = "Apache-2.0 WITH LLVM-exception"
 

src/ieee.rs

@@ -576,6 +576,24 @@ impl<S: Semantics> Neg for IeeeFloat<S> {
     }
 }
 
+impl<Src: Semantics> IeeeFloat<Src> {
+    /// Returns true if any number described by `Self` can be precisely represented
+    /// by a normal (not subnormal) value in `IeeeFloat<Dst>`.
+    pub const fn is_representable_as_normal_in<Dst: Semantics>() -> bool {
+        // Exponent range must be larger.
+        if Src::MAX_EXP >= Dst::MAX_EXP || Src::MIN_EXP <= Dst::MIN_EXP {
+            return false;
+        }
+
+        // If the mantissa is long enough, the result value could still be denormal
+        // with a larger exponent range.
+        //
+        // FIXME: This condition is probably not accurate but also shouldn't be a
+        // practical concern with existing types.
+        return Dst::PRECISION >= Src::PRECISION;
+    }
+}
+
 /// Prints this value as a decimal string.
 ///
 /// \param precision The maximum number of digits of

src/lib.rs

@@ -1,6 +1,6 @@
 //! Port of LLVM's APFloat software floating-point implementation from the
 //! following C++ sources (please update commit hash when backporting):
-//! <https://github.com/llvm/llvm-project/commit/3d11652bbee4cd6782c474e28cb2ab58fc93f245>
+//! <https://github.com/llvm/llvm-project/commit/69668590592fcca2c2b22ba2257be57f0319fc9c>
 //! * `llvm/include/llvm/ADT/APFloat.h` -> `Float` and `FloatConvert` traits
 //! * `llvm/lib/Support/APFloat.cpp` -> `ieee` and `ppc` modules
 //! * `llvm/unittests/ADT/APFloatTest.cpp` -> `tests` directory