Advance the port to llvm/llvm-project@2b6b8cb

(last APFloat-related LLVM commit from 2019).

Author: eddyb

Cargo.toml

@@ -2,7 +2,7 @@
 members = ["fuzz"]
 
 [workspace.package]
-version = "0.0.2+llvm-69f6098e8931"
+version = "0.0.3+llvm-2b6b8cb10c87"
 edition = "2021"
 license = "Apache-2.0 WITH LLVM-exception"
 

src/ieee.rs

@@ -1866,17 +1866,18 @@ impl<S: Semantics> IeeeFloat<S> {
                     chars.next();
                 }
 
-                any_digits = false;
+                let mut any_exp_digits = false;
                 for c in chars {
                     if let Some(value) = c.to_digit(10) {
-                        any_digits = true;
+                        any_exp_digits = true;
                         dec_exp = dec_exp.saturating_mul(10).saturating_add(value as i32);
                     } else {
                         return Err(ParseError("Invalid character in exponent"));
                     }
                 }
-                if !any_digits {
-                    return Err(ParseError("Exponent has no digits"));
+                // Treat no exponent as 0 to match binutils
+                if !any_exp_digits {
+                    assert_eq!(dec_exp, 0);
                 }
 
                 if exp_minus {
@@ -2512,23 +2513,22 @@ mod sig {
         // an addition or subtraction.
         // Subtraction is more subtle than one might naively expect.
         if *a_sign ^ b_sign {
-            let (reverse, loss);
+            let loss;
 
             if bits == 0 {
-                reverse = cmp(a_sig, b_sig) == Ordering::Less;
                 loss = Loss::ExactlyZero;
             } else if bits > 0 {
                 loss = shift_right(b_sig, &mut 0, (bits - 1) as usize);
                 shift_left(a_sig, a_exp, 1);
-                reverse = false;
             } else {
                 loss = shift_right(a_sig, a_exp, (-bits - 1) as usize);
                 shift_left(b_sig, &mut 0, 1);
-                reverse = true;
             }
 
             let borrow = (loss != Loss::ExactlyZero) as Limb;
-            if reverse {
+
+            // Should we reverse the subtraction.
+            if cmp(a_sig, b_sig) == Ordering::Less {
                 // The code above is intended to ensure that no borrow is necessary.
                 assert_eq!(sub(b_sig, a_sig, borrow), 0);
                 a_sig.copy_from_slice(b_sig);

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/69f6098e89312b934ed87e4cd3603401a9b436b4
+//! https://github.com/llvm/llvm-project/commit/2b6b8cb10c870d64f7cc29d21fc27cef3c7e0056
 //! * `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
@@ -48,6 +48,11 @@ bitflags! {
     /// IEEE-754R 7: Default exception handling.
     ///
     /// UNDERFLOW or OVERFLOW are always returned or-ed with INEXACT.
+    ///
+    /// APFloat models this behavior specified by IEEE-754:
+    ///   "For operations producing results in floating-point format, the default
+    ///    result of an operation that signals the invalid operation exception
+    ///    shall be a quiet NaN."
     #[must_use]
     pub struct Status: u8 {
         const OK = 0x00;
@@ -132,7 +137,7 @@ impl Neg for Round {
 }
 
 /// A signed type to represent a floating point number's unbiased exponent.
-pub type ExpInt = i16;
+pub type ExpInt = i32;
 
 // \c ilogb error results.
 pub const IEK_INF: ExpInt = ExpInt::max_value();