Fix issue of missing sign in binary_float_op when result of rem is zero

compiler/rustc_apfloat/src/ieee.rs

@@ -1001,6 +1001,7 @@ impl<S: Semantics> Float for IeeeFloat<S> {
             (Category::Infinity, _) | (_, Category::Zero) => Status::INVALID_OP.and(Self::NAN),
 
             (Category::Normal, Category::Normal) => {
+                let sign = self.sign;
                 while self.is_finite_non_zero()
                     && rhs.is_finite_non_zero()
                     && self.cmp_abs_normal(rhs) != Ordering::Less
@@ -1015,6 +1016,10 @@ impl<S: Semantics> Float for IeeeFloat<S> {
                     self = unpack!(status=, self - v);
                     assert_eq!(status, Status::OK);
                 }
+                // IEEE754 requires this
+                if self.is_zero() {
+                    self.sign = sign;
+                }
                 Status::OK.and(self)
             }
         }

tests/ui/numbers-arithmetic/issue-109567.rs

@@ -0,0 +1,14 @@
+// run-pass
+// check-run-results
+
+fn f() -> f64 {
+    std::hint::black_box(-1.0) % std::hint::black_box(-1.0)
+}
+
+const G: f64 = -1.0 % -1.0;
+
+pub fn main() {
+    assert_eq!(-1, G.signum() as i32);
+    assert_eq!((-0.0_f64).to_bits(), G.to_bits());
+    assert_eq!(f().signum(), G.signum());
+}