float: Add tests for f16 conversions to and from decimal

Extend the existing tests for `f32` and `f64` with versions that include
`f16`'s new printing and parsing implementations.

Co-authored-by: Speedy_Lex <[email protected]>

Author: tgross35

library/coretests/Cargo.toml

@@ -26,3 +26,12 @@ test = true
 [dev-dependencies]
 rand = { version = "0.9.0", default-features = false }
 rand_xorshift = { version = "0.4.0", default-features = false }
+
+[lints.rust.unexpected_cfgs]
+level = "warn"
+check-cfg = [
+    'cfg(bootstrap)',
+    # Internal features aren't marked known config by default, we use these to
+    # gate tests.
+    'cfg(target_has_reliable_f16)',
+]

library/coretests/tests/lib.rs

@@ -12,6 +12,7 @@
 #![feature(async_iterator)]
 #![feature(bigint_helper_methods)]
 #![feature(bstr)]
+#![feature(cfg_target_has_reliable_f16_f128)]
 #![feature(char_max_len)]
 #![feature(clone_to_uninit)]
 #![feature(const_eval_select)]
@@ -29,6 +30,7 @@
 #![feature(exact_size_is_empty)]
 #![feature(extend_one)]
 #![feature(extern_types)]
+#![feature(f16)]
 #![feature(float_minimum_maximum)]
 #![feature(flt2dec)]
 #![feature(fmt_internals)]

library/coretests/tests/num/dec2flt/decimal.rs

@@ -7,6 +7,20 @@ const FPATHS_F32: &[FPath<f32>] =
 const FPATHS_F64: &[FPath<f64>] =
     &[((0, 0, false, false), Some(0.0)), ((0, 0, false, false), Some(0.0))];
 
+// FIXME(f16_f128): enable on all targets once possible.
+#[test]
+#[cfg(target_has_reliable_f16)]
+fn check_fast_path_f16() {
+    const FPATHS_F16: &[FPath<f16>] =
+        &[((0, 0, false, false), Some(0.0)), ((0, 0, false, false), Some(0.0))];
+    for ((exponent, mantissa, negative, many_digits), expected) in FPATHS_F16.iter().copied() {
+        let dec = Decimal { exponent, mantissa, negative, many_digits };
+        let actual = dec.try_fast_path::<f16>();
+
+        assert_eq!(actual, expected);
+    }
+}
+
 #[test]
 fn check_fast_path_f32() {
     for ((exponent, mantissa, negative, many_digits), expected) in FPATHS_F32.iter().copied() {

library/coretests/tests/num/dec2flt/float.rs

@@ -1,5 +1,23 @@
 use core::num::dec2flt::float::RawFloat;
 
+// FIXME(f16_f128): enable on all targets once possible.
+#[test]
+#[cfg(target_has_reliable_f16)]
+fn test_f16_integer_decode() {
+    assert_eq!(3.14159265359f16.integer_decode(), (1608, -9, 1));
+    assert_eq!((-8573.5918555f16).integer_decode(), (1072, 3, -1));
+    assert_eq!(2f16.powf(14.0).integer_decode(), (1 << 10, 4, 1));
+    assert_eq!(0f16.integer_decode(), (0, -25, 1));
+    assert_eq!((-0f16).integer_decode(), (0, -25, -1));
+    assert_eq!(f16::INFINITY.integer_decode(), (1 << 10, 6, 1));
+    assert_eq!(f16::NEG_INFINITY.integer_decode(), (1 << 10, 6, -1));
+
+    // Ignore the "sign" (quiet / signalling flag) of NAN.
+    // It can vary between runtime operations and LLVM folding.
+    let (nan_m, nan_p, _nan_s) = f16::NAN.integer_decode();
+    assert_eq!((nan_m, nan_p), (1536, 6));
+}
+
 #[test]
 fn test_f32_integer_decode() {
     assert_eq!(3.14159265359f32.integer_decode(), (13176795, -22, 1));
@@ -34,6 +52,27 @@ fn test_f64_integer_decode() {
 
 /* Sanity checks of computed magic numbers */
 
+// FIXME(f16_f128): enable on all targets once possible.
+#[test]
+#[cfg(target_has_reliable_f16)]
+fn test_f16_consts() {
+    assert_eq!(<f16 as RawFloat>::INFINITY, f16::INFINITY);
+    assert_eq!(<f16 as RawFloat>::NEG_INFINITY, -f16::INFINITY);
+    assert_eq!(<f16 as RawFloat>::NAN.to_bits(), f16::NAN.to_bits());
+    assert_eq!(<f16 as RawFloat>::NEG_NAN.to_bits(), (-f16::NAN).to_bits());
+    assert_eq!(<f16 as RawFloat>::SIG_BITS, 10);
+    assert_eq!(<f16 as RawFloat>::MIN_EXPONENT_ROUND_TO_EVEN, -22);
+    assert_eq!(<f16 as RawFloat>::MAX_EXPONENT_ROUND_TO_EVEN, 5);
+    assert_eq!(<f16 as RawFloat>::MIN_EXPONENT_FAST_PATH, -4);
+    assert_eq!(<f16 as RawFloat>::MAX_EXPONENT_FAST_PATH, 4);
+    assert_eq!(<f16 as RawFloat>::MAX_EXPONENT_DISGUISED_FAST_PATH, 7);
+    assert_eq!(<f16 as RawFloat>::EXP_MIN, -14);
+    assert_eq!(<f16 as RawFloat>::EXP_SAT, 0x1f);
+    assert_eq!(<f16 as RawFloat>::SMALLEST_POWER_OF_TEN, -27);
+    assert_eq!(<f16 as RawFloat>::LARGEST_POWER_OF_TEN, 4);
+    assert_eq!(<f16 as RawFloat>::MAX_MANTISSA_FAST_PATH, 2048);
+}
+
 #[test]
 fn test_f32_consts() {
     assert_eq!(<f32 as RawFloat>::INFINITY, f32::INFINITY);

library/coretests/tests/num/dec2flt/lemire.rs

@@ -1,6 +1,12 @@
 use core::num::dec2flt::float::RawFloat;
 use core::num::dec2flt::lemire::compute_float;
 
+#[cfg(target_has_reliable_f16)]
+fn compute_float16(q: i64, w: u64) -> (i32, u64) {
+    let fp = compute_float::<f16>(q, w);
+    (fp.p_biased, fp.m)
+}
+
 fn compute_float32(q: i64, w: u64) -> (i32, u64) {
     let fp = compute_float::<f32>(q, w);
     (fp.p_biased, fp.m)
@@ -11,23 +17,73 @@ fn compute_float64(q: i64, w: u64) -> (i32, u64) {
     (fp.p_biased, fp.m)
 }
 
+// FIXME(f16_f128): enable on all targets once possible.
+#[test]
+#[cfg(target_has_reliable_f16)]
+fn compute_float_f16_rounding() {
+    // The maximum integer that cna be converted to a `f16` without lost precision.
+    let val = 1 << 11;
+    let scale = 10_u64.pow(10);
+
+    // These test near-halfway cases for half-precision floats.
+    assert_eq!(compute_float16(0, val), (26, 0));
+    assert_eq!(compute_float16(0, val + 1), (26, 0));
+    assert_eq!(compute_float16(0, val + 2), (26, 1));
+    assert_eq!(compute_float16(0, val + 3), (26, 2));
+    assert_eq!(compute_float16(0, val + 4), (26, 2));
+
+    // For the next power up, the two nearest representable numbers are twice as far apart.
+    let val2 = 1 << 12;
+    assert_eq!(compute_float16(0, val2), (27, 0));
+    assert_eq!(compute_float16(0, val2 + 2), (27, 0));
+    assert_eq!(compute_float16(0, val2 + 4), (27, 1));
+    assert_eq!(compute_float16(0, val2 + 6), (27, 2));
+    assert_eq!(compute_float16(0, val2 + 8), (27, 2));
+
+    // These are examples of the above tests, with digits from the exponent shifted
+    // to the mantissa.
+    assert_eq!(compute_float16(-10, val * scale), (26, 0));
+    assert_eq!(compute_float16(-10, (val + 1) * scale), (26, 0));
+    assert_eq!(compute_float16(-10, (val + 2) * scale), (26, 1));
+    // Let's check the lines to see if anything is different in table...
+    assert_eq!(compute_float16(-10, (val + 3) * scale), (26, 2));
+    assert_eq!(compute_float16(-10, (val + 4) * scale), (26, 2));
+
+    // Check the rounding point between infinity and the next representable number down
+    assert_eq!(compute_float16(4, 6), (f16::INFINITE_POWER - 1, 851));
+    assert_eq!(compute_float16(4, 7), (f16::INFINITE_POWER, 0)); // infinity
+    assert_eq!(compute_float16(2, 655), (f16::INFINITE_POWER - 1, 1023));
+}
+
 #[test]
 fn compute_float_f32_rounding() {
+    // the maximum integer that cna be converted to a `f32` without lost precision.
+    let val = 1 << 24;
+    let scale = 10_u64.pow(10);
+
     // These test near-halfway cases for single-precision floats.
-    assert_eq!(compute_float32(0, 16777216), (151, 0));
-    assert_eq!(compute_float32(0, 16777217), (151, 0));
-    assert_eq!(compute_float32(0, 16777218), (151, 1));
-    assert_eq!(compute_float32(0, 16777219), (151, 2));
-    assert_eq!(compute_float32(0, 16777220), (151, 2));
-
-    // These are examples of the above tests, with
-    // digits from the exponent shifted to the mantissa.
-    assert_eq!(compute_float32(-10, 167772160000000000), (151, 0));
-    assert_eq!(compute_float32(-10, 167772170000000000), (151, 0));
-    assert_eq!(compute_float32(-10, 167772180000000000), (151, 1));
+    assert_eq!(compute_float32(0, val), (151, 0));
+    assert_eq!(compute_float32(0, val + 1), (151, 0));
+    assert_eq!(compute_float32(0, val + 2), (151, 1));
+    assert_eq!(compute_float32(0, val + 3), (151, 2));
+    assert_eq!(compute_float32(0, val + 4), (151, 2));
+
+    // For the next power up, the two nearest representable numbers are twice as far apart.
+    let val2 = 1 << 25;
+    assert_eq!(compute_float32(0, val2), (152, 0));
+    assert_eq!(compute_float32(0, val2 + 2), (152, 0));
+    assert_eq!(compute_float32(0, val2 + 4), (152, 1));
+    assert_eq!(compute_float32(0, val2 + 6), (152, 2));
+    assert_eq!(compute_float32(0, val2 + 8), (152, 2));
+
+    // These are examples of the above tests, with digits from the exponent shifted
+    // to the mantissa.
+    assert_eq!(compute_float32(-10, val * scale), (151, 0));
+    assert_eq!(compute_float32(-10, (val + 1) * scale), (151, 0));
+    assert_eq!(compute_float32(-10, (val + 2) * scale), (151, 1));
     // Let's check the lines to see if anything is different in table...
-    assert_eq!(compute_float32(-10, 167772190000000000), (151, 2));
-    assert_eq!(compute_float32(-10, 167772200000000000), (151, 2));
+    assert_eq!(compute_float32(-10, (val + 3) * scale), (151, 2));
+    assert_eq!(compute_float32(-10, (val + 4) * scale), (151, 2));
 
     // Check the rounding point between infinity and the next representable number down
     assert_eq!(compute_float32(38, 3), (f32::INFINITE_POWER - 1, 6402534));
@@ -37,23 +93,38 @@ fn compute_float_f32_rounding() {
 
 #[test]
 fn compute_float_f64_rounding() {
+    // The maximum integer that cna be converted to a `f64` without lost precision.
+    let val = 1 << 53;
+    let scale = 1000;
+
     // These test near-halfway cases for double-precision floats.
-    assert_eq!(compute_float64(0, 9007199254740992), (1076, 0));
-    assert_eq!(compute_float64(0, 9007199254740993), (1076, 0));
-    assert_eq!(compute_float64(0, 9007199254740994), (1076, 1));
-    assert_eq!(compute_float64(0, 9007199254740995), (1076, 2));
-    assert_eq!(compute_float64(0, 9007199254740996), (1076, 2));
-    assert_eq!(compute_float64(0, 18014398509481984), (1077, 0));
-    assert_eq!(compute_float64(0, 18014398509481986), (1077, 0));
-    assert_eq!(compute_float64(0, 18014398509481988), (1077, 1));
-    assert_eq!(compute_float64(0, 18014398509481990), (1077, 2));
-    assert_eq!(compute_float64(0, 18014398509481992), (1077, 2));
-
-    // These are examples of the above tests, with
-    // digits from the exponent shifted to the mantissa.
-    assert_eq!(compute_float64(-3, 9007199254740992000), (1076, 0));
-    assert_eq!(compute_float64(-3, 9007199254740993000), (1076, 0));
-    assert_eq!(compute_float64(-3, 9007199254740994000), (1076, 1));
-    assert_eq!(compute_float64(-3, 9007199254740995000), (1076, 2));
-    assert_eq!(compute_float64(-3, 9007199254740996000), (1076, 2));
+    assert_eq!(compute_float64(0, val), (1076, 0));
+    assert_eq!(compute_float64(0, val + 1), (1076, 0));
+    assert_eq!(compute_float64(0, val + 2), (1076, 1));
+    assert_eq!(compute_float64(0, val + 3), (1076, 2));
+    assert_eq!(compute_float64(0, val + 4), (1076, 2));
+
+    // For the next power up, the two nearest representable numbers are twice as far apart.
+    let val2 = 1 << 54;
+    assert_eq!(compute_float64(0, val2), (1077, 0));
+    assert_eq!(compute_float64(0, val2 + 2), (1077, 0));
+    assert_eq!(compute_float64(0, val2 + 4), (1077, 1));
+    assert_eq!(compute_float64(0, val2 + 6), (1077, 2));
+    assert_eq!(compute_float64(0, val2 + 8), (1077, 2));
+
+    // These are examples of the above tests, with digits from the exponent shifted
+    // to the mantissa.
+    assert_eq!(compute_float64(-3, val * scale), (1076, 0));
+    assert_eq!(compute_float64(-3, (val + 1) * scale), (1076, 0));
+    assert_eq!(compute_float64(-3, (val + 2) * scale), (1076, 1));
+    assert_eq!(compute_float64(-3, (val + 3) * scale), (1076, 2));
+    assert_eq!(compute_float64(-3, (val + 4) * scale), (1076, 2));
+
+    // Check the rounding point between infinity and the next representable number down
+    assert_eq!(compute_float64(308, 1), (f64::INFINITE_POWER - 1, 506821272651936));
+    assert_eq!(compute_float64(308, 2), (f64::INFINITE_POWER, 0)); // infinity
+    assert_eq!(
+        compute_float64(292, 17976931348623157),
+        (f64::INFINITE_POWER - 1, 4503599627370495)
+    );
 }

library/coretests/tests/num/dec2flt/mod.rs

@@ -11,15 +11,23 @@ mod parse;
 // Requires a *polymorphic literal*, i.e., one that can serve as f64 as well as f32.
 macro_rules! test_literal {
     ($x: expr) => {{
+        #[cfg(target_has_reliable_f16)]
+        let x16: f16 = $x;
         let x32: f32 = $x;
         let x64: f64 = $x;
         let inputs = &[stringify!($x).into(), format!("{:?}", x64), format!("{:e}", x64)];
+
         for input in inputs {
-            assert_eq!(input.parse(), Ok(x64));
-            assert_eq!(input.parse(), Ok(x32));
+            assert_eq!(input.parse(), Ok(x64), "failed f64 {input}");
+            assert_eq!(input.parse(), Ok(x32), "failed f32 {input}");
+            #[cfg(target_has_reliable_f16)]
+            assert_eq!(input.parse(), Ok(x16), "failed f16 {input}");
+
             let neg_input = format!("-{input}");
-            assert_eq!(neg_input.parse(), Ok(-x64));
-            assert_eq!(neg_input.parse(), Ok(-x32));
+            assert_eq!(neg_input.parse(), Ok(-x64), "failed f64 {neg_input}");
+            assert_eq!(neg_input.parse(), Ok(-x32), "failed f32 {neg_input}");
+            #[cfg(target_has_reliable_f16)]
+            assert_eq!(neg_input.parse(), Ok(-x16), "failed f16 {neg_input}");
         }
     }};
 }
@@ -84,48 +92,87 @@ fn fast_path_correct() {
     test_literal!(1.448997445238699);
 }
 
+// FIXME(f16_f128): remove gates once tests work on all targets
+
 #[test]
 fn lonely_dot() {
+    #[cfg(target_has_reliable_f16)]
+    assert!(".".parse::<f16>().is_err());
     assert!(".".parse::<f32>().is_err());
     assert!(".".parse::<f64>().is_err());
 }
 
 #[test]
 fn exponentiated_dot() {
+    #[cfg(target_has_reliable_f16)]
+    assert!(".e0".parse::<f16>().is_err());
     assert!(".e0".parse::<f32>().is_err());
     assert!(".e0".parse::<f64>().is_err());
 }
 
 #[test]
 fn lonely_sign() {
-    assert!("+".parse::<f32>().is_err());
-    assert!("-".parse::<f64>().is_err());
+    #[cfg(target_has_reliable_f16)]
+    assert!("+".parse::<f16>().is_err());
+    assert!("-".parse::<f32>().is_err());
+    assert!("+".parse::<f64>().is_err());
 }
 
 #[test]
 fn whitespace() {
+    #[cfg(target_has_reliable_f16)]
+    assert!("1.0 ".parse::<f16>().is_err());
     assert!(" 1.0".parse::<f32>().is_err());
     assert!("1.0 ".parse::<f64>().is_err());
 }
 
 #[test]
 fn nan() {
+    #[cfg(target_has_reliable_f16)]
+    {
+        assert!("NaN".parse::<f16>().unwrap().is_nan());
+        assert!("-NaN".parse::<f16>().unwrap().is_nan());
+    }
+
     assert!("NaN".parse::<f32>().unwrap().is_nan());
+    assert!("-NaN".parse::<f32>().unwrap().is_nan());
+
     assert!("NaN".parse::<f64>().unwrap().is_nan());
+    assert!("-NaN".parse::<f64>().unwrap().is_nan());
 }
 
 #[test]
 fn inf() {
-    assert_eq!("inf".parse(), Ok(f64::INFINITY));
-    assert_eq!("-inf".parse(), Ok(f64::NEG_INFINITY));
+    #[cfg(target_has_reliable_f16)]
+    {
+        assert_eq!("inf".parse(), Ok(f16::INFINITY));
+        assert_eq!("-inf".parse(), Ok(f16::NEG_INFINITY));
+    }
+
     assert_eq!("inf".parse(), Ok(f32::INFINITY));
     assert_eq!("-inf".parse(), Ok(f32::NEG_INFINITY));
+
+    assert_eq!("inf".parse(), Ok(f64::INFINITY));
+    assert_eq!("-inf".parse(), Ok(f64::NEG_INFINITY));
 }
 
 #[test]
 fn massive_exponent() {
+    #[cfg(target_has_reliable_f16)]
+    {
+        let max = i16::MAX;
+        assert_eq!(format!("1e{max}000").parse(), Ok(f16::INFINITY));
+        assert_eq!(format!("1e-{max}000").parse(), Ok(0.0f16));
+        assert_eq!(format!("1e{max}000").parse(), Ok(f16::INFINITY));
+    }
+
+    let max = i32::MAX;
+    assert_eq!(format!("1e{max}000").parse(), Ok(f32::INFINITY));
+    assert_eq!(format!("1e-{max}000").parse(), Ok(0.0f32));
+    assert_eq!(format!("1e{max}000").parse(), Ok(f32::INFINITY));
+
     let max = i64::MAX;
     assert_eq!(format!("1e{max}000").parse(), Ok(f64::INFINITY));
-    assert_eq!(format!("1e-{max}000").parse(), Ok(0.0));
+    assert_eq!(format!("1e-{max}000").parse(), Ok(0.0f64));
     assert_eq!(format!("1e{max}000").parse(), Ok(f64::INFINITY));
 }