wip: Generic cbrt

Author: tgross35

etc/consts-cbrt.jl

@@ -0,0 +1,23 @@
+
+using Printf
+using Remez
+
+function main()
+    run_one("f64", "hf64!", 53)
+end
+
+function run_one(name::String, hf::String, precision::Integer)
+    setprecision(precision)
+
+    println("Constants for ", name)
+    
+    println("const ESCALE: [Self; 3] = [")
+    for n in 0:2
+        val = big(2) ^ (n / 3)
+        @printf "    %s(\"%a\"),\n" hf val
+    end
+    print("];")
+
+end
+
+main()

etc/update-api-list.py

@@ -22,6 +22,8 @@
 
 # These files do not trigger a retest.
 IGNORED_SOURCES = ["libm/src/libm_helper.rs", "libm/src/math/support/float_traits.rs"]
+# Same as above, limited to specific functions
+IGNORED_SOURCES_MAP = {"fma": ["libm/src/math/cbrt.rs"]}
 
 IndexTy: TypeAlias = dict[str, dict[str, Any]]
 """Type of the `index` item in rustdoc's JSON output"""
@@ -137,6 +139,8 @@ def _init_defs(self, index: IndexTy) -> None:
 
             for src in IGNORED_SOURCES:
                 sources.discard(src)
+            for src in IGNORED_SOURCES_MAP.get(name, []):
+                sources.discard(src)
 
         # Sort the set
         self.defs = {k: sorted(v) for (k, v) in defs.items()}

libm-test/src/domain.rs

@@ -196,7 +196,7 @@ impl<F: Float, I: Int> EitherPrim<Domain<F>, Domain<I>> {
             Box::new((0..u8::MAX).map(|scale| {
                 let mut base = F::ZERO;
                 for _ in 0..scale {
-                    base = base - F::ONE;
+                    base -= F::ONE;
                 }
                 base
             }))

libm-test/src/f8_impl.rs

@@ -38,6 +38,13 @@ impl Float for f8 {
     const NEG_PI: Self = Self::ZERO;
     const FRAC_PI_2: Self = Self::ZERO;
 
+    /// `2^sig_bits`
+    const TWO_POW_SIG_BITS: Self =
+        Self(((Self::SIG_BITS + Self::EXP_BIAS) as Self::Int) << Self::SIG_BITS);
+    /// `2^-sig_bits`
+    const TWO_POW_NEG_SIG_BITS: Self =
+        Self(((-(Self::SIG_BITS as i32) + Self::EXP_BIAS as i32) as Self::Int) << Self::SIG_BITS);
+
     const BITS: u32 = 8;
     const SIG_BITS: u32 = 3;
     const SIGN_MASK: Self::Int = 0b1_0000_000;