cleanup: Reuse MinInt and Int from libm in compiler-builtins

Since the two crates are now in the same repo, it is easier to share
code. Begin some deduplication with the integer traits.

Author: tgross35

builtins-test/src/lib.rs

@@ -40,6 +40,75 @@ pub const N: u32 = if cfg!(target_arch = "x86_64") && !cfg!(debug_assertions) {
     10_000
 };
 
+/// Additional constants that determine how the integer gets fuzzed.
+trait FuzzInt: MinInt {
+    /// LUT used for maximizing the space covered and minimizing the computational cost of fuzzing
+    /// in `builtins-test`. For example, Self = u128 produces [0,1,2,7,8,15,16,31,32,63,64,95,96,
+    /// 111,112,119,120,125,126,127].
+    const FUZZ_LENGTHS: [u8; 20] = make_fuzz_lengths(Self::BITS);
+
+    /// The number of entries of `FUZZ_LENGTHS` actually used. The maximum is 20 for u128.
+    const FUZZ_NUM: usize = {
+        let log2 = Self::BITS.ilog2() as usize;
+        if log2 == 3 {
+            // case for u8
+            6
+        } else {
+            // 3 entries on each extreme, 2 in the middle, and 4 for each scale of intermediate
+            // boundaries.
+            8 + (4 * (log2 - 4))
+        }
+    };
+}
+
+impl<I> FuzzInt for I where I: MinInt {}
+
+const fn make_fuzz_lengths(bits: u32) -> [u8; 20] {
+    let mut v = [0u8; 20];
+    v[0] = 0;
+    v[1] = 1;
+    v[2] = 2; // important for parity and the iX::MIN case when reversed
+    let mut i = 3;
+
+    // No need for any more until the byte boundary, because there should be no algorithms
+    // that are sensitive to anything not next to byte boundaries after 2. We also scale
+    // in powers of two, which is important to prevent u128 corner tests from getting too
+    // big.
+    let mut l = 8;
+    loop {
+        if l >= ((bits / 2) as u8) {
+            break;
+        }
+        // get both sides of the byte boundary
+        v[i] = l - 1;
+        i += 1;
+        v[i] = l;
+        i += 1;
+        l *= 2;
+    }
+
+    if bits != 8 {
+        // add the lower side of the middle boundary
+        v[i] = ((bits / 2) - 1) as u8;
+        i += 1;
+    }
+
+    // We do not want to jump directly from the Self::BITS/2 boundary to the Self::BITS
+    // boundary because of algorithms that split the high part up. We reverse the scaling
+    // as we go to Self::BITS.
+    let mid = i;
+    let mut j = 1;
+    loop {
+        v[i] = (bits as u8) - (v[mid - j]) - 1;
+        if j == mid {
+            break;
+        }
+        i += 1;
+        j += 1;
+    }
+    v
+}
+
 /// Random fuzzing step. When run several times, it results in excellent fuzzing entropy such as:
 /// 11110101010101011110111110011111
 /// 10110101010100001011101011001010
@@ -92,10 +161,9 @@ fn fuzz_step<I: Int>(rng: &mut Xoshiro128StarStar, x: &mut I) {
 macro_rules! edge_cases {
     ($I:ident, $case:ident, $inner:block) => {
         for i0 in 0..$I::FUZZ_NUM {
-            let mask_lo = (!$I::UnsignedInt::ZERO).wrapping_shr($I::FUZZ_LENGTHS[i0] as u32);
+            let mask_lo = (!$I::Unsigned::ZERO).wrapping_shr($I::FUZZ_LENGTHS[i0] as u32);
             for i1 in i0..I::FUZZ_NUM {
-                let mask_hi =
-                    (!$I::UnsignedInt::ZERO).wrapping_shl($I::FUZZ_LENGTHS[i1 - i0] as u32);
+                let mask_hi = (!$I::Unsigned::ZERO).wrapping_shl($I::FUZZ_LENGTHS[i1 - i0] as u32);
                 let $case = I::from_unsigned(mask_lo & mask_hi);
                 $inner
             }
@@ -107,7 +175,7 @@ macro_rules! edge_cases {
 /// edge cases, followed by a more random fuzzer that runs `n` times.
 pub fn fuzz<I: Int, F: FnMut(I)>(n: u32, mut f: F)
 where
-    <I as MinInt>::UnsignedInt: Int,
+    <I as MinInt>::Unsigned: Int,
 {
     // edge case tester. Calls `f` 210 times for u128.
     // zero gets skipped by the loop
@@ -128,7 +196,7 @@ where
 /// The same as `fuzz`, except `f` has two inputs.
 pub fn fuzz_2<I: Int, F: Fn(I, I)>(n: u32, f: F)
 where
-    <I as MinInt>::UnsignedInt: Int,
+    <I as MinInt>::Unsigned: Int,
 {
     // Check cases where the first and second inputs are zero. Both call `f` 210 times for `u128`.
     edge_cases!(I, case, {

compiler-builtins/src/float/add.rs

@@ -1,5 +1,5 @@
 use crate::float::Float;
-use crate::int::{CastInto, Int, MinInt};
+use crate::int::{CastFrom, CastInto, Int, MinInt};
 
 /// Returns `a + b`
 fn add<F: Float>(a: F, b: F) -> F
@@ -12,7 +12,7 @@ where
     let one = F::Int::ONE;
     let zero = F::Int::ZERO;
 
-    let bits = F::BITS.cast();
+    let bits: F::Int = F::BITS.cast();
     let significand_bits = F::SIG_BITS;
     let max_exponent = F::EXP_SAT;
 
@@ -115,9 +115,10 @@ where
     let align = a_exponent.wrapping_sub(b_exponent).cast();
     if align != MinInt::ZERO {
         if align < bits {
-            let sticky =
-                F::Int::from_bool(b_significand << bits.wrapping_sub(align).cast() != MinInt::ZERO);
-            b_significand = (b_significand >> align.cast()) | sticky;
+            let sticky = F::Int::from_bool(
+                b_significand << u32::cast_from(bits.wrapping_sub(align)) != MinInt::ZERO,
+            );
+            b_significand = (b_significand >> u32::cast_from(align)) | sticky;
         } else {
             b_significand = one; // sticky; b is known to be non-zero.
         }
@@ -132,8 +133,8 @@ where
         // If partial cancellation occured, we need to left-shift the result
         // and adjust the exponent:
         if a_significand < implicit_bit << 3 {
-            let shift =
-                a_significand.leading_zeros() as i32 - (implicit_bit << 3).leading_zeros() as i32;
+            let shift = a_significand.leading_zeros() as i32
+                - (implicit_bit << 3u32).leading_zeros() as i32;
             a_significand <<= shift;
             a_exponent -= shift;
         }
@@ -159,9 +160,10 @@ where
         // Result is denormal before rounding; the exponent is zero and we
         // need to shift the significand.
         let shift = (1 - a_exponent).cast();
-        let sticky =
-            F::Int::from_bool((a_significand << bits.wrapping_sub(shift).cast()) != MinInt::ZERO);
-        a_significand = (a_significand >> shift.cast()) | sticky;
+        let sticky = F::Int::from_bool(
+            (a_significand << u32::cast_from(bits.wrapping_sub(shift))) != MinInt::ZERO,
+        );
+        a_significand = (a_significand >> u32::cast_from(shift)) | sticky;
         a_exponent = 0;
     }
 

compiler-builtins/src/float/conv.rs

@@ -72,7 +72,7 @@ mod int_to_float {
         F: Float,
         I: Int,
         F::Int: CastFrom<I>,
-        Conv: Fn(I::UnsignedInt) -> F::Int,
+        Conv: Fn(I::Unsigned) -> F::Int,
     {
         let sign_bit = F::Int::cast_from(i >> (I::BITS - 1)) << (F::BITS - 1);
         F::from_bits(conv(i.unsigned_abs()) | sign_bit)
@@ -313,10 +313,10 @@ intrinsics! {
 fn float_to_unsigned_int<F, U>(f: F) -> U
 where
     F: Float,
-    U: Int<UnsignedInt = U>,
+    U: Int<Unsigned = U>,
     F::Int: CastInto<U>,
     F::Int: CastFrom<u32>,
-    F::Int: CastInto<U::UnsignedInt>,
+    F::Int: CastInto<U::Unsigned>,
     u32: CastFrom<F::Int>,
 {
     float_to_int_inner::<F, U, _, _>(f.to_bits(), |i: U| i, || U::MAX)
@@ -327,8 +327,8 @@ fn float_to_signed_int<F, I>(f: F) -> I
 where
     F: Float,
     I: Int + Neg<Output = I>,
-    I::UnsignedInt: Int,
-    F::Int: CastInto<I::UnsignedInt>,
+    I::Unsigned: Int,
+    F::Int: CastInto<I::Unsigned>,
     F::Int: CastFrom<u32>,
     u32: CastFrom<F::Int>,
 {
@@ -355,27 +355,27 @@ where
     I: Int,
     FnFoo: FnOnce(I) -> I,
     FnOob: FnOnce() -> I,
-    I::UnsignedInt: Int,
-    F::Int: CastInto<I::UnsignedInt>,
+    I::Unsigned: Int,
+    F::Int: CastInto<I::Unsigned>,
     F::Int: CastFrom<u32>,
     u32: CastFrom<F::Int>,
 {
     let int_max_exp = F::EXP_BIAS + I::MAX.ilog2() + 1;
-    let foobar = F::EXP_BIAS + I::UnsignedInt::BITS - 1;
+    let foobar = F::EXP_BIAS + I::Unsigned::BITS - 1;
 
     if fbits < F::ONE.to_bits() {
         // < 0 gets rounded to 0
         I::ZERO
     } else if fbits < F::Int::cast_from(int_max_exp) << F::SIG_BITS {
         // >= 1, < integer max
-        let m_base = if I::UnsignedInt::BITS >= F::Int::BITS {
-            I::UnsignedInt::cast_from(fbits) << (I::BITS - F::SIG_BITS - 1)
+        let m_base = if I::Unsigned::BITS >= F::Int::BITS {
+            I::Unsigned::cast_from(fbits) << (I::BITS - F::SIG_BITS - 1)
         } else {
-            I::UnsignedInt::cast_from(fbits >> (F::SIG_BITS - I::BITS + 1))
+            I::Unsigned::cast_from(fbits >> (F::SIG_BITS - I::BITS + 1))
         };
 
         // Set the implicit 1-bit.
-        let m: I::UnsignedInt = (I::UnsignedInt::ONE << (I::BITS - 1)) | m_base;
+        let m: I::Unsigned = (I::Unsigned::ONE << (I::BITS - 1)) | m_base;
 
         // Shift based on the exponent and bias.
         let s: u32 = (foobar) - u32::cast_from(fbits >> F::SIG_BITS);

compiler-builtins/src/float/div.rs

@@ -370,7 +370,7 @@ where
         let hi_corr: F::Int = corr_uq1 >> hw;
 
         // x_UQ0 * corr_UQ1 = (x_UQ0_hw * 2^HW) * (hi_corr * 2^HW + lo_corr) - corr_UQ1
-        let mut x_uq0: F::Int = ((F::Int::from(x_uq0_hw) * hi_corr) << 1)
+        let mut x_uq0: F::Int = ((F::Int::from(x_uq0_hw) * hi_corr) << 1u32)
             .wrapping_add((F::Int::from(x_uq0_hw) * lo_corr) >> (hw - 1))
             // 1 to account for the highest bit of corr_UQ1 can be 1
             // 1 to account for possible carry

compiler-builtins/src/float/mul.rs

@@ -143,7 +143,7 @@ where
         // a zero of the appropriate sign.  Mathematically there is no need to
         // handle this case separately, but we make it a special case to
         // simplify the shift logic.
-        let shift = one.wrapping_sub(product_exponent.cast()).cast();
+        let shift: u32 = one.wrapping_sub(product_exponent.cast()).cast();
         if shift >= bits {
             return F::from_bits(product_sign);
         }

compiler-builtins/src/float/traits.rs

@@ -20,10 +20,10 @@ pub trait Float:
     + ops::Rem<Output = Self>
 {
     /// A uint of the same width as the float
-    type Int: Int<OtherSign = Self::SignedInt, UnsignedInt = Self::Int>;
+    type Int: Int<OtherSign = Self::SignedInt, Unsigned = Self::Int>;
 
     /// A int of the same width as the float
-    type SignedInt: Int + MinInt<OtherSign = Self::Int, UnsignedInt = Self::Int>;
+    type SignedInt: Int + MinInt<OtherSign = Self::Int, Unsigned = Self::Int>;
 
     /// An int capable of containing the exponent bits plus a sign bit. This is signed.
     type ExpInt: Int;

compiler-builtins/src/int/addsub.rs

@@ -22,7 +22,7 @@ impl UAddSub for u128 {}
 
 trait AddSub: Int
 where
-    <Self as MinInt>::UnsignedInt: UAddSub,
+    <Self as MinInt>::Unsigned: UAddSub,
 {
     fn add(self, other: Self) -> Self {
         Self::from_unsigned(self.unsigned().uadd(other.unsigned()))
@@ -37,7 +37,7 @@ impl AddSub for i128 {}
 
 trait Addo: AddSub
 where
-    <Self as MinInt>::UnsignedInt: UAddSub,
+    <Self as MinInt>::Unsigned: UAddSub,
 {
     fn addo(self, other: Self) -> (Self, bool) {
         let sum = AddSub::add(self, other);
@@ -50,7 +50,7 @@ impl Addo for u128 {}
 
 trait Subo: AddSub
 where
-    <Self as MinInt>::UnsignedInt: UAddSub,
+    <Self as MinInt>::Unsigned: UAddSub,
 {
     fn subo(self, other: Self) -> (Self, bool) {
         let sum = AddSub::sub(self, other);

compiler-builtins/src/int/big.rs

@@ -45,7 +45,7 @@ impl i256 {
 impl MinInt for u256 {
     type OtherSign = i256;
 
-    type UnsignedInt = u256;
+    type Unsigned = u256;
 
     const SIGNED: bool = false;
     const BITS: u32 = 256;
@@ -58,7 +58,7 @@ impl MinInt for u256 {
 impl MinInt for i256 {
     type OtherSign = u256;
 
-    type UnsignedInt = u256;
+    type Unsigned = u256;
 
     const SIGNED: bool = false;
     const BITS: u32 = 256;