1 files changed, 225 insertions, 0 deletions
diff --git a/vendor/crc32fast/src/specialized/pclmulqdq.rs b/vendor/crc32fast/src/specialized/pclmulqdq.rs
new file mode 100644
index 0000000..84a60ca
--- /dev/null
+++ b/vendor/crc32fast/src/specialized/pclmulqdq.rs
@@ -0,0 +1,225 @@
+#[cfg(target_arch = "x86")]
+use core::arch::x86 as arch;
+#[cfg(target_arch = "x86_64")]
+use core::arch::x86_64 as arch;
+
+#[derive(Clone)]
+pub struct State {
+    state: u32,
+}
+
+impl State {
+    #[cfg(not(feature = "std"))]
+    pub fn new(state: u32) -> Option<Self> {
+        if cfg!(target_feature = "pclmulqdq")
+            && cfg!(target_feature = "sse2")
+            && cfg!(target_feature = "sse4.1")
+        {
+            // SAFETY: The conditions above ensure that all
+            //         required instructions are supported by the CPU.
+            Some(Self { state })
+        } else {
+            None
+        }
+    }
+
+    #[cfg(feature = "std")]
+    pub fn new(state: u32) -> Option<Self> {
+        if is_x86_feature_detected!("pclmulqdq")
+            && is_x86_feature_detected!("sse2")
+            && is_x86_feature_detected!("sse4.1")
+        {
+            // SAFETY: The conditions above ensure that all
+            //         required instructions are supported by the CPU.
+            Some(Self { state })
+        } else {
+            None
+        }
+    }
+
+    pub fn update(&mut self, buf: &[u8]) {
+        // SAFETY: The `State::new` constructor ensures that all
+        //         required instructions are supported by the CPU.
+        self.state = unsafe { calculate(self.state, buf) }
+    }
+
+    pub fn finalize(self) -> u32 {
+        self.state
+    }
+
+    pub fn reset(&mut self) {
+        self.state = 0;
+    }
+
+    pub fn combine(&mut self, other: u32, amount: u64) {
+        self.state = ::combine::combine(self.state, other, amount);
+    }
+}
+
+const K1: i64 = 0x154442bd4;
+const K2: i64 = 0x1c6e41596;
+const K3: i64 = 0x1751997d0;
+const K4: i64 = 0x0ccaa009e;
+const K5: i64 = 0x163cd6124;
+const K6: i64 = 0x1db710640;
+
+const P_X: i64 = 0x1DB710641;
+const U_PRIME: i64 = 0x1F7011641;
+
+#[cfg(feature = "std")]
+unsafe fn debug(s: &str, a: arch::__m128i) -> arch::__m128i {
+    if false {
+        union A {
+            a: arch::__m128i,
+            b: [u8; 16],
+        }
+        let x = A { a }.b;
+        print!(" {:20} | ", s);
+        for x in x.iter() {
+            print!("{:02x} ", x);
+        }
+        println!();
+    }
+    return a;
+}
+
+#[cfg(not(feature = "std"))]
+unsafe fn debug(_s: &str, a: arch::__m128i) -> arch::__m128i {
+    a
+}
+
+#[target_feature(enable = "pclmulqdq", enable = "sse2", enable = "sse4.1")]
+unsafe fn calculate(crc: u32, mut data: &[u8]) -> u32 {
+    // In theory we can accelerate smaller chunks too, but for now just rely on
+    // the fallback implementation as it's too much hassle and doesn't seem too
+    // beneficial.
+    if data.len() < 128 {
+        return ::baseline::update_fast_16(crc, data);
+    }
+
+    // Step 1: fold by 4 loop
+    let mut x3 = get(&mut data);
+    let mut x2 = get(&mut data);
+    let mut x1 = get(&mut data);
+    let mut x0 = get(&mut data);
+
+    // fold in our initial value, part of the incremental crc checksum
+    x3 = arch::_mm_xor_si128(x3, arch::_mm_cvtsi32_si128(!crc as i32));
+
+    let k1k2 = arch::_mm_set_epi64x(K2, K1);
+    while data.len() >= 64 {
+        x3 = reduce128(x3, get(&mut data), k1k2);
+        x2 = reduce128(x2, get(&mut data), k1k2);
+        x1 = reduce128(x1, get(&mut data), k1k2);
+        x0 = reduce128(x0, get(&mut data), k1k2);
+    }
+
+    let k3k4 = arch::_mm_set_epi64x(K4, K3);
+    let mut x = reduce128(x3, x2, k3k4);
+    x = reduce128(x, x1, k3k4);
+    x = reduce128(x, x0, k3k4);
+
+    // Step 2: fold by 1 loop
+    while data.len() >= 16 {
+        x = reduce128(x, get(&mut data), k3k4);
+    }
+
+    debug("128 > 64 init", x);
+
+    // Perform step 3, reduction from 128 bits to 64 bits. This is
+    // significantly different from the paper and basically doesn't follow it
+    // at all. It's not really clear why, but implementations of this algorithm
+    // in Chrome/Linux diverge in the same way. It is beyond me why this is
+    // different than the paper, maybe the paper has like errata or something?
+    // Unclear.
+    //
+    // It's also not clear to me what's actually happening here and/or why, but
+    // algebraically what's happening is:
+    //
+    // x = (x[0:63] • K4) ^ x[64:127]           // 96 bit result
+    // x = ((x[0:31] as u64) • K5) ^ x[32:95]   // 64 bit result
+    //
+    // It's... not clear to me what's going on here. The paper itself is pretty
+    // vague on this part but definitely uses different constants at least.
+    // It's not clear to me, reading the paper, where the xor operations are
+    // happening or why things are shifting around. This implementation...
+    // appears to work though!
+    drop(K6);
+    let x = arch::_mm_xor_si128(
+        arch::_mm_clmulepi64_si128(x, k3k4, 0x10),
+        arch::_mm_srli_si128(x, 8),
+    );
+    let x = arch::_mm_xor_si128(
+        arch::_mm_clmulepi64_si128(
+            arch::_mm_and_si128(x, arch::_mm_set_epi32(0, 0, 0, !0)),
+            arch::_mm_set_epi64x(0, K5),
+            0x00,
+        ),
+        arch::_mm_srli_si128(x, 4),
+    );
+    debug("128 > 64 xx", x);
+
+    // Perform a Barrett reduction from our now 64 bits to 32 bits. The
+    // algorithm for this is described at the end of the paper, and note that
+    // this also implements the "bit reflected input" variant.
+    let pu = arch::_mm_set_epi64x(U_PRIME, P_X);
+
+    // T1(x) = ⌊(R(x) % x^32)⌋ • μ
+    let t1 = arch::_mm_clmulepi64_si128(
+        arch::_mm_and_si128(x, arch::_mm_set_epi32(0, 0, 0, !0)),
+        pu,
+        0x10,
+    );
+    // T2(x) = ⌊(T1(x) % x^32)⌋ • P(x)
+    let t2 = arch::_mm_clmulepi64_si128(
+        arch::_mm_and_si128(t1, arch::_mm_set_epi32(0, 0, 0, !0)),
+        pu,
+        0x00,
+    );
+    // We're doing the bit-reflected variant, so get the upper 32-bits of the
+    // 64-bit result instead of the lower 32-bits.
+    //
+    // C(x) = R(x) ^ T2(x) / x^32
+    let c = arch::_mm_extract_epi32(arch::_mm_xor_si128(x, t2), 1) as u32;
+
+    if !data.is_empty() {
+        ::baseline::update_fast_16(!c, data)
+    } else {
+        !c
+    }
+}
+
+unsafe fn reduce128(a: arch::__m128i, b: arch::__m128i, keys: arch::__m128i) -> arch::__m128i {
+    let t1 = arch::_mm_clmulepi64_si128(a, keys, 0x00);
+    let t2 = arch::_mm_clmulepi64_si128(a, keys, 0x11);
+    arch::_mm_xor_si128(arch::_mm_xor_si128(b, t1), t2)
+}
+
+unsafe fn get(a: &mut &[u8]) -> arch::__m128i {
+    debug_assert!(a.len() >= 16);
+    let r = arch::_mm_loadu_si128(a.as_ptr() as *const arch::__m128i);
+    *a = &a[16..];
+    return r;
+}
+
+#[cfg(test)]
+mod test {
+    quickcheck! {
+        fn check_against_baseline(init: u32, chunks: Vec<(Vec<u8>, usize)>) -> bool {
+            let mut baseline = super::super::super::baseline::State::new(init);
+            let mut pclmulqdq = super::State::new(init).expect("not supported");
+            for (chunk, mut offset) in chunks {
+                // simulate random alignments by offsetting the slice by up to 15 bytes
+                offset &= 0xF;
+                if chunk.len() <= offset {
+                    baseline.update(&chunk);
+                    pclmulqdq.update(&chunk);
+                } else {
+                    baseline.update(&chunk[offset..]);
+                    pclmulqdq.update(&chunk[offset..]);
+                }
+            }
+            pclmulqdq.finalize() == baseline.finalize()
+        }
+    }
+}