benches: Add benchmarks for mem* functions

This allows comparing the "normal" implementations to the
implementations provided by this crate.

Signed-off-by: Joe Richey <joerichey@google.com>

testcrate/benches/mem.rs

@@ -0,0 +1,154 @@
+#![feature(test)]
+
+extern crate test;
+use test::{black_box, Bencher};
+
+extern crate compiler_builtins;
+use compiler_builtins::mem::{memcmp, memcpy, memset, memmove};
+
+fn memcpy_builtin(b: &mut Bencher, n: usize) {
+    let v1 = vec![1u8; n];
+    let mut v2 = vec![0u8; n];
+    b.iter(|| {
+        let src: &[u8] = black_box(&v1);
+        let dst: &mut [u8] = black_box(&mut v2);
+        dst.copy_from_slice(src);
+    })
+}
+
+fn memcpy_rust(b: &mut Bencher, n: usize) {
+    let v1 = vec![1u8; n];
+    let mut v2 = vec![0u8; n];
+    b.iter(|| {
+        let src: &[u8] = black_box(&v1);
+        let dst: &mut [u8] = black_box(&mut v2);
+        unsafe { memcpy(dst.as_mut_ptr(), src.as_ptr(), n) }
+    })
+}
+
+fn memset_builtin(b: &mut Bencher, n: usize) {
+    let mut v1 = vec![0u8; n];
+    b.iter(|| {
+        let dst: &mut [u8] = black_box(&mut v1);
+        let val: u8 = black_box(27);
+        for b in dst {
+            *b = val;
+        }
+    })
+}
+
+fn memset_rust(b: &mut Bencher, n: usize) {
+    let mut v1 = vec![0u8; n];
+    b.iter(|| {
+        let dst: &mut [u8] = black_box(&mut v1);
+        let val = black_box(27);
+        unsafe { memset(dst.as_mut_ptr(), val, n) }
+    })
+}
+
+fn memcmp_builtin(b: &mut Bencher, n: usize) {
+    let v1 = vec![0u8; n];
+    let mut v2 = vec![0u8; n];
+    v2[n - 1] = 1;
+    b.iter(|| {
+        let s1: &[u8] = black_box(&v1);
+        let s2: &[u8] = black_box(&v2);
+        s1.cmp(s2)
+    })
+}
+
+fn memcmp_rust(b: &mut Bencher, n: usize) {
+    let v1 = vec![0u8; n];
+    let mut v2 = vec![0u8; n];
+    v2[n - 1] = 1;
+    b.iter(|| {
+        let s1: &[u8] = black_box(&v1);
+        let s2: &[u8] = black_box(&v2);
+        unsafe { memcmp(s1.as_ptr(), s2.as_ptr(), n) }
+    })
+}
+
+fn memmove_builtin(b: &mut Bencher, n: usize) {
+    let mut v = vec![0u8; n+n/2];
+    b.iter(|| {
+        let s: &mut [u8] = black_box(&mut v);
+        s.copy_within(0..n, n/2);
+    })
+}
+
+fn memmove_rust(b: &mut Bencher, n: usize) {
+    let mut v = vec![0u8; n+n/2];
+    b.iter(|| {
+        let dst: *mut u8 = black_box(&mut v[n/2..]).as_mut_ptr();
+        let src: *const u8 = black_box(&v).as_ptr();
+        unsafe { memmove(dst, src, n) };
+    })
+}
+
+#[bench]
+fn memcpy_builtin_4096(b: &mut Bencher) {
+    memcpy_builtin(b, 4096)
+}
+#[bench]
+fn memcpy_rust_4096(b: &mut Bencher) {
+    memcpy_rust(b, 4096)
+}
+#[bench]
+fn memcpy_builtin_1048576(b: &mut Bencher) {
+    memcpy_builtin(b, 1048576)
+}
+#[bench]
+fn memcpy_rust_1048576(b: &mut Bencher) {
+    memcpy_rust(b, 1048576)
+}
+
+#[bench]
+fn memset_builtin_4096(b: &mut Bencher) {
+    memset_builtin(b, 4096)
+}
+#[bench]
+fn memset_rust_4096(b: &mut Bencher) {
+    memset_rust(b, 4096)
+}
+#[bench]
+fn memset_builtin_1048576(b: &mut Bencher) {
+    memset_builtin(b, 1048576)
+}
+#[bench]
+fn memset_rust_1048576(b: &mut Bencher) {
+    memset_rust(b, 1048576)
+}
+
+#[bench]
+fn memcmp_builtin_4096(b: &mut Bencher) {
+    memcmp_builtin(b, 4096)
+}
+#[bench]
+fn memcmp_rust_4096(b: &mut Bencher) {
+    memcmp_rust(b, 4096)
+}
+#[bench]
+fn memcmp_builtin_1048576(b: &mut Bencher) {
+    memcmp_builtin(b, 1048576)
+}
+#[bench]
+fn memcmp_rust_1048576(b: &mut Bencher) {
+    memcmp_rust(b, 1048576)
+}
+
+#[bench]
+fn memmove_builtin_4096(b: &mut Bencher) {
+    memmove_builtin(b, 4096)
+}
+#[bench]
+fn memmove_rust_4096(b: &mut Bencher) {
+    memmove_rust(b, 4096)
+}
+#[bench]
+fn memmove_builtin_1048576(b: &mut Bencher) {
+    memmove_builtin(b, 1048576)
+}
+#[bench]
+fn memmove_rust_1048576(b: &mut Bencher) {
+    memmove_rust(b, 1048576)
+}