Make names of types used in LLVM IR stable.

Before this PR, type names could depend on the cratenum being used
for a given crate and also on the source location of closures.
Both are undesirable for incremental compilation where we cache
LLVM IR and don't want it to depend on formatting or in which
order crates are loaded.

2 files changed, 65 insertions, 0 deletions

diff --git a/src/librustc_data_structures/base_n.rs b/src/librustc_data_structures/base_n.rs
new file mode 100644
index 00000000000..bf3e682f86f
--- /dev/null
+++ b/src/librustc_data_structures/base_n.rs
@@ -0,0 +1,64 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+/// Convert unsigned integers into a string representation with some base.
+/// Bases up to and including 36 can be used for case-insensitive things.
+
+use std::str;
+
+pub const MAX_BASE: u64 = 64;
+const BASE_64: &'static [u8; MAX_BASE as usize] =
+    b"0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ@$";
+
+#[inline]
+pub fn push_str(mut n: u64, base: u64, output: &mut String) {
+    debug_assert!(base >= 2 && base <= MAX_BASE);
+    let mut s = [0u8; 64];
+    let mut index = 0;
+
+    loop {
+        s[index] = BASE_64[(n % base) as usize];
+        index += 1;
+        n /= base;
+
+        if n == 0 {
+            break;
+        }
+    }
+    &mut s[0..index].reverse();
+    output.push_str(str::from_utf8(&s[0..index]).unwrap());
+}
+
+#[inline]
+pub fn encode(n: u64, base: u64) -> String {
+    let mut s = String::with_capacity(13);
+    push_str(n, base, &mut s);
+    s
+}
+
+#[test]
+fn test_encode() {
+    fn test(n: u64, base: u64) {
+        assert_eq!(Ok(n), u64::from_str_radix(&encode(n, base)[..], base as u32));
+    }
+
+    for base in 2..37 {
+        test(0, base);
+        test(1, base);
+        test(35, base);
+        test(36, base);
+        test(37, base);
+        test(u64::max_value(), base);
+
+        for i in 0 .. 1_000 {
+            test(i * 983, base);
+        }
+    }
+}
diff --git a/src/librustc_data_structures/lib.rs b/src/librustc_data_structures/lib.rs
index 2e4206d2ee1..de13b9bf4be 100644
--- a/src/librustc_data_structures/lib.rs
+++ b/src/librustc_data_structures/lib.rs
@@ -47,6 +47,7 @@ extern crate libc;
 pub mod array_vec;
 pub mod accumulate_vec;
 pub mod small_vec;
+pub mod base_n;
 pub mod bitslice;
 pub mod blake2b;
 pub mod bitvec;