Rename blackBox, move it to std.mem.forceEval()

This commit is contained in:
Frank Denis 2020-08-25 22:43:42 +02:00
parent ff2e82f382
commit 0bd53dd203
3 changed files with 19 additions and 40 deletions

View File

@ -7,6 +7,7 @@
const builtin = @import("builtin");
const std = @import("std");
const mem = std.mem;
const time = std.time;
const Timer = time.Timer;
const crypto = std.crypto;
@ -21,14 +22,6 @@ const Crypto = struct {
name: []const u8,
};
fn blackBox(x: anytype) void {
asm volatile (""
:
: [x] "rm" (x)
: "memory"
);
}
const hashes = [_]Crypto{
Crypto{ .ty = crypto.hash.Md5, .name = "md5" },
Crypto{ .ty = crypto.hash.Sha1, .name = "sha1" },
@ -54,7 +47,7 @@ pub fn benchmarkHash(comptime Hash: anytype, comptime bytes: comptime_int) !u64
while (offset < bytes) : (offset += block.len) {
h.update(block[0..]);
}
blackBox(&h);
mem.forceEval(&h);
const end = timer.read();
const elapsed_s = @intToFloat(f64, end - start) / time.ns_per_s;
@ -89,7 +82,7 @@ pub fn benchmarkMac(comptime Mac: anytype, comptime bytes: comptime_int) !u64 {
const start = timer.lap();
while (offset < bytes) : (offset += in.len) {
Mac.create(mac[0..], in[0..], key[0..]);
blackBox(&mac);
mem.forceEval(&mac);
}
const end = timer.read();
@ -116,7 +109,7 @@ pub fn benchmarkKeyExchange(comptime DhKeyExchange: anytype, comptime exchange_c
var i: usize = 0;
while (i < exchange_count) : (i += 1) {
_ = DhKeyExchange.create(out[0..], out[0..], in[0..]);
blackBox(&out);
mem.forceEval(&out);
}
}
const end = timer.read();
@ -141,7 +134,7 @@ pub fn benchmarkSignature(comptime Signature: anytype, comptime signatures_count
var i: usize = 0;
while (i < signatures_count) : (i += 1) {
const s = try Signature.sign(&msg, key_pair, null);
blackBox(&s);
mem.forceEval(&s);
}
}
const end = timer.read();
@ -177,7 +170,7 @@ pub fn benchmarkAead(comptime Aead: anytype, comptime bytes: comptime_int) !u64
Aead.encrypt(in[0..], tag[0..], in[0..], &[_]u8{}, nonce, key);
Aead.decrypt(in[0..], in[0..], tag, &[_]u8{}, nonce, key) catch unreachable;
}
blackBox(&in);
mem.forceEval(&in);
const end = timer.read();
const elapsed_s = @intToFloat(f64, end - start) / time.ns_per_s;

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@ -5,6 +5,7 @@
// and substantial portions of the software.
const std = @import("std.zig");
const assert = std.debug.assert;
const mem = std.mem;
const testing = std.testing;
/// Euler's number (e)
@ -108,34 +109,8 @@ pub fn approxEq(comptime T: type, x: T, y: T, epsilon: T) bool {
return fabs(x - y) < epsilon;
}
// TODO: Hide the following in an internal module.
pub fn forceEval(value: anytype) void {
const T = @TypeOf(value);
switch (T) {
f16 => {
var x: f16 = undefined;
const p = @ptrCast(*volatile f16, &x);
p.* = x;
},
f32 => {
var x: f32 = undefined;
const p = @ptrCast(*volatile f32, &x);
p.* = x;
},
f64 => {
var x: f64 = undefined;
const p = @ptrCast(*volatile f64, &x);
p.* = x;
},
f128 => {
var x: f128 = undefined;
const p = @ptrCast(*volatile f128, &x);
p.* = x;
},
else => {
@compileError("forceEval not implemented for " ++ @typeName(T));
},
}
mem.forceEval(value);
}
pub fn raiseInvalid() void {

View File

@ -2158,6 +2158,17 @@ pub fn alignForwardGeneric(comptime T: type, addr: T, alignment: T) T {
return alignBackwardGeneric(T, addr + (alignment - 1), alignment);
}
/// Force an evaluation of the expression; this tries to prevent
/// the compiler from optimizing the computation away even if the
/// result eventually gets discarded.
pub fn forceEval(val: anytype) void {
asm volatile (""
:
: [val] "rm" (val)
: "memory"
);
}
test "alignForward" {
testing.expect(alignForward(1, 1) == 1);
testing.expect(alignForward(2, 1) == 2);