From 3ba1035d279e0acfc3aaf68e8bd055f2d1ffb205 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Mon, 7 Sep 2020 11:26:24 +0200
Subject: [PATCH] use standard black_box function

---
 tests/compile-fail/invalid_bool.rs | 6 ++----
 tests/run-pass/float.rs            | 7 ++-----
 tests/run-pass/u128.rs             | 3 ++-
 3 files changed, 6 insertions(+), 10 deletions(-)

diff --git a/tests/compile-fail/invalid_bool.rs b/tests/compile-fail/invalid_bool.rs
index 8d8cce1c7e5..796d8220dc1 100644
--- a/tests/compile-fail/invalid_bool.rs
+++ b/tests/compile-fail/invalid_bool.rs
@@ -1,11 +1,9 @@
 // Validation makes this fail in the wrong place
 // Make sure we find these even with many checks disabled.
 // compile-flags: -Zmiri-disable-alignment-check -Zmiri-disable-stacked-borrows -Zmiri-disable-validation
-
-#[inline(never)]
-fn dont_optimize<T>(x: T) -> T { x }
+#![feature(test)]
 
 fn main() {
     let b = unsafe { std::mem::transmute::<u8, bool>(2) };
-    let _x = b == dont_optimize(true); //~ ERROR interpreting an invalid 8-bit value as a bool: 0x02
+    let _x = b == std::hint::black_box(true); //~ ERROR interpreting an invalid 8-bit value as a bool: 0x02
 }
diff --git a/tests/run-pass/float.rs b/tests/run-pass/float.rs
index ea6269c22fb..327ea17731a 100644
--- a/tests/run-pass/float.rs
+++ b/tests/run-pass/float.rs
@@ -1,7 +1,8 @@
 // compile-flags: -Zmir-opt-level=0
 // FIXME: Using opt-level 2 here makes the test take forever (https://github.com/rust-lang/rust/issues/76433).
-#![feature(stmt_expr_attributes)]
+#![feature(stmt_expr_attributes, test)]
 use std::fmt::Debug;
+use std::hint::black_box;
 
 // Helper function to avoid promotion so that this tests "run-time" casts, not CTFE.
 // Doesn't make a big difference when running this in Miri, but it means we can compare this
@@ -341,10 +342,6 @@ fn ops() {
 /// Tests taken from rustc test suite.
 ///
 
-// Poor-man's black-box
-#[inline(never)]
-fn black_box<T>(x: T) -> T { x }
-
 macro_rules! test {
     ($val:expr, $src_ty:ident -> $dest_ty:ident, $expected:expr) => (
         // black_box disables constant evaluation to test run-time conversions:
diff --git a/tests/run-pass/u128.rs b/tests/run-pass/u128.rs
index a2ca7746b1c..bbc667c5dde 100644
--- a/tests/run-pass/u128.rs
+++ b/tests/run-pass/u128.rs
@@ -1,4 +1,5 @@
-fn b<T>(t: T) -> T { t }
+#![feature(test)]
+use std::hint::black_box as b;
 
 fn main() {
     let x: u128 = 0xFFFF_FFFF_FFFF_FFFF__FFFF_FFFF_FFFF_FFFF;
-- 
2.44.0