Fix black_box bug detected by Amanieu

tesuji · Amanieu · tesuji · commit 4dc4e9f671a3 · 2020-09-16T09:25:54.000Z
Co-authored-by: Amanieu &lt;amanieu@gmail.com&gt;
diff --git a/library/core/src/hint.rs b/library/core/src/hint.rs
@@ -122,7 +122,7 @@ pub fn black_box<T>(mut dummy: T) -> T {
     // SAFETY: the inline assembly is a no-op.
     unsafe {
         // FIXME: Cannot use `asm!` because it doesn't support MIPS and other architectures.
-        llvm_asm!("" : : "r"(&mut dummy));
+        llvm_asm!("" : : "r"(&mut dummy) : "memory" : "volatile");
     }
 
     dummy

Original file line number	Diff line number	Diff line change
`@@ -122,7 +122,7 @@ pub fn black_box<T>(mut dummy: T) -> T {`
`122`	`122`	`// SAFETY: the inline assembly is a no-op.`
`123`	`123`	`unsafe {`
`124`	`124`	// FIXME: Cannot use `asm!` because it doesn't support MIPS and other architectures.
`125`		`- llvm_asm!("" : : "r"(&mut dummy));`
	`125`	`+ llvm_asm!("" : : "r"(&mut dummy) : "memory" : "volatile");`
`126`	`126`	`}`
`127`	`127`
`128`	`128`	`dummy`