Add example of inline assembly

Author: Amanieu

src/inline-assembly.md

@@ -6,6 +6,23 @@ It can be used to embed handwritten assembly in the assembly output generated by
 [`asm!`]: ../core/arch/macro.asm.html
 [`global_asm!`]: ../core/arch/macro.global_asm.html
 
+```rust
+#![feature(asm)]
+// Multiply x by 6 using shifts and adds
+let mut x: u64 = 4;
+unsafe {
+    asm!(
+        "mov {tmp}, {x}",
+        "shl {tmp}, 1",
+        "shl {x}, 2",
+        "add {x}, {tmp}",
+        x = inout(reg) x,
+        tmp = out(reg) _,
+    );
+}
+assert_eq!(x, 4 * 6);
+```
+
 The following ABNF specifies the general syntax:
 
 ```text