Add example of inline assembly

Author: Amanieu

src/inline-assembly.md

@@ -6,6 +6,35 @@ 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
 
+Support for inline assembly is stable on the following architectures:
+- x86 and x86-64
+- ARM
+- AArch64
+- RISC-V
+
+The compiler will emit an error if `asm!` is used on an unsupported target.
+
+## Example
+
+```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);
+```
+
+## Syntax
+
 The following ABNF specifies the general syntax:
 
 ```text
@@ -21,13 +50,6 @@ asm := "asm!(" format_string *("," format_string) *("," [ident "="] operand) *("
 global_asm := "global_asm!(" format_string *("," format_string) *("," [ident "="] operand) *("," options) [","] ")"
 ```
 
-Support for inline assembly is stable on the following architectures:
-- x86 and x86-64
-- ARM
-- AArch64
-- RISC-V
-
-The compiler will emit an error if `asm!` is used on an unsupported target.
 
 ## Scope