From 9c025d7e0439e97fcec7a3977e39c152fd88d1df Mon Sep 17 00:00:00 2001
From: Jan Niehusmann <jan@gondor.com>
Date: Tue, 15 Apr 2025 14:57:50 +0000
Subject: [PATCH] Remove lr::write() function, and add comment to lr::read()
 function.

Fixes #570
---
 cortex-m/src/register/lr.rs | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/cortex-m/src/register/lr.rs b/cortex-m/src/register/lr.rs
index 02708ae4..5752ff72 100644
--- a/cortex-m/src/register/lr.rs
+++ b/cortex-m/src/register/lr.rs
@@ -4,6 +4,9 @@
 use core::arch::asm;
 
 /// Reads the CPU register
+///
+/// Note that this function can't be used reliably: The value returned at least depends
+/// on whether the compiler chooses to inline the function or not.
 #[cfg(cortex_m)]
 #[inline]
 pub fn read() -> u32 {
@@ -12,9 +15,4 @@ pub fn read() -> u32 {
     r
 }
 
-/// Writes `bits` to the CPU register
-#[cfg(cortex_m)]
-#[inline]
-pub unsafe fn write(bits: u32) {
-    asm!("mov lr, {}", in(reg) bits, options(nomem, nostack, preserves_flags));
-}
+// No `write` function for the LR register, as it can't be used soundly.