[libc-commits] [libc] [libc][arm] implement a basic setjmp/longjmp (PR #93220)

[Nick Desaulniers via libc-commits]

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@@ -0,0 +1,26 @@
+
+//===-- Implementation of longjmp -----------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/setjmp/longjmp.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+[[gnu::naked]]
+LLVM_LIBC_FUNCTION(void, longjmp, (__jmp_buf * buf, int val)) {
+  asm(R"(
+      ldm r0, {r4-r12, lr}
----------------
nickdesaulniers wrote:

This code is restoring r4-r11, sp, and lr from the memory referred to by `buf`.

It then returns `1` if `val` was zero, else `val`.  Since `lr` was restored, it doesn't return to the caller of `longjmp`, but instead the caller of `setjmp`.

https://github.com/llvm/llvm-project/pull/93220