[libc-commits] [libc] [libc] implement sigsetjmp for thumb/thumb2/armv7-a (PR #138147)

[Schrodinger ZHU Yifan via libc-commits]

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@@ -0,0 +1,65 @@
+//===-- Implementation of sigsetjmp ---------------------------------------===//
+//
+// 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/sigsetjmp.h"
+#include "hdr/offsetof_macros.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+#include "src/setjmp/setjmp_impl.h"
+#include "src/setjmp/sigsetjmp_epilogue.h"
+
+namespace LIBC_NAMESPACE_DECL {
+[[gnu::naked]]
+LLVM_LIBC_FUNCTION(int, sigsetjmp, (sigjmp_buf buf)) {
+#if defined(__thumb__) && __ARM_ARCH_ISA_THUMB == 1
+  // Thumb1 does not support the high registers > r7 in stmia, so move them
+  // into lower GPRs first.
+  asm(R"(
+      tst r1, r1
+      bne .Ldosave
+      b %c[setjmp]
+.Ldosave:
+      str r4, [r0, #%c[extra]]
+      mov r4, lr
+      str r4, [r0, #%c[retaddr]]
+      mov r4, r0
+      bl %c[setjmp]
+      mov r1, r0
+      mov r0, r4
+      ldr r4, [r0, #%c[retaddr]]
+      mov lr, r4
+      ldr r4, [r0, #%c[extra]]
+      b %c[epilogue]
+  )" ::[retaddr] "i"(offsetof(__jmp_buf, sig_retaddr)),
+      [extra] "i"(offsetof(__jmp_buf, sig_extra)), [setjmp] "i"(setjmp),
+      [epilogue] "i"(sigsetjmp_epilogue)
+      : "r0", "r1", "r4");
+#else
+  // Some thumb2 linkers do not support conditional branch to PLT.
+  // We branch to local labels instead.
+  asm(R"(
+      tst r1, r1
+      bne .Ldosave
+      b %c[setjmp]
+.Ldosave:
+      str r4, [r0, #%c[extra]]
+      str lr, [r0, #%c[retaddr]]
+      mov r4, r0
+      bl %c[setjmp]
+      mov r1, r0
+      mov r0, r4
+      ldr r4, [r0, #%c[retaddr]]
+      ldr lr, [r0, #%c[extra]]
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SchrodingerZhu wrote:

good catch

https://github.com/llvm/llvm-project/pull/138147