[libunwind] [libunwind] Add support for the AArch64 "Vector Granule" (VG) register (PR #153565)

[Fangrui Song via cfe-commits]

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@@ -0,0 +1,66 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: linux && target={{aarch64-.+}}
+
+#include <libunwind.h>
+#include <stdlib.h>
+#include <string.h>
+
+// Basic test of VG (Vector Granule) unwinding. This is meant to mimic SVE/SME
+// unwind info without requiring those features for this test.
+
+#define VG_REGNUM 46
+
+__attribute__((noinline)) void baz() {
+  // The previous value of VG is 2
+  asm volatile(".cfi_escape 0x16, 0x2e, 0x01, 0x32");
+
+  unw_context_t context;
+  unw_cursor_t cursor;
+  unw_getcontext(&context);
+  unw_init_local(&cursor, &context);
+
+  // Note: At this point VG is not defined (until we unw_step).
+
+  uint16_t expected_vgs[]{/*qux*/ 2, /*bar*/ 2, /*foo*/ 8, /*main*/ 2};
+  for (uint16_t expected_vg : expected_vgs) {
+    unw_step(&cursor);
+    unw_word_t vg;
+    unw_get_reg(&cursor, VG_REGNUM, &vg);
+    if (vg != expected_vg)
+      exit(1);
+  }
+  exit(0);
+}
+
+__attribute__((noinline)) void qux() { baz(); }
+
+__attribute__((noinline)) void bar() {
+  // The previous value of VG is 8
+  asm volatile(".cfi_escape 0x16, 0x2e, 0x01, 0x38");
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MaskRay wrote:

asm statements that have no output operands are implicitly volatile.

Delete `volatile`.

https://github.com/llvm/llvm-project/pull/153565