[libunwind] Fix build error because of wrong register size

[medismailben]

This patch should fix an libunwind build failure that happens on Chromium's Android bots:

#165066 (comment)

The issue is that we're using the wzr register to move the value 0 in x1, but this is the 32-bit register.

To prevent this issue, we use an immediate instead of the zero registers.

[llvmbot]

@llvm/pr-subscribers-libunwind

Author: Med Ismail Bennani (medismailben)

Changes

This patch should fix an libunwind build failure that happens on Chromium's Android bots:

#165066 (comment)

The issue is that we're using the wzr register to move the value 0 in x1, but this is the 32-bit register. We should be using the 64-bit version, xzr instead.

---

Full diff: https://github.com/llvm/llvm-project/pull/167743.diff

1 Files Affected:

• (modified) libunwind/src/UnwindLevel1.c (+1-1)

diff --git a/libunwind/src/UnwindLevel1.c b/libunwind/src/UnwindLevel1.c
index 79398bac8b531..f1794ef2bb49e 100644
--- a/libunwind/src/UnwindLevel1.c
+++ b/libunwind/src/UnwindLevel1.c
@@ -82,7 +82,7 @@
     void *shstkRegContext = __libunwind_shstk_get_registers((cursor));         \
     void *shstkJumpAddress = __libunwind_shstk_get_jump_target();              \
     __asm__ volatile("mov x0, %0\n\t"                                          \
-                     "mov x1, wzr\n\t"                                         \
+                     "mov x1, xzr\n\t"                                         \
                      "br %1\n\t"                                               \
                      :                                                         \
                      : "r"(shstkRegContext), "r"(shstkJumpAddress)             \

[dtellenbach]

LGTM with the nit of using an immediate instead.

[github-actions]

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You can test this locally with the following command:

git-clang-format --diff origin/main HEAD --extensions c -- libunwind/src/UnwindLevel1.c --diff_from_common_commit

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View the diff from clang-format here.

diff --git a/libunwind/src/UnwindLevel1.c b/libunwind/src/UnwindLevel1.c
index 73a27928e..714f0b7d3 100644
--- a/libunwind/src/UnwindLevel1.c
+++ b/libunwind/src/UnwindLevel1.c
@@ -82,7 +82,7 @@
     void *shstkRegContext = __libunwind_shstk_get_registers((cursor));         \
     void *shstkJumpAddress = __libunwind_shstk_get_jump_target();              \
     __asm__ volatile("mov x0, %0\n\t"                                          \
-                     "mov x1, #0\n\t"                                         \
+                     "mov x1, #0\n\t"                                          \
                      "br %1\n\t"                                               \
                      :                                                         \
                      : "r"(shstkRegContext), "r"(shstkJumpAddress)             \