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| author | Dimitry Andric <dim@FreeBSD.org> | 2017-12-24 01:00:08 +0000 |
|---|---|---|
| committer | Dimitry Andric <dim@FreeBSD.org> | 2017-12-24 01:00:08 +0000 |
| commit | c7dac04c3480f3c20487f912f77343139fce2d99 (patch) | |
| tree | 21a09bce0171e27bd1e92649db9df797fa097cea /docs/Extensions.rst | |
| parent | 044eb2f6afba375a914ac9d8024f8f5142bb912e (diff) | |
Diffstat (limited to 'docs/Extensions.rst')
| -rw-r--r-- | docs/Extensions.rst | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/docs/Extensions.rst b/docs/Extensions.rst index 14fea30204b4..32eeadd78ba6 100644 --- a/docs/Extensions.rst +++ b/docs/Extensions.rst @@ -288,3 +288,31 @@ standard stack probe emission. The MSVC environment does not emit code for VLAs currently. +Windows on ARM64 +---------------- + +Stack Probe Emission +^^^^^^^^^^^^^^^^^^^^ + +The reference implementation (Microsoft Visual Studio 2017) emits stack probes +in the following fashion: + +.. code-block:: gas + + mov x15, #constant + bl __chkstk + sub sp, sp, x15, lsl #4 + +However, this has the limitation of 256 MiB (±128MiB). In order to accommodate +larger binaries, LLVM supports the use of ``-mcode-model=large`` to allow a 8GiB +(±4GiB) range via a slight deviation. It will generate an indirect jump as +follows: + +.. code-block:: gas + + mov x15, #constant + adrp x16, __chkstk + add x16, x16, :lo12:__chkstk + blr x16 + sub sp, sp, x15, lsl #4 + |