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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 + |