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Diffstat (limited to 'docs/Extensions.rst')
| -rw-r--r-- | docs/Extensions.rst | 31 |
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diff --git a/docs/Extensions.rst b/docs/Extensions.rst index 7d8c521..a49485c 100644 --- a/docs/Extensions.rst +++ b/docs/Extensions.rst @@ -159,3 +159,34 @@ different COMDATs: .globl Symbol2 Symbol2: .long 1 + +Target Specific Behaviour +========================= + +Windows on ARM +-------------- + +Stack Probe Emission +^^^^^^^^^^^^^^^^^^^^ + +The reference implementation (Microsoft Visual Studio 2012) emits stack probes +in the following fashion: + +.. code-block:: gas + + movw r4, #constant + bl __chkstk + sub.w sp, sp, r4 + +However, this has the limitation of 32 MiB (±16MiB). In order to accommodate +larger binaries, LLVM supports the use of ``-mcode-model=large`` to allow a 4GiB +range via a slight deviation. It will generate an indirect jump as follows: + +.. code-block:: gas + + movw r4, #constant + movw r12, :lower16:__chkstk + movt r12, :upper16:__chkstk + blx r12 + sub.w sp, sp, r4 + |