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authorStephen Hines <srhines@google.com>2014-07-21 00:45:20 -0700
committerStephen Hines <srhines@google.com>2014-07-21 00:45:20 -0700
commitc6a4f5e819217e1e12c458aed8e7b122e23a3a58 (patch)
tree81b7dd2bb4370a392f31d332a566c903b5744764 /docs/Extensions.rst
parent19c6fbb3e8aaf74093afa08013134b61fa08f245 (diff)
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Update LLVM for rebase to r212749.
Includes a cherry-pick of: r212948 - fixes a small issue with atomic calls Change-Id: Ib97bd980b59f18142a69506400911a6009d9df18
Diffstat (limited to 'docs/Extensions.rst')
-rw-r--r--docs/Extensions.rst49
1 files changed, 34 insertions, 15 deletions
diff --git a/docs/Extensions.rst b/docs/Extensions.rst
index a49485c..271c085 100644
--- a/docs/Extensions.rst
+++ b/docs/Extensions.rst
@@ -76,7 +76,7 @@ the target. It corresponds to the COFF relocation types
Syntax:
- ``.linkonce [ comdat type [ section identifier ] ]``
+ ``.linkonce [ comdat type ]``
Supported COMDAT types:
@@ -95,16 +95,6 @@ Supported COMDAT types:
Duplicates are discarded, but the linker issues an error if any duplicates
do not have exactly the same content.
-``associative``
- Links the section if a certain other COMDAT section is linked. This other
- section is indicated by its section identifier following the comdat type.
- The following restrictions apply to the associated section:
-
- 1. It must be the name of a section already defined.
- 2. It must differ from the current section.
- 3. It must be a COMDAT section.
- 4. It cannot be another associative COMDAT section.
-
``largest``
Links the largest section from among the duplicates.
@@ -118,10 +108,6 @@ Supported COMDAT types:
.linkonce
...
- .section .xdata$foo
- .linkonce associative .text$foo
- ...
-
``.section`` Directive
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -160,6 +146,25 @@ different COMDATs:
Symbol2:
.long 1
+In addition to the types allowed with ``.linkonce``, ``.section`` also accepts
+``associative``. The meaning is that the section is linked if a certain other
+COMDAT section is linked. This other section is indicated by the comdat symbol
+in this directive. It can be any symbol defined in the associated section, but
+is usually the associated section's comdat.
+
+ The following restrictions apply to the associated section:
+
+ 1. It must be a COMDAT section.
+ 2. It cannot be another associative COMDAT section.
+
+In the following example the symobl ``sym`` is the comdat symbol of ``.foo``
+and ``.bar`` is associated to ``.foo``.
+
+.. code-block:: gas
+
+ .section .foo,"bw",discard, "sym"
+ .section .bar,"rd",associative, "sym"
+
Target Specific Behaviour
=========================
@@ -190,3 +195,17 @@ range via a slight deviation. It will generate an indirect jump as follows:
blx r12
sub.w sp, sp, r4
+Variable Length Arrays
+^^^^^^^^^^^^^^^^^^^^^^
+
+The reference implementation (Microsoft Visual Studio 2012) does not permit the
+emission of Variable Length Arrays (VLAs).
+
+The Windows ARM Itanium ABI extends the base ABI by adding support for emitting
+a dynamic stack allocation. When emitting a variable stack allocation, a call
+to ``__chkstk`` is emitted unconditionally to ensure that guard pages are setup
+properly. The emission of this stack probe emission is handled similar to the
+standard stack probe emission.
+
+The MSVC environment does not emit code for VLAs currently.
+