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Add platform specific tests doc

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185581 91177308-0d34-0410-b5e6-96231b3b80d8
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Renato Golin 2013-07-03 20:56:33 +00:00
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docs/TestingGuide.rst
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@ -275,6 +275,66 @@ This test will fail if placed into a ``download`` directory.
To make your tests robust, always use ``opt ... < %s`` in the RUN line.
:program:`opt` does not output a ``ModuleID`` when input comes from stdin.
Platform-Specific Tests
-----------------------
Whenever adding tests that require the knowledge of a specific platform,
either related to code generated, specific output or back-end features,
you must make sure to isolate the features, so that buildbots that
run on different architectures (and don't even compile all back-ends),
don't fail.
The first problem is to check for target-specific output, for example sizes
of structures, paths and architecture names, for example:
* Tests containing Windows paths will fail on Linux and vice-versa.
* Tests that check for ``x86_64`` somewhere in the text will fail anywhere else.
* Tests where the debug information calculates the size of types and structures.
Also, if the test rely on any behaviour that is coded in any back-end, it must
go in its own directory. So, for instance, code generator tests for ARM go
into ``test/CodeGen/ARM`` and so on. Those directories contain a special
``lit`` configuration file that ensure all tests in that directory will
only run if a specific back-end is compiled and available.
For instance, on ``test/CodeGen/ARM``, the ``lit.local.cfg`` is:
.. code-block:: python
config.suffixes = ['.ll', '.c', '.cpp', '.test']
targets = set(config.root.targets_to_build.split())
if not 'ARM' in targets:
config.unsupported = True
Other platform-specific tests are those that depend on a specific feature
of a specific sub-architecture, for example only to Intel chips that support ``AVX2``.
For instance, ``test/CodeGen/X86/psubus.ll`` tests three sub-architecture
variants:
.. code-block:: llvm
; RUN: llc -mcpu=core2 < %s | FileCheck %s -check-prefix=SSE2
; RUN: llc -mcpu=corei7-avx < %s | FileCheck %s -check-prefix=AVX1
; RUN: llc -mcpu=core-avx2 < %s | FileCheck %s -check-prefix=AVX2
And the checks are different:
.. code-block:: llvm
; SSE2: @test1
; SSE2: psubusw LCPI0_0(%rip), %xmm0
; AVX1: @test1
; AVX1: vpsubusw LCPI0_0(%rip), %xmm0, %xmm0
; AVX2: @test1
; AVX2: vpsubusw LCPI0_0(%rip), %xmm0, %xmm0
So, if you're testing for a behaviour that you know is platform-specific or
depends on special features of sub-architectures, you must add the specific
triple, test with the specific FileCheck and put it into the specific
directory that will filter out all other architectures.
Variables and substitutions
---------------------------