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Add support for ARM NEON targets.

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Initial support for ARM NEON on Cortex-A9 and A15 CPUs.  All but ~10 tests
pass, and all examples compile and run correctly.  Most of the examples
show a ~2x speedup on a single A15 core versus scalar code.

Current open issues/TODOs
- Code quality looks decent, but hasn't been carefully examined.  Known
  issues/opportunities for improvement include:
  - fp32 vector divide is done as a series of scalar divides rather than
    a vector divide (which I believe exists, but I may be mistaken.)
    This is particularly harmful to examples/rt, which only runs ~1.5x
    faster with ispc, likely due to long chains of scalar divides.
  - The compiler isn't generating a vmin.f32 for e.g. the final scalar
    min in reduce_min(); instead it's generating a compare and then a
    select instruction (and similarly elsewhere).
  - There are some additional FIXMEs in builtins/target-neon.ll that
    include both a few pieces of missing functionality (e.g. rounding
    doubles) as well as places that deserve attention for possible
    code quality improvements.

- Currently only the "cortex-a9" and "cortex-15" CPU targets are
  supported; LLVM supports many other ARM CPUs and ispc should provide
  access to all of the ones that have NEON support (and aren't too
  obscure.)

- ~5 of the reduce-* tests hit an assertion inside LLVM (unfortunately
   only when the compiler runs on an ARM host, though).

- The Windows build hasn't been tested (though I've tried to update
  ispc.vcxproj appropriately).  It may just work, but will more likely
  have various small issues.)

- Anything related to 64-bit ARM has seen no attention.
This commit is contained in:
Matt Pharr
2013-07-19 11:06:11 -07:00
parent b007bba59f
commit d7b0c5794e
22 changed files with 914 additions and 67 deletions
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15
ispc.vcxproj
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@@ -45,6 +45,8 @@
<ClCompile Include="$(Configuration)\gen-bitcode-generic-32-64bit.cpp" />
<ClCompile Include="$(Configuration)\gen-bitcode-generic-64-32bit.cpp" />
<ClCompile Include="$(Configuration)\gen-bitcode-generic-64-64bit.cpp" />
<ClCompile Include="$(Configuration)\gen-bitcode-neon-32bit.cpp" />
<ClCompile Include="$(Configuration)\gen-bitcode-neon-64bit.cpp" />
<ClCompile Include="$(Configuration)\gen-bitcode-sse2-32bit.cpp" />
<ClCompile Include="$(Configuration)\gen-bitcode-sse2-64bit.cpp" />
<ClCompile Include="$(Configuration)\gen-bitcode-sse2-x2-32bit.cpp" />
@@ -185,6 +187,19 @@
<Message>Building gen-bitcode-sse2-x2-64bit.cpp</Message>
</CustomBuild>
</ItemGroup>
<ItemGroup>
<CustomBuild Include="builtins\target-neon.ll">
<FileType>Document</FileType>
<Command Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">m4 -Ibuiltins/ -DLLVM_VERSION=%LLVM_VERSION% builtins\target-neon.ll | python bitcode2cpp.py builtins\target-neon.ll &gt; gen-bitcode-neon.cpp</Command>
<Outputs Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">gen-bitcode-neon.cpp</Outputs>
<AdditionalInputs Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">builtins\util.m4</AdditionalInputs>
<Command Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">m4 -Ibuiltins/ -DLLVM_VERSION=%LLVM_VERSION% builtins\target-neon.ll | python bitcode2cpp.py builtins\target-neon.ll &gt; gen-bitcode-neon.cpp</Command>
<Outputs Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">gen-bitcode-neon.cpp</Outputs>
<AdditionalInputs Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">builtins\util.m4</AdditionalInputs>
<Message Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">Building gen-bitcode-neon.cpp</Message>
<Message Condition="'$(Configuration)|$(Platform)'=='Release|Win32'">Building gen-bitcode-neon.cpp</Message>
</CustomBuild>
</ItemGroup>
<ItemGroup>
<CustomBuild Include="builtins\target-avx1.ll">
<FileType>Document</FileType>