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change documentation to remove llvm-3.2 dependency

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evghenii
2014-07-08 15:25:22 +02:00
parent c117c49dc9
commit 8894156df5
1 changed files with 18 additions and 17 deletions
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docs/ispc.rst
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@@ -4954,7 +4954,7 @@ Overview
-------- --------
SPMD programming in ``ispc`` is similar to a warp-synchronous CUDA programming. SPMD programming in ``ispc`` is similar to a warp-synchronous CUDA programming.
Namely, program instances in a gang are equivalent of CUDA threads in a single Namely, program instances in a gang are equivalent of CUDA threads in a single
warp. Hence, to run efficiently on a GPU `ispc`` program must use tasking warp. Hence, to run efficiently on a GPU ``ispc`` program must use tasking
functionality via ``launch`` keyword to ensure multiple number of warps are functionality via ``launch`` keyword to ensure multiple number of warps are
executed concurrently on the GPU. executed concurrently on the GPU.
@@ -4965,7 +4965,7 @@ utilize ``launch`` keyword to schedule work on a GPU.
At the PTX level, ``launch`` keyword is mapped to CUDA Dynamic Parallelism and At the PTX level, ``launch`` keyword is mapped to CUDA Dynamic Parallelism and
it schedules a grid of thread-blocks each 4 warps-wide (128 threads). As a it schedules a grid of thread-blocks each 4 warps-wide (128 threads). As a
result, `ispc`` has a tasking-granularity of 4 tasks with PTX target; this result, ``ispc`` has a tasking-granularity of 4 tasks with PTX target; this
restriction will be eliminated in future. restriction will be eliminated in future.
When passing pointers to an ``export`` function, it is important that they When passing pointers to an ``export`` function, it is important that they
@@ -4982,30 +4982,31 @@ Compiling For The NVIDIA Kepler GPU
----------------------------------- -----------------------------------
Compilation for NVIDIA Kepler GPU is a several step procedure. Compilation for NVIDIA Kepler GPU is a several step procedure.
First, we need to generate a LLVM bitcode from ``ispc`` source file: First, we need to generate a LLVM assembly from ``ispc`` source file (``ispc``
generates LLVM assembly instead of bitcode when ``nvptx`` target is chosen):
:: ::
$ISPC_HOME/ispc foo.ispc --emit-llvm --target=nvptx -o foo.bc $ISPC_HOME/ispc foo.ispc --emit-llvm --target=nvptx -o foo.ll
If ``ispc`` is compiled with LLVM 3.2, the resulting bitcode can immediately be
compiled into PTX with the help of ``ptxgen`` tool; this tool uses ``libNVVM`` This LLVM assembly can immediately be compiled into PTX with the help of
which is a part of a CUDA Toolkit. ``ptxgen`` tool; this tool uses ``libNVVM`` which is a part of a CUDA Toolkit.
:: ::
$ISPC_HOME/ptxtools/ptxgen --use_fast_math foo.bc -o foo.ptx
If ``ispc`` is compiled with LLVM >3.2, the resulting bitcode must first be
decompiled with the ``llvm-dis`` from LLVM 3.2 distribution; this "trick" is
required to generate an IR compatible with libNVVM:
::
$LLVM32/bin/llvm-dis foo.bc -o foo.ll
$ISPC_HOME/ptxtools/ptxgen --use_fast_math foo.ll -o foo.ptx $ISPC_HOME/ptxtools/ptxgen --use_fast_math foo.ll -o foo.ptx
The resulting PTX code is ready for execution on a GPU, for example via CUDA .. If ``ispc`` is compiled with LLVM >3.2, the resulting bitcode must first be
.. decompiled with the ``llvm-dis`` from LLVM 3.2 distribution; this "trick" is
.. required to generate an IR compatible with libNVVM:
.. ::
..
.. $LLVM32/bin/llvm-dis foo.bc -o foo.ll
.. $ISPC_HOME/ptxtools/ptxgen --use_fast_math foo.ll -o foo.ptx
This PTX is ready for execution on a GPU, for example via CUDA
Driver API. Alternatively, we also provide a simple ``ptxcc`` tool, which Driver API. Alternatively, we also provide a simple ``ptxcc`` tool, which
compiles the resulting PTX code into an object file: compiles the resulting PTX code into an object file: