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Matt Pharr
2011-12-01 17:00:41 -08:00
parent 24ef9dac8f
commit 511a3ab15a
2 changed files with 641 additions and 539 deletions
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docs/ispc.txt
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docs/perf.txt
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@@ -207,20 +207,9 @@ instances often do compute the same boolean value, this overhead is
worthwhile. If the control flow is in fact usually incoherent, this worthwhile. If the control flow is in fact usually incoherent, this
overhead only costs performance. overhead only costs performance.
In a similar fashion, ``ispc`` provides ``cfor``, ``cwhile``, ``cdo``, In a similar fashion, ``ispc`` provides ``cfor``, ``cwhile``, and ``cdo``
``cbreak``, ``ccontinue``, and ``creturn`` statements. These statements statements. These statements are semantically the same as the
are semantically the same as the corresponding non-"c"-prefixed functions. corresponding non-"c"-prefixed functions.
For example, when ``ispc`` encounters a regular ``continue`` statement in
the middle of loop, it disables the mask bits for the program instances
that executed the ``continue`` and then executes the remainder of the loop
body, under the expectation that other executing program instances will
still need to run those instructions. If you expect that all running
program instances will often execute ``continue`` together, then
``ccontinue`` provides the compiler a hint to do extra work to check if
every running program instance continued, in which case it can jump to the
end of the loop, saving the work of executing the otherwise meaningless
instructions.
Use "uniform" Whenever Appropriate Use "uniform" Whenever Appropriate
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