Accelerating Existing C Code Using TIE
One of the reasons for resorting to assembly language
use is because conventional, fixed-ISA processors
often cannot achieve performance goals using C
or C++ alone. However, even assembly code is limited
to the native performance of the fixed-ISA processor.
Tensilica’s Xtensa processor is extensible.
This extensibility allows the processor’s
resources and capabilities to be tailored to specific
tasks. Program optimization using TIE (Tensilica’s
Instruction Extension language for the Xtensa processor)
is first accomplished by identifying hot spots
in the C code – performance-sensitive regions
of application code usually residing in the inner
loops of algorithms. The execution
profiler allows
a system designer to quickly analyze code efficiency
and to identify where custom instructions (implemented
with TIE) can best enhance performance. The software
/firmware team or the system designer then defines
and implements one or more new TIE instructions
to accelerate the hot-spot code.
Stay in C, No Assembly Coding Required
The new TIE instructions appear as intrinsic function
calls in C-code routines. The need for assembly
coding disappears. Xtensa compilers automatically
perform all the necessary optimizations, register
allocations, and scheduling of the assembly code
generated by the compilation. To get more performance,
the system designer can rebuild the processor with
additional TIE instructions and re-profile the
application to see the performance gain.
The designer can iteratively develop a sequence
of processor builds while profiling each new tailored
processor to weigh the benefit of adding instructions
and pipeline-acceleration hardware through the
TIE language. Aggressive use of function-unit parallelism
and other acceleration techniques (such as overlapping
loads with instruction execution) can often deliver
10X, 100X, or even greater performance increases.
For general information on Xtensa software development
tools, click here
For more information on specific software development
tools available for the Xtensa processor, click
on the links below:
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