[LLVMdev] major dragonegg improvement

Andrew Trick atrick at apple.com
Tue Sep 6 12:30:28 PDT 2011

Try -mllvm -disable-unroll-scev if you're curious.

There can be some luck involved. If you have the bitcode for the important function, I may be able to convert it into a test case to avoid regressing. I usually grab the unoptimized bitcode as follows: -emit-llvm -mllvm -disable-llvm-optzns -o module.bc


On Sep 6, 2011, at 12:03 PM, Owen Anderson wrote:

> Seems very likely to be related to Andy's SCEV-unroll-loops changes.
> --Owen
> On Sep 6, 2011, at 11:56 AM, Jack Howarth wrote:
>> I'm not certain yet which commit in the last couple of days caused this,
>> but the current llvm/dragonegg svn shows a major improvement in the runtime
>> of the xplor-nih testsuite when xplor-nih is built with FSF gcc 4.6.1 and the
>> dragonegg plugin at -O3 -ffast-math -funroll-loops. Previously the xplor-nih
>> testsuite always executed in ~40 sec but now it is coming it at 34.5 sec which
>> is about the same result seen for xplor-nih built with  native FSF gcc 4.6.1.
>> It will be interesting to find out if the Polyhedron 2005 benchmarks shows this
>> behavior as well. Nice.
>>             Jack
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