[llvm-commits] [llvm] r131088 - in /llvm/trunk: include/llvm/Analysis/ScalarEvolution.h lib/Analysis/ScalarEvolution.cpp

[Dan Gohman]

On May 9, 2011, at 11:52 AM, Eli Friedman wrote:

> On Mon, May 9, 2011 at 11:44 AM, Dan Gohman <gohman at apple.com> wrote:
>> 
>>     /// BlockDispositions - Memoized computeBlockDisposition results.
>> -    std::map<const SCEV *,
>> +    DenseMap<const SCEV *,
>>              std::map<const BasicBlock *, BlockDisposition> > BlockDispositions;
> 
> Somehow a DenseMap of std::map doesn't strike me as good for
> performance; copying an std::map isn't cheap.


True, which I believe why this change wasn't made earlier.
But it also doesn't happen very often. I haven't seen slowdowns
in a variety of tests.

Dan