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lifted comparison codegen can be improved #17261

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lifted comparison codegen can be improved#17261
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Area-CompilersArea-PerformanceBugLanguage-C#good first issueThe issue is reserved for a first time, non-Microsoft contributorhelp wantedThe issue is "up for grabs" - add a comment if you are interested in working on it
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@VSadov

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@VSadov
VSadov
opened on Feb 20, 2017

In the codegen of lifted comparison operators some conditional branches seem unnecessary.
They only serve to shortcircuit trivial bool operators over locals - that does not seem very profitable.

We should do something like in: dotnet/corefx#15941
( Also check dotnet/corefx#17535 if that is better )

Example:

We emit lifted equality for left and right as:

bool? result = (left.GetValueOrDefault() == right.GetValueOrDefault()) ?
                                                  ( left.HasValue == right.HasValue ) :
                                                   false;

A more efficient would be:

bool? result = (left.GetValueOrDefault() == right.GetValueOrDefault()) & 
                                           (left.HasValue == right.HasValue);

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    Area-CompilersArea-PerformanceBugLanguage-C#good first issueThe issue is reserved for a first time, non-Microsoft contributorhelp wantedThe issue is "up for grabs" - add a comment if you are interested in working on it

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