[EXTERNAL] Re: [PATCH][WIP] PR tree-optimization/101808 Boolean comparison simplification

Jeff Law jeffreyalaw@gmail.com
Tue Nov 23 20:14:30 GMT 2021

On 11/23/2021 1:08 PM, Navid Rahimi wrote:
>> In gimple your primary goal should be to reduce the number of
>> expressions that are evaluated.  This patch does the opposite.
> That is actually a really good point in my opinion. I am hesitant about this patch and wanted to hear gcc-patch opinion about this. Doing something like this in IR level is a little bit counter intuitive to me. I will take a look at LLVM in my spare time to see where they are transferring that pattern and what was the rationale behind it.
It could be easily looked at as target expansion issue.  ie, there's two 
equivalent forms for the full expression and the desired form varies 
based on some property of the target.  The idea we've kicked around, but 
not implemented, would be to allow target specific match.pd patterns to 
drive rewriting expressions at the gimple->rtl border.


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