[PATCH] D144316: [SCEV] Fix FoldID::addInteger(unsigned long I)

Mon Feb 20 04:51:29 PST 2023

fhahn added a comment.

In D144316#4137232 <https://reviews.llvm.org/D144316#4137232>, @nikic wrote:

> Looks like this had a fairly significant compile-time impact: https://llvm-compile-time-tracker.com/compare.php?from=c23f29d6f05b1fe4fa2dd50cbb78ee2b30e0de4d&to=a53d940cee6f281ef1a20d4f0fb39b23b4e98614&stat=instructions:u
>
> I think the current uses of FoldID will now have 5 elements and as such overflow SmallVector space, each resulting in a vector allocation?

Yeah looks like it. It looks like extending the size of the Bits vector should recover the regression while still retaining support for arbitrary SCEV expressions, which was the main reason for the current FoldID implementation.

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https://reviews.llvm.org/D144316