llvm/llvm-project

[Support] Investigate making KnownBits saturated add/sub implementations optimal

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#84,213 opened on Mar 6, 2024

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good first issuellvm:support

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Description

https://github.com/llvm/llvm-project/blob/44be5a7fdc20a7f90d63dc18699a470e900bd3ba/llvm/unittests/Support/KnownBitsTest.cpp#L429-L460

Investigate if we can make the implementation optimal (checkOptimalityBinary)

Contributor guide

Research direction
Examine the test code in KnownBitsTest.cpp to understand the current implementation's optimality checks. Then, review the KnownBits saturated add/sub implementations in KnownBits.h or related files to identify potential inefficiencies. Compare with known optimal algorithms for saturated arithmetic (e.g., using carry bits or min/max).
Tech stack
cpp
Domain
compilers
Issue type
Research
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C++Git
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70