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POPL 2021
Sun 17 - Fri 22 January 2021 Online
Wed 20 Jan 2021 19:00 - 19:10 at POPL-A - Program Analysis

Vectorizing compilers employ divergence analysis to detect at which program point a specific variable is uniform, i.e. has the same value on all SIMD threads that execute this program point. They exploit uniformity to retain branching to counter branch divergence and defer computations to scalar processor units.

Divergence is a hyper-property and closely related to non-interference and binding time. There exist several divergence, binding time, and non-interference analyses already but they either sacrifice precision or make significant restrictions to the syntactical structure of the program in order to achieve soundness.

In this paper, we present the first abstract interpretation for uniformity that is general enough to be applicable to reducible CFGs and, at the same time, more precise than other analyses that achieve at least the same generality.

Our analysis comes with a correctness proof that is to a large part mechanized in Coq. Our experimental evaluation shows that the compile time and the precision of our analysis is on par with LLVM’s default divergence analysis that is only sound on more restricted CFGs. At the same time, our analysis is faster, achieves better precision and therefore enables faster vectorized programs, than a state-of-the-art non-interference analysis that is sound at least as general as our analysis.

Wed 20 Jan

Displayed time zone: Amsterdam, Berlin, Bern, Rome, Stockholm, Vienna change

18:30 - 19:30
Program AnalysisPOPL at POPL-A
18:30
10m
Talk
Verifying Correct Usage of Context-Free API Protocols
POPL
Kostas Ferles UT Austin, Jon Stephens University of Texas at Austin, Isil Dillig University of Texas at Austin
Link to publication DOI
18:40
10m
Talk
Data Flow Refinement Type Inference
POPL
Zvonimir Pavlinovic Google, USA, Yusen Su New York University, University of Waterloo, Thomas Wies New York University, USA
Link to publication DOI
18:50
10m
Talk
An Approach to Generate Correctly Rounded Math Libraries for New Floating Point Variants
POPL
Jay P. Lim Rutgers University, USA, Mridul Aanjaneya Rutgers University, John Gustafson National University of Singapore, Santosh Nagarakatte Rutgers University, USA
Link to publication DOI
19:00
10m
Talk
An Abstract Interpretation for SPMD Divergence on Reducible Control Flow GraphsDistinguished Paper
POPL
Julian Rosemann Saarland University, Saarland Informatics Campus, Simon Moll NEC Deutschland, Sebastian Hack Saarland University, Germany
Link to publication DOI
19:10
10m
Talk
Relatively Complete Verification of Probabilistic Programs
POPL
Kevin Batz RWTH Aachen University, Benjamin Lucien Kaminski RWTH Aachen University, Germany, Joost-Pieter Katoen RWTH Aachen University, Christoph Matheja ETH Zurich
Link to publication DOI
19:20
10m
Talk
A Practical Mode System for Recursive Definitions
POPL
Alban Reynaud ENS Lyon, Gabriel Scherer INRIA Saclay, Jeremy Yallop University of Cambridge
Link to publication DOI Pre-print