High-Throughput, Formal-Methods-Assisted Fuzzing for LLVM

[This piece is co-authored with Vsevolod Livinskii.] Formal verification isn’t some sort of magic pixie dust that we sprinkle over a computer system to make it better. Real formal verification involves a lot of the same kind of difficult, nasty, grungy engineering work that any other systems-level job involves. Furthermore, the verification tools...

Compilers can be improved over time, but this is a slow process. “Proebsting’s Law” is an old joke which suggested that advances in compiler optimization will double the speed of a computation every 18 years — but if anything this is optimistic. Slow compiler evolution is never a good thing, but this is particularly problematic […]

In its original form, a peephole optimization applied to a collection of instructions located close together in a program. For example, in a register transfer language we might find this sequence of instructions: r0 = xor r8, -1 r1 = xor r9, -1 r0 = and r0, r1 Here, assuming the two’s complement representation, -1 […]

[This piece is co-authored by Ryan Berger and Stefan Mada (both Utah CS undergrads), by Nader Boushehri, and by John Regehr.] An optimizing compiler traditionally has three main parts: a frontend that translates a source language into an intermediate representation (IR), a “middle end” that rewrites IR into better IR, and then a backend that […]

The spinlock is the most basic mutual exclusion primitive provided by a multiprocessor operating system. Spinlocks need to protect against preemption on the current CPU (typically by disabling interrupts, but we’ll ignore that aspect in this post) and also against attempts by other cores to concurrently access the critical section (by using...