regehr
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10 years ago
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on: Souper – A Superoptimizer for LLVM IR
I'm one of the Souper developers and can offer a few pointers that may be more helpful than the github repo. Here's a somewhat recent blog post showing things that Souper can do:
http://blog.regehr.org/archives/1252
Here's a talk I gave at the University of Washington last winter (before Souper did synthesis):
https://www.youtube.com/watch?v=Ux0YnVEaI6A
Recently we've been teaching Souper to use dataflow facts such as LLVM's known bits and demanded bits. Perhaps interestingly, Souper can also teach LLVM how to compute these facts more precisely:
http://lists.llvm.org/pipermail/llvm-dev/2015-September/089904.html
One really common question about Souper is "why operate on LLVM IR instead of instructions?" One of the main answers is "so that we can interact with dataflow analyses." This isn't something that previous superoptimizers have done. It seems to be working out really well.
regehr
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10 years ago
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on: Calling conventions are hard – fuzz them
regehr
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10 years ago
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on: Finger Binary
My kids enjoy finger binary since they only need to count to four in order to give me the finger.
regehr
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10 years ago
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on: LLVM for Grad Students
Sure :).
regehr
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10 years ago
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on: LLVM for Grad Students
Many people have observed the LLVM appears to move unusually quickly. This is good except when it's bad.
regehr
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10 years ago
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on: LLVM for Grad Students
Adrian might have mentioned an important drawback of using LLVM: active effort is required to keep up with it. Many an LLVM-based research project has gotten stuck on 2.9 or 3.2 at which point it starts becoming less and less relevant.
It's not that big of a deal, but active effort is required. The amount of effort depends on how many and which APIs your project uses; for a small/medium project perhaps a couple of hours every couple of weeks.
regehr
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10 years ago
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on: SL-1: The only fatal nuclear reactor accident in US history
regehr
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10 years ago
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on: As Beijing Becomes a Supercity, the Rapid Growth Brings Pains
Sean, when I visited in 2012 I don't remember any security lines, is this new?
I found the Beijing subway to be far nicer than the ones found in major American cities. No surprise since it's much newer.
regehr
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10 years ago
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on: Lost Highways: Old roads in Vermont
One of my favorite things is an old highway in Kansas that emerges from a reservoir that was created in the 1960s and then drops back into the water a short distance away. It's in an out-of-the-way location and we used to go sit on the pavement and drink beer when I was in high school.
regehr
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11 years ago
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on: What afl-fuzz is bad at
The "without requiring you to think too much about the problem space" is pretty huge and it is where solver-based testing currently falls over (in my experience).
regehr
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11 years ago
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on: What If Students Could Fire Their Professors?
regehr
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11 years ago
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on: Why don’t our brains explode at movie cuts?
Watching TV/movies is definitely something that we learn to do, though most of us learned so early that we no longer remember it.
Source: anecdotal evidence from friends/relatives who observed childrens' reactions when first exposed to TV/movies when they were relatively old.
regehr
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11 years ago
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on: Why don’t our brains explode at movie cuts?
Often, the sound from the scene following the cut precedes the cut itself. There must be a name for this technique and a reason for it-- anyone know?
regehr
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11 years ago
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on: A short history of image manipulation before Photoshop
regehr
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11 years ago
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on: It’s Comcastic, Or: I Accidentally Bought a House Without Cable
512 kbps DSL -- just barely, frustratingly capable of watching Netflix at the worst quality level
regehr
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11 years ago
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on: It’s Comcastic, Or: I Accidentally Bought a House Without Cable
I bought a house about 1 mile from downtown Salt Lake City in 2008 and it took until last year to get a decent internet connection (from Comcast). First world problems!
regehr
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11 years ago
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on: Why Is Academic Writing So Academic?
regehr
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11 years ago
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on: A Career in Science Will Cost You Your Firstborn
I routinely forego summer salary in order to make sure the students are fed. This works because I receive a perfectly adequate 9-month salary from the state (and also my household has two incomes).
regehr
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11 years ago
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on: Automated Reasoning About LLVM Optimizations and Undefined Behavior
regehr
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11 years ago
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on: Proposal for a Friendly Dialect of C
