Bounds checking #12
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Bounds checking #12
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…into new-pipeline
…e propagating persistent refinements out
… it did more harm than good
… into bounds-checking
… to simplify Acond and Awhile
…e GVal on each variable The old approach wouldn't work for terms without free variables
…orm if and awhile if condition is known, and other small changes to bounds analysis
… front-end, generate assertions from beginning
…them in Language.hs and Prelude.hs Desugaring was already rather difficult, and this way we don't need to complicate it further
…esugaring (aka lowering)
By other passes, the first subexpression may be (re)moved, making the analysis unsound
The old syntax-oriented uniqueness check did not work after adding assertions to permute. The fusion & in-place updates pass also could not remove the copy, as the array was constructed in an alloc and not written to by any operation. The copy is now eliminated by the operation simplifier, which checks wheter an operation is a copy operation for all of its outputs, and the corresponding inputs are undef
This makes it more clear that the assertion is ran after the given term. This commit also adds documentation to explain these semantics.
…nd vec (un)pack in Exp simplifier
These are equivalent to Lt and GtEq with their arguments swapped. By removing these two constructors, we simplify the compiler. We also can better detect that two expressions are the same (via matchOpenExp).
Since they just restructure two tuples, I removed these constructors. We can better track and analyse the program by just using the tuple constructors (Pair and Nil). The Exp simplifier already tried to remove uses of IndexSlice and IndexFull. Now we just do that always, directly from the beginning.
It can be replaced by a regular Const. This simplifies any pass that operates on expressions, and we can still recognize the primitive constants if we ever need to do that
TODO: Handle all OperationAcc constructors, and more testing
…est to inspectCompiler, add type synonym for set of transformation type classes of backends.
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@VLNohai I implemented a simplified bounds analysis based on your implementation and experiments. The new implementation is more conservative, but should not be sound with overflows and dead code elimination. It is also shorter (as we should also consider the maintainability of Accelerate). For now I put the bounds checks behind a flag. I would like to enable them by default, but I first want to see what the performance impact of the bounds checks are. The simplified analysis can already eliminate the bounds checks from |
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Description
Adds bounds checks, and a simplified analysis to statically prove some (hopefully most) of them statically.
Motivation and context
Indexing outside the bounds of an array is a common cause of many problems. Furthermore, other operations like fold1 require that the input is non-empty, which we didn't check yet in the new pipeline
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