Call::prefetch's return type indicates the type being prefetched, which does not match the implementation #4211
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steven-johnson
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Jun 8, 2023
As noted in the issue above, the return type of this Call was used weirdly and wrongly: it wasn't the return type of the intrinsic (which is always int32, and always ignored), but rather, the type of the elements to prefetch. This didn't seem to be causing any obvious errors, but it meant we needed some weird special cases in the code. We now insert another element in the args to carry the type needed (with a value of constant zero).
abadams
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Jun 12, 2023
Call::Prefetch evaluates to a currently-unspecified value of the prefetched type. Let's just make it zero.
steven-johnson
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Jun 17, 2023
* Alternative fix for #4211 Call::Prefetch evaluates to a currently-unspecified value of the prefetched type. Let's just make it zero. * Fix prefetch_2d * Fix CodeGen_C * Fix CodeGen_C * trigger buildbots --------- Co-authored-by: Steven Johnson <srj@google.com>
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ardier
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Mar 3, 2024
* Alternative fix for halide#4211 Call::Prefetch evaluates to a currently-unspecified value of the prefetched type. Let's just make it zero. * Fix prefetch_2d * Fix CodeGen_C * Fix CodeGen_C * trigger buildbots --------- Co-authored-by: Steven Johnson <srj@google.com>
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This change of #3667: https://github.com/halide/Halide/pull/3667/files#diff-a8d8ceb2b87d97fbb8fe6eea48d2178f broke prefetching. Apparently, the return type of
Call::prefetchindicates the type of prefetching to perform in some places, e.g.Halide/src/CodeGen_C.cpp
Line 2281 in 4b545dd
But not others, e.g.:
Halide/src/CodeGen_LLVM.cpp
Line 3054 in 4b545dd
It seems reasonable-ish for prefetch to be defined this way (it looks kind of like a load), but it is difficult to implement. If we want to keep this behavior, then I think we need to make a special case for this function in CodeGen_LLVM and CodeGen_Hexagon.
For now, I am going to send a PR to fix the breakage by adding an exception for
Call::prefetchto the new assert, but I'm going to leave this issue open because this seems like it needs improvement.The text was updated successfully, but these errors were encountered: