implement the write_bytes() intrinsic #148
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Travis is failing because the build is broken on the latest nightly.
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src/terminator/intrinsic.rs
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| let count = self.value_to_primval(arg_vals[2], usize)?.to_u64()?; | ||
| for _ in 0..count { | ||
| self.write_value_to_ptr(val_full, ptr, ty)?; |
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I don't think this is going to work properly for non-primitive types, especially when they are larger than u128.
I would rather eliminate all the pattern/val_full code and replace it with a simple loop with size * count iterations, writing a single val_byte each iteration.
Can you also add a test where ty is something like a struct with at least 3 fields (so our ByVal/ByValPair optimizations definitely won't take effect)?
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I would rather eliminate all the pattern/val_full code and replace it with a simple loop with size * count iterations, writing a single val_byte each iteration.
Actually, I think you could do a lower-level let bytes = self.memory.get_bytes_mut(ptr, size * count, ty_align); and then do a loop simply assigning the bytes directly. This would be much more efficient than repeatedly calling a single-byte write function on Memory which would do a lot of checks. It should be even more efficient than the val_full code.
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Memory::get_bytes_mut() is private and therefore inaccessible here. Shall I make it public?
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I've pushed a commit that updates to a simple loop with size * count iterations.
I shied away from using get_bytes_mut() for now.
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Ah, true. Just now when I was looking for a public wrapper, I noticed Memory::write_repeat which even does the loop for you.
The only thing I'm unsure about is the alignment requirement. write_repeat assumes no alignment requirement (align = 1), but I'm not sure if this write_bytes intrinsic should require the alignment of the type it's parameterized over.
Perhaps we could do:
self.memory.check_align(ptr, size * count, ty_align);
self.memory.write_repeat(ptr, val_byte, size * count);
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