Add inline annotations and avoid 128-bit where it's not needed in TryFrom + tests for xsize/x128 #43194

oyvindln · 2017-07-12T20:54:03Z

This should make the output in #43064 slightly cleaner, and hopefully help fix #43124 when combined with #43127. I think the main issue was the lack of inline annotations for try_from (and not the use of 128-bit values as I first thought). Additionally, the implementations of try_from called min/max_value through the FromStrRadixHelper trait, which weren't marked inline either. I would have thought LLVM would be smart enough to inline this anyway, but it seems it isn't. While there has been talk about moving to a Cast trait for number types, it looks like it will take a while before that can happen, so this should help a bit in the meantime.

I didn't do any pointer width specific implementations for now.

This change also makes the assumption that i/usize is not larger than 64 bits wide to simplify things a little. Is that a safe assumption to make for now?

All the tests passed, but it's still possible I could have missed some parts.

This PR:
Avoids using i/u128 except for converting between 128-bit types.
Use the smallest type able to represent the maximum value instead for most types (except u/isize), and i/u64 otherwise.

Add sinline annotations to try_from implementations.
Before doing this the functions did not get inlined.

Avoids using the FromStrRadixHelper trait in the try_from implementations, as the trait wasn't actually needed for anything.

Add some simpler implementations for conversions that don't need as many checks. In release mode the checks will be optimized out when they're not needed anyhow, but this should at least result in very slightly less code non-optimized builds and very slightly less work for LLVM.

…From Avoid using i/u128 except for converting between 128-bit types. Use the smallest needed type instead for most types (except u/isize) Add inline annotations to try_from implementations. Before doing this the functions did not get inlined. Avoid using the FromStrRadixHelper trait in the try_from implementations. This wasn't needed for anything. Add some simpler implementations for conversions that don't need as many checks.

rust-highfive · 2017-07-12T20:54:08Z

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @aturon (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

aidanhs · 2017-07-13T00:30:42Z

Thanks for the PR @oyvindln, we'll check in now and again to make sure @aturon or another reviewer gets to this soon!

nagisa · 2017-07-13T12:53:07Z

src/libcore/num/mod.rs


+// The current implementations assume that usize/isize <= 64 bits wide.


This comment should be above over the trivial_try_from_impl!(usize, usize, u128, i128); rather than the whole block.

I would also recommend doing something like

#[cfg(not(any(target_pointer_width="16", ..., width="64")))] compile_error!("implementation assumes this and that")

Makes sense.

nagisa · 2017-07-13T12:54:10Z

src/libcore/num/mod.rs

+trivial_try_from_impl!(i64, i64, i128);
+trivial_try_from_impl!(i128, i128);
+trivial_try_from_impl!(isize, isize, i128);
+trivial_try_from_impl!(usize, u64);


Why separate from the trivial_try_from_impl!(usize, usize, u128, i128); above?

Ah, simply an oversight, you're right it should be together with the other unsigned ones.

nagisa · 2017-07-13T12:56:06Z

src/libcore/num/mod.rs

+same_sign_try_from_wider_impl!(u64, u128);
+same_sign_try_from_wider_impl!(i64, i128);
+
+// Need to make sure the storage component is large enough for these.


Ditto wrt comment. Use a compile_error! to verify your assumptions.

nagisa · 2017-07-13T12:57:06Z

src/libcore/num/mod.rs

+
+// Need to make sure the storage component is large enough for these.
+// (storage, target, $(source))
+same_sign_try_from_int_impl!(u64, usize, u64, u32, u16);


These would be better off with a #[cfg] and trivial_try_from_impl or try_from_wider depending on what the value of target_pointer_width is.

I initially decided to leave that for later as it seemed a bit complex to fully test, but I suppose I can try to do it properly.

oyvindln · 2017-07-13T16:22:34Z

Thanks for the feedback. I will see if I can sort out the issues pointed out.

Moved u64-usize macro call to the logical place

oyvindln · 2017-07-13T20:42:40Z

Okay, I think I sorted the requested changes.

I'm a bit unsure about the "compile_error" macro call after checking for an unknown bit width. I didn't enable the compile_error feature, as that would require me to add it to lib.rs, and add a statement to ignore the warning about unused feature. Though, at least it won't compile if the condition is hit, even though it won't give the proper compile_error message.

I didn't manage to compile for the 16-bit target (I got an missing specification error for the msp430_none_elf target which I don't know how to solve.), so that part is untested still.

I also couldn't find any tests for the usize and u128 types for TryFrom. Maybe that's something that ought to be added.

SimonSapin · 2017-07-13T22:42:25Z

I didn't manage to compile for the 16-bit target (I got an missing specification error for the msp430_none_elf target which I don't know how to solve.), so that part is untested still.

(Perhaps #43099 has not reached stage 0 yet? Before rust-lang/rust-forge#80 the platform support page linked to https://github.com/pftbest/rust_on_msp/blob/master/msp430.json.)

oyvindln · 2017-07-13T22:50:32Z

Yup, that seems to be the issue. I'm trying to build with rustc set to the latest nightly (which does have msp430 support) in config.toml now.

EDIT: So I didn't manage to compile for msp430 using x.py directly, but I did manage to compile libcore with the changes in this commit for msp430 with xargo at least.

nagisa · 2017-07-14T11:22:35Z

#[cfg_attr(any(target_poin...), feature(compile_error))] should work for the conditional feature.

nagisa · 2017-07-14T16:28:53Z

@oyvindln do you want to add the conversion tests for usize & u128? If not, I’ll review it as is.

oyvindln · 2017-07-14T16:44:17Z

@nagisa You can review it as is for now. I can do another PR with the tests once this one is sorted.

nagisa · 2017-07-14T17:30:38Z

src/libcore/num/mod.rs

+same_sign_try_from_wider_impl!(u64, u128);
+same_sign_try_from_wider_impl!(i64, i128);
+same_sign_try_from_wider_impl!(usize, u128);
+same_sign_try_from_wider_impl!(isize, u128);


Shouldn’t this be isize, i128?

nagisa · 2017-07-14T17:35:44Z

src/libcore/num/mod.rs

+        trivial_try_from_impl!(isize, i32);
+        // x64 -> xsize
+        same_sign_try_from_wider_impl!(usize, u64);
+        same_sign_try_from_wider_impl!(isize, u64);


A cross-sign conversion again.

I think this code would be easier follow if it was only split into blocks for each target_pointer_width.

Something like:

#[cfg(target_pointer_width = "16")] { trivial_try_from_impl!(usize, u16, u32); trivial_try_from_impl!(isize, i16, i32); same_sign_try_from_wider_impl!(usize, u32, u64); same_sign_try_from_wider_impl!(isize, i32, i64); } // and so forth.

~~Also, I believe the argument order is swapped for same_sign_try_from_wider_impl here and in the block above?~~ Was looking at the wrong macro.

It make make it more readable yeah.

oyvindln · 2017-07-14T17:58:42Z

So I think I'm going to try to add tests as well in this PR, looks like it's easy to miss stuff otherwise.

…e readable Adds tests for the TryFrom impelemtatnions for xsize and x128 values together with the existing tests for this trait. Fix a few impls that had the wrong values, and add some that had been missed in the last commits. Make TryFrom impl macros match on "into/from" to make them a bit more readable, and group the arguments on the macros that use a storage value.

oyvindln · 2017-07-15T16:23:13Z

The last commit adds the missing tests, and hopefully fixes the issues from the last one.

I borrowed the idea of using from/into as a separator in the macros from the try_from crate. Hopefully that makes it a bit easier to follow.

Also there is a new PR #43248 that does something similar to this PR. The approach used there may be a bit cleaner.

nagisa · 2017-07-16T11:54:36Z

I’m personally fine with either approach (they both look fairly similar to me). @llogiq needs to at least add tests and the #[inline] annotations -- something your PR has and their doesn’t.

If you feel that their implementation is better, I would suggest @llogiq to simply take your tests and merge that.

/me shrugs

oyvindln · 2017-07-16T12:40:52Z

If you think this one is fine, feel free to review/merge.

llogiq · 2017-07-16T17:29:28Z

@oyvindln are you OK with me cherry-picking your PR?

oyvindln · 2017-07-16T17:37:09Z

@llogiq Yup, that's fine by me.

aturon · 2017-07-17T22:44:52Z

r? @nagisa

alexcrichton · 2017-07-20T18:39:24Z

ping r? @nagisa

carols10cents · 2017-07-24T15:30:54Z

ping @nagisa @rust-lang/libs, it seems like this is ready for rereview!

nagisa · 2017-07-24T16:55:01Z

See this.

oyvindln · 2017-07-24T16:57:13Z

I think #43248 will be used instead. (Though I can fix up this to add the modules and avoid storage types if you don't feel like waiting for the other PR to be finished.)

oyvindln · 2017-07-24T20:47:10Z

Looks like #43248 is ready now, so I'm closing this in favour of that.

rust-highfive assigned aturon Jul 12, 2017

oyvindln mentioned this pull request Jul 12, 2017

The new step_by is too much slow #43064

Closed

aidanhs added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 13, 2017

nagisa requested changes Jul 13, 2017

View reviewed changes

Add bit width specific impls, add check for unknown bit width +

a9097fd

Moved u64-usize macro call to the logical place

Enable compile error feature

95156e3

nagisa reviewed Jul 14, 2017

View reviewed changes

oyvindln changed the title ~~Add inline annotations and avoid 128-bit where it's not needed in TryFrom~~ Add inline annotations and avoid 128-bit where it's not needed in TryFrom + tests for xsize/x128 Jul 15, 2017

oyvindln mentioned this pull request Jul 15, 2017

improve the TryFrom implementations #43248

Merged

rust-highfive assigned nagisa and unassigned aturon Jul 17, 2017

SimonSapin mentioned this pull request Jul 24, 2017

Redesign the std::iter::Step trait, tweak related iterator impls for ranges #43127

Closed

oyvindln closed this Jul 24, 2017

oyvindln deleted the tryfrom_avoid_128 branch July 27, 2017 23:58

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Add inline annotations and avoid 128-bit where it's not needed in TryFrom + tests for xsize/x128 #43194

Add inline annotations and avoid 128-bit where it's not needed in TryFrom + tests for xsize/x128 #43194

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		// The current implementations assume that usize/isize <= 64 bits wide.

Add inline annotations and avoid 128-bit where it's not needed in TryFrom + tests for xsize/x128 #43194

Add inline annotations and avoid 128-bit where it's not needed in TryFrom + tests for xsize/x128 #43194

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