trans: Make type names in LLVM IR independent of crate-nums and source locations.
UPDATE:
This PR makes the type names we assign in LLVM IR independent of the type definition's location in the source code and the order in which extern crates are loaded. The new type names look like the old ones, except for closures and the `<crate-num>.` prefix being gone. Resolution of name clashes (e.g. of the same type in different crate versions) is left to LLVM (which will just append `.<counter>` to the name).
ORIGINAL TEXT:
This PR makes the type names we assign in LLVM IR independent of the type definition's location in the source code. Before, the type of closures contained the closures definition location. The new naming scheme follows the same pattern that we already use for symbol names: We have a human readable prefix followed by a hash that makes sure we don't have any collisions. Here is an example of what the new names look like:
```rust
// prog.rs - example program
mod mod1
{
pub struct Struct<T>(pub T);
}
fn main() {
use mod1::Struct;
let _s = Struct(0u32);
let _t = Struct('h');
let _x = Struct(Struct(0i32));
}
```
Old:
```llvm
%"mod1::Struct<u32>" = type { i32 }
%"mod1::Struct<char>" = type { i32 }
%"mod1::Struct<mod1::Struct<i32>>" = type { %"mod1::Struct<i32>" }
%"mod1::Struct<i32>" = type { i32 }
```
New:
```llvm
%"prog::mod1::Struct<u32>::ejDrT" = type { i32 }
%"prog::mod1::Struct<char>::2eEAU" = type { i32 }
%"prog::mod1::Struct<prog::mod1::Struct<i32>>::ehCqR" = type { %"prog::mod1::Struct<i32>::$fAo2" }
%"prog::mod1::Struct<i32>::$fAo2" = type { i32 }
```
As you can see, the new names are slightly more verbose, but also more consistent. There is no difference now between a local type and one from another crate (before, non-local types where prefixed with `<crate-num>.` as in `2.std::mod1::Type1`).
There is a bit of design space here. For example, we could leave off the crate name for local definitions (making names shorter but less consistent):
```llvm
%"mod1::Struct<u32>::ejDrT" = type { i32 }
%"mod1::Struct<char>::2eEAU" = type { i32 }
%"mod1::Struct<mod1::Struct<i32>>::ehCqR" = type { %"mod1::Struct<i32>::$fAo2" }
%"mod1::Struct<i32>::$fAo2" = type { i32 }
```
We could also put the hash in front, which might be more readable:
```llvm
%"ejDrT.mod1::Struct<u32>" = type { i32 }
%"2eEAU.mod1::Struct<char>" = type { i32 }
%"ehCqR.mod1::Struct<mod1::Struct<i32>>" = type { %"$fAo2.mod1::Struct<i32>" }
%"$fAo2.mod1::Struct<i32>" = type { i32 }
```
We could probably also get rid of the hash if we used full DefPaths and crate-nums (though I'm not yet a 100% sure if crate-nums could mess with incremental compilation).
```llvm
%"mod1::Struct<u32>" = type { i32 }
%"mod1::Struct<char>" = type { i32 }
%"mod1::Struct<mod1::Struct<i32>>" = type { %"mod1::Struct<i32>" }
%"mod1::Struct<i32>" = type { i32 }
%"2.std::mod1::Type1" = type { ... }
```
I would prefer the solution with the hashes because it is nice and consistent conceptually, but visually it's admittedly a bit uglier. Maybe @rust-lang/compiler would like to bikeshed a little about this.
On a related note: Has anyone ever tried if the LTO-linker will merge equal types with different names?
(^ @brson, @alexcrichton ^)
If not, that would be a reason to make type names more consistent.
Before this PR, type names could depend on the cratenum being used
for a given crate and also on the source location of closures.
Both are undesirable for incremental compilation where we cache
LLVM IR and don't want it to depend on formatting or in which
order crates are loaded.
Macro parser performance improvements and refactoring
This PR locally increased performance of https://github.com/rust-lang/rust/issues/37074 by ~6.6 minutes.
Follow up to https://github.com/rust-lang/rust/pull/37569, but doesn't focus explicitly on expansion performance.
History is relatively clean, but I can/will do some more polishing if this is deemed mergeable. Partially posting this now so I can get Travis to run tests for me.
r? @jseyfried
Translate closures through the collector
Now that old trans is gone, there is no need for the hack of translating closures when they are instantiated. We can translate them like regular items.
r? @eddyb
compile-test: allow overriding nodejs binary location
Add a command-line argument to manually specify which nodejs binary should be used,
which disables the default search.
Original work done by @tari.
Fixes#34188.
vec: Write the .extend() specialization in cleaner style
As far as possible, use regular `default fn` specialization in favour of
ad-hoc conditionals.
No intentional functional change. Code quality was validated against the same
benchmarks that were used in initial trusted len development.
This change is prompted by taking impressions from
https://github.com/rust-lang/rust/issues/27749#issuecomment-244498705
change the `box_free` lang item to accept pointers to unsized types
in miri we use the `box_free` lang item as the destructor for `Box` objects, since the function's api matches that of an `fn drop(&mut self)` in a hypothetical `impl<T: ?Sized> Drop for Box<T>` exactly.
This works fine except if we insert a check in the `size_of` intrinsic to ensure that it is only called with sized types, since the `box_free` lang item calls that intrinsic.
cc @eddyb
no clue who to r? here, probably lang team?
Avoid unnecessary mk_ty calls in Ty::super_fold_with.
This speeds up compilation of several rustc-benchmarks by 1--2% and the workload in #36799 by 5%.
r? @eddyb
std: Derive `Default` for `Duration`.
Discussed in #37546 the libs team reached the conclusion that a default zero
duration seems like a reasonable implementation of the `Default` trait.
Closes#37546
Remove one bounds check from BufReader
Very minor thing. Otherwise the optimizer can't be sure that pos <= cap. Added a paranoid debug_assert to ensure correctness instead.
CC #37573
On fmt string with unescaped `{` note how to escape
On cases of malformed format strings where a `{` hasn't been properly escaped, like `println!("{");`, present a NOTE explaining how to escape the `{` char.
Fix#34300.
