Also added FIXME comments to note the possible need to accommodate
counter increment calls in source-based functions that differ from the
function context of the caller instance (e.g., inline functions).

The mod uses both MIR bodies and HIR bodies, so I'm trying to maintain
consistency with these names.

This commit adds a query that allows the CoverageData to be pulled from
a call on tcx, avoiding the need to change the
`codegen_intrinsic_call()` signature (no need to pass in the FunctionCx
or any additional arguments.

The commit does not change where/when the CoverageData is computed. It's
still done in the `pass`, and saved in the MIR `Body`.

See discussion (in progress) here:
https://github.com/rust-lang/rust/pull/73488#discussion_r443825646

Replaced dummy values for hash and num_counters with computed values,
and refactored InstrumentCoverage pass to simplify injecting more
counters per function in upcoming versions.

Improved usage documentation and error messaging.

update from origin 2020-06-19

Rollup of 10 pull requests

Successful merges:

 - #72280 (Fix up autoderef when reborrowing)
 - #72785 (linker: MSVC supports linking static libraries as a whole archive)
 - #73011 (first stage of implementing LLVM code coverage)
 - #73044 (compiletest: Add directives to detect sanitizer support)
 - #73054 (memory access sanity checks: abort instead of panic)
 - #73136 (Change how compiler-builtins gets many CGUs)
 - #73280 (Add E0763)
 - #73317 (bootstrap: read config from $RUST_BOOTSTRAP_CONFIG)
 - #73350 (bootstrap/install.rs: support a nonexistent `prefix` in `x.py install`)
 - #73352 (Speed up bootstrap a little.)

Failed merges:

r? @ghost

Speed up bootstrap a little.

The bootstrap script was calling `cargo metadata` 3 times (or 6 with `-v`). This is a very expensive operation, and this attempts to avoid the extra calls. On my system, a simple command like `./x.py test -h -v` goes from about 3 seconds to 0.4.

An overview of the changes:

- Call `cargo metadata` only once with `--no-deps`. Optional dependencies are filtered in `in_tree_crates` (handling `profiler_builtins` and `rustc_codegen_llvm` which are driven by the config).
- Remove a duplicate call to `metadata::build` when using `-v`. I'm not sure why it was there, it looks like a mistake or vestigial from previous behavior.
- Remove check for `_shim`, I believe all the `_shim` crates are now gone.
- Remove check for `rustc_` and `*san` for `test::Crate::should_run`, these are no longer dependencies in the `test` tree.
- Use relative paths in `./x.py test -h -v` output.
- Some code cleanup (remove unnecessary `find_compiler_crates`, etc.).
- Show suite paths (`src/test/ui/...`) in `./x.py test -h -v` output.
- Some doc comments.

bootstrap/install.rs: support a nonexistent `prefix` in `x.py install`

PR #49778 introduced fs::canonicalize() which fails for a nonexistent path.
This is a surprise for someone used to GNU Autotools' configure which can create any necessary intermediate directories in prefix.

This change makes it run fs::create_dir_all() before canonicalize().

bootstrap: read config from $RUST_BOOTSTRAP_CONFIG

This PR modifies bootstrap so that `config.toml` is read first from `RUST_BOOTSTRAP_CONFIG`, then `--config` and finally `config.toml` in the current directory.

This is a subjective change, intended to improve the ergnomics when using "development shells" for rustc development (for example, using tools such as Nix) which set environment variables to ensure a reproducible environment (these development shells can then be version controlled, e.g. [my rustc shell](https://github.com/davidtwco/veritas/blob/6b74a5c170b6efb2c7b094352932f9158f97eec0/nix/shells/rustc.nix)). By optionally reading `config.toml` from an environment variable, a `config.toml` can be defined in the development shell and a path to it exposed in the `RUST_BOOTSTRAP_CONFIG` environment variable - avoiding the need to manually symlink the contents of this file to `config.toml` in the working directory.

Add E0763

Change how compiler-builtins gets many CGUs

This commit intends to fix an accidental regression from #70846. The
goal of #70846 was to build compiler-builtins with a maximal number of
CGUs to ensure that each module in the source corresponds to an object
file. This high degree of control for compiler-builtins is desirable to
ensure that there's at most one exported symbol per CGU, ideally
enabling compiler-builtins to not conflict with the system libgcc as
often.

In #70846, however, only part of the compiler understands that
compiler-builtins is built with many CGUs. The rest of the compiler
thinks it's building with `sess.codegen_units()`. Notably the
calculation of `sess.lto()` consults `sess.codegen_units()`, which when
there's only one CGU it disables ThinLTO. This means that
compiler-builtins is built without ThinLTO, which is quite harmful to
performance! This is the root of the cause from #73135 where intrinsics
were found to not be inlining trivial functions.

The fix applied in this commit is to remove the special-casing of
compiler-builtins in the compiler. Instead the build system is now
responsible for special-casing compiler-builtins. It doesn't know
exactly how many CGUs will be needed but it passes a large number that
is assumed to be much greater than the number of source-level modules
needed. After reading the various locations in the compiler source, this
seemed like the best solution rather than adding more and more special
casing in the compiler for compiler-builtins.

Closes #73135

memory access sanity checks: abort instead of panic

Suggested by @Mark-Simulacrum, this should help reduce the performance impact of these checks.

compiletest: Add directives to detect sanitizer support

Add needs-sanitizer-{address,leak,memory,thread} directive indicating
that test requires target with support for specific sanitizer.

This is an addition to the existing needs-sanitizer-support directive
indicating that test requires a sanitizer runtime library.

The existing needs-sanitizer-support directive could be incorporated into the
new ones, but I decided to retain it, since it enables running sanitizer
codegen tests even when building of sanitizer runtime libraries is disabled.

first stage of implementing LLVM code coverage

This PR replaces #70680 (WIP toward LLVM Code Coverage for Rust) since I am re-implementing the Rust LLVM code coverage feature in a different part of the compiler (in MIR pass(es) vs AST).

This PR updates rustc with `-Zinstrument-coverage` option that injects the llvm intrinsic `instrprof.increment()` for code generation.

This initial version only injects counters at the top of each function, and does not yet implement the required coverage map.

Upcoming PRs will add the coverage map, and add more counters and/or counter expressions for each conditional code branch.

Rust compiler MCP https://github.com/rust-lang/compiler-team/issues/278
Relevant issue: #34701 - Implement support for LLVMs code coverage instrumentation

***[I put together some development notes here, under a separate branch.](https://github.com/richkadel/rust/blob/cfa0b21d34ee64e4ebee226101bd2ef0c6757865/src/test/codegen/coverage-experiments/README-THIS-IS-TEMPORARY.md)***

linker: MSVC supports linking static libraries as a whole archive

Fix up autoderef when reborrowing

Currently `(f)()` and `f.call_mut()` behaves differently if expression `f` contains autoderef in it. This causes a weird error in #72225.

When `f` is type checked, `Deref` is used (this is expected as we can't yet determine if we should use `Fn` or `FnMut`). When subsequently we determine the actual trait to be used, when using the `f.call_mut()` syntax the `Deref` is patched to `DerefMut`, while for the `(f)()` syntax case it is not.

This PR replicates the fixup for the first case.

Fixes #72225
Fixes #68590

Rollup of 13 pull requests

Successful merges:

 - #70740 (Enabling static-pie for musl)
 - #72331 (Report error when casting an C-like enum implementing Drop)
 - #72486 (Fix asinh of negative values)
 - #72497 (tag/niche terminology cleanup)
 - #72999 (Create self-contained directory and move there some of external binaries/libs)
 - #73130 (Remove const prop for indirects)
 - #73142 (Ensure std benchmarks get tested.)
 - #73305 (Disallow loading crates with non-ascii identifier name.)
 - #73346 (Add rust specific features to print target features)
 - #73362 (Test that bounds checks are elided when slice len is checked up-front)
 - #73459 (Reduce pointer casts in Box::into_boxed_slice)
 - #73464 (Document format correction)
 - #73479 (Minor tweaks to liballoc)

Failed merges:

r? @ghost

Minor tweaks to liballoc

Document format correction

Minor amendments to the document.

r? @steveklabnik

Reduce pointer casts in Box::into_boxed_slice

We only need to cast the pointer once to change `Box<T>` to an array
`Box<[T; 1]>`, then we can let unsized coercion return `Box<[T]>`.

Test that bounds checks are elided when slice len is checked up-front

Closes #69101

Add rust specific features to print target features

Fixes #71583

`crt-static` is a rust specific target feature that's absent from llvm feature table, adding it there so that it shows under `rustc --print target-features`.

Probably the most native implementation I could think of, would love to get feedback.

Disallow loading crates with non-ascii identifier name.

This turns off external crate loading with non-ascii identifier names.

cc #55467.

Ensure std benchmarks get tested.

This ensures that the std benchmarks don't break in the future. Currently they aren't compiled or tested on CI, so they can easily bitrot.  Testing a benchmark runs it with one iteration. Adding these should only add a few seconds to CI.

Closes #54176
Closes #61913

Remove const prop for indirects

This was only used by one mir-opt test and since it causes buggy behavior under `-Zmir-opt-level=2`, it seems like we should remove it.

This was split out from #71946.

Closes #72679
Closes #72372
Closes #72285

Create self-contained directory and move there some of external binaries/libs

One of the steps to reach design described in https://github.com/rust-lang/rust/issues/68887#issuecomment-633048380
This PR moves things around and allows link code to handle the new directory structure.

tag/niche terminology cleanup

The term "discriminant" was used in two ways throughout the compiler:
* every enum variant has a corresponding discriminant, that can be given explicitly with `Variant = N`.
* that discriminant is then encoded in memory to store which variant is active -- but this encoded form of the discriminant was also often called "discriminant", even though it is conceptually quite different (e.g., it can be smaller in size, or even use niche-filling).

After discussion with @EddyB, this renames the second term to "tag". The way the tag is encoded can be either `TagEncoding::Direct` (formerly `DiscriminantKind::Tag`) or `TagEncoding::Niche` (formerly `DiscrimianntKind::Niche`).

This finally resolves some long-standing confusion I had about the handling of variant indices and discriminants, which surfaced in https://github.com/rust-lang/rust/pull/72419.

(There is also a `DiscriminantKind` type in libcore, it remains unaffected. I think this corresponds to the discriminant, not the tag, so that seems all right.)

r? @EddyB

Fix asinh of negative values

Rust's current implementation of asinh has [large errors](https://www.wolframalpha.com/input/?i=arcsinh%28x%29%2C+ln%28x%2B%28x%5E2%2B1%29%5E0.5%29%2C+x+from+-67452095.07139316+to+0) in its negative range. ~These are (mostly) not numerical, but rather seem due to an incorrect implementation.~ This appears to be due to avoidable catastrophic cancellation.
[Playground before/after](https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=bd04ae6d86d06612e4e389a8b95d19ab).
[glibc uses](https://github.com/bminor/glibc/blob/81dca813cc35f91414731fdd0ff6b756d5e1827f/sysdeps/ieee754/dbl-64/s_asinh.c#L56) abs here.

Many thanks to @danieldeankon for finding this weird behavior, @jebrosen for diagnosing it, and @toasteater for identifying the probable implementation error!

Report error when casting an C-like enum implementing Drop

Following approach described in https://github.com/rust-lang/rust/issues/35941

Enabling static-pie for musl

and make it the default for the x86_64-unknown-linux-musl target

This is a quick implementation for https://github.com/rust-lang/rust/issues/70693

Opening it as a draft PR to gather some feedback, before I put more work in it.

```console
❯ cat hello.rs
fn main() {
    println!("main = {:#x}", &main as *const _ as usize);
}

❯  /tmp/rust-musl/bin/rustc  --target x86_64-unknown-linux-musl  ~/hello.rs

❯ ldd hello
	statically linked

❯ file hello
hello: ELF 64-bit LSB shared object, x86-64, version 1 (GNU/Linux), statically linked, BuildID[sha1]=fec5cdc170f503a712a63a6958691ce5ce433654, with debug_info, not stripped

❯ ./hello
main = 0x7f233ca30008

❯ ./hello
main = 0x7f9ddc529008

❯ ./hello
main = 0x7f1e5a224008

❯ ./hello
main = 0x7f4485c7c008

❯ /tmp/rust-musl/bin/rustc  --target x86_64-unknown-linux-musl  -Z print-link-args  ~/hello.rs
"cc" "-Wl,--as-needed" "-Wl,-z,noexecstack" "-Wl,--eh-frame-hdr" "-m64" "-nostdlib" "/tmp/rust-musl/lib/rustlib/x86_64-unknown-linux-musl/lib/rcrt1.o" "/tmp/rust-musl/lib/rustlib/x86_64-unknown-linux-musl/lib/crti.o" "-L" "/tmp/rust-musl/lib/rustlib/x86_64-unknown-linux-musl/lib" "hello.hello.7rcbfp3g-cgu.0.rcgu.o" "hello.hello.7rcbfp3g-cgu.1.rcgu.o" "hello.hello.7rcbfp3g-cgu.2.rcgu.o" "hello.hello.7rcbfp3g-cgu.3.rcgu.o" "hello.hello.7rcbfp3g-cgu.4.rcgu.o" "hello.hello.7rcbfp3g-cgu.5.rcgu.o" "-o" "hello" "hello.1nxjf9so94czdgcz.rcgu.o" "-Wl,--gc-sections" "-static-pie" "-Wl,-zrelro" "-Wl,-znow" "-nodefaultlibs" "-L" "/tmp/rust-musl/lib/rustlib/x86_64-unknown-linux-musl/lib" "-Wl,--start-group" "-Wl,-Bstatic" "/tmp/rust-musl/lib/rustlib/x86_64-unknown-linux-musl/lib/libstd-0f9cb7646f9e2c34.rlib" "/tmp/rust-musl/lib/rustlib/x86_64-unknown-linux-musl/lib/libpanic_unwind-ba857f2f2e4e7187.rlib" "/tmp/rust-musl/lib/rustlib/x86_64-unknown-linux-musl/lib/libhashbrown-58ba5e25bbdf9d29.rlib" "/tmp/rust-musl/lib/rustlib/x86_64-unknown-linux-musl/lib/librustc_std_workspace_alloc-886bfe43afa847dc.rlib" "/tmp/rust-musl/lib/rustlib/x86_64-unknown-linux-musl/lib/libbacktrace-fbfb8fe99f19a67b.rlib" "/tmp/rust-musl/lib/rustlib/x86_64-unknown-linux-musl/lib/libbacktrace_sys-85fa859e7d364cc9.rlib" "/tmp/rust-musl/lib/rustlib/x86_64-unknown-linux-musl/lib/librustc_demangle-07ab026cd3ec0d82.rlib" "/tmp/rust-musl/lib/rustlib/x86_64-unknown-linux-musl/lib/libunwind-a8ec5932d92ea864.rlib" "/tmp/rust-musl/lib/rustlib/x86_64-unknown-linux-musl/lib/libcfg_if-0ba4cc2f38a198d5.rlib" "/tmp/rust-musl/lib/rustlib/x86_64-unknown-linux-musl/lib/liblibc-c1bb2b3ce4f78b7c.rlib" "/tmp/rust-musl/lib/rustlib/x86_64-unknown-linux-musl/lib/liballoc-0ff673c1cf0d451a.rlib" "/tmp/rust-musl/lib/rustlib/x86_64-unknown-linux-musl/lib/librustc_std_workspace_core-c8ff2001db856926.rlib" "/tmp/rust-musl/lib/rustlib/x86_64-unknown-linux-musl/lib/libcore-2ae14177140eeca2.rlib" "-Wl,--end-group" "/tmp/rust-musl/lib/rustlib/x86_64-unknown-linux-musl/lib/libcompiler_builtins-4fd81b5ce1b08a9c.rlib" "-static" "-Wl,-Bdynamic" "/tmp/rust-musl/lib/rustlib/x86_64-unknown-linux-musl/lib/crtn.o"
```

Closes https://github.com/rust-lang/rust/issues/70693
Closes https://github.com/rust-lang/rust/issues/53968

Rollup of 17 pull requests

Successful merges:

 - #70551 (Make all uses of ty::Error delay a span bug)
 - #71338 (Expand "recursive opaque type" diagnostic)
 - #71976 (Improve diagnostics for `let x += 1`)
 - #72279 (add raw_ref macros)
 - #72628 (Add tests for 'impl Default for [T; N]')
 - #72804 (Further tweak lifetime errors involving `dyn Trait` and `impl Trait` in return position)
 - #72814 (remove visit_terminator_kind from MIR visitor)
 - #72836 (Complete the std::time documentation to warn about the inconsistencies between OS)
 - #72968 (Only highlight doc search results via mouseover if mouse has moved)
 - #73034 (Export `#[inline]` fns with extern indicators)
 - #73315 (Clean up some weird command strings)
 - #73320 (Make new type param suggestion more targetted)
 - #73361 (Tweak "non-primitive cast" error)
 - #73425 (Mention functions pointers in the documentation)
 - #73428 (Fix typo in librustc_ast docs)
 - #73447 (Improve document for `Result::as_deref(_mut)` methods)
 - #73476 (Added tooltip for should_panic code examples)

Failed merges:

r? @ghost

update from origin 2020-06-18

Added tooltip for should_panic code examples

This change adds a tooltip to the documentation for `should_panic` examples. It currently displays identically to `compile_fail` examples, save for the changed text. It may be helpful to change the color that this displays in to make it visually more clear what is going on, but I'm unsure if additional colors wouldn't just be distracting.

I brought this [up on internals](https://internals.rust-lang.org/t/indicating-that-an-example-is-should-panic-in-docs/12544) a few days ago, and there seemed to be a mild positive response to it.

Improve document for `Result::as_deref(_mut)` methods

cc #50264

Fix typo in librustc_ast docs

Fixed sentence by removing a word.