i128 and u128 support
Brings i128 and u128 support to nightly rust, behind a feature flag. The goal of this PR is to do the bulk of the work for 128 bit integer support. Smaller but just as tricky features needed for stabilisation like 128 bit enum discriminants are left for future PRs.
Rebased version of #37900, which in turn was a rebase + improvement of #35954 . Sadly I couldn't reopen#37900 due to github. There goes my premium position in the homu queue...
[plugin-breaking-change]
cc #35118 (tracking issue)
There was a linker error on 32 bit platforms with optimisations turned off,
complaining that there was an undefined reference to "rust_eh_personality",
when compiling the rustc_const_math as stage1 artifact.
Apparently the compiler_builtins crate includes a call to "rust_eh_personality".
If compiled for 64 bits, this call doesn't appear, which explains why the linker
error only happens on 32 bit platforms, and optimisations will get it removed
on 32 bit as well.
There were two origins of the call:
1. A for loop where apparently the compiler wasn't sure
whether next() could panic or not, and therefore generated a landing
pad for the worst case. The minimal reproducible example is "for _ in 0..sr { }".
2. A default impl of uabs where the compiler apparently wasn't sure either
whether iabs() could panic or not. Many thanks to nagisa for
contributing the fix.
This commit also puts extern "C" to the intrinsics, as this is generally a
good thing to do.
* shift so that no panics are generated (otherwise results in linker error)
* no_std as insurance to not get into issues with errors like "cannot satisfy dependencies so `rustc_i128` only shows up once" (pure guessing here, but it doesn't hurt...)
The check inside compiler-rt file int_types.h to #define CRT_HAS_128BIT
looks like:
#if (defined(__LP64__) || defined(__wasm__)) && \
!(defined(__mips__) && defined(__clang__))
#define CRT_HAS_128BIT
#endif
Windows uses LLP64 instead of LP64, so it doesn't ship with the C based
intrinsics.
Also, add libcompiler_builtins to the list of crates that may have platform
specific checks (like the ones we just added).
Fix rustbuild on 32 bit Linux
This is cherry-picked from #37817 which seems to be stalled and currently needs to be rebased anyway.
r? @alexcrichton (who authored this change)
When compiling compiler-rt you typically compile with `-fvisibility=hidden`
which to ensure that all symbols are hidden in shared objects and don't show up
in symbol tables. This is important for these intrinsics being linked in every
crate to ensure that we're not unnecessarily bloating the public ABI of Rust
crates.
This should help allow the compiler-builtins project with Rust-defined builtins
start landing in-tree as well.
libcompiler-rt.a is dead, long live libcompiler-builtins.rlib
This commit moves the logic that used to build libcompiler-rt.a into a
compiler-builtins crate on top of the core crate and below the std crate.
This new crate still compiles the compiler-rt instrinsics using gcc-rs
but produces an .rlib instead of a static library.
Also, with this commit rustc no longer passes -lcompiler-rt to the
linker. This effectively makes the "no-compiler-rt" field of target
specifications a no-op. Users of `no_std` will have to explicitly add
the compiler-builtins crate to their crate dependency graph *if* they
need the compiler-rt intrinsics. Users of the `std` have to do nothing
extra as the std crate depends on compiler-builtins.
Finally, this a step towards lazy compilation of std with Cargo as the
compiler-rt intrinsics can now be built by Cargo instead of having to
be supplied by the user by some other method.
closes#34400
