Current `-Zinstrument-mcount` for ARM32 use the `\01__gnu_mcount_nc`
directly for its instrumentation function.

However, the LLVM does not use this mcount function directly, but it wraps
it to intrinsic, `llvm.arm.gnu.eabi.mcount` and the transform pass also
only handle the intrinsic.

As a result, current `-Zinstrument-mcount` not work on ARM32.
Refer: https://github.com/namhyung/uftrace/issues/1764

This commit replaces the mcount name from native function to the
LLVM intrinsic so that the transform pass can handle it.
Signed-off-by: NChoKyuWon <kyuwoncho18@gmail.com>

Co-authored-by: Nbjorn3 <17426603+bjorn3@users.noreply.github.com>

Similar to prior support added for the mips430, avr, and x86 targets
this change implements the rough equivalent of clang's
[`__attribute__((interrupt))`][clang-attr] for riscv targets, enabling
e.g.

```rust
static mut CNT: usize = 0;

pub extern "riscv-interrupt-m" fn isr_m() {
    unsafe {
        CNT += 1;
    }
}
```

to produce highly effective assembly like:

```asm
pub extern "riscv-interrupt-m" fn isr_m() {
420003a0:       1141                    addi    sp,sp,-16
    unsafe {
        CNT += 1;
420003a2:       c62a                    sw      a0,12(sp)
420003a4:       c42e                    sw      a1,8(sp)
420003a6:       3fc80537                lui     a0,0x3fc80
420003aa:       63c52583                lw      a1,1596(a0) # 3fc8063c <_ZN12esp_riscv_rt3CNT17hcec3e3a214887d53E.0>
420003ae:       0585                    addi    a1,a1,1
420003b0:       62b52e23                sw      a1,1596(a0)
    }
}
420003b4:       4532                    lw      a0,12(sp)
420003b6:       45a2                    lw      a1,8(sp)
420003b8:       0141                    addi    sp,sp,16
420003ba:       30200073                mret
```

(disassembly via `riscv64-unknown-elf-objdump -C -S --disassemble ./esp32c3-hal/target/riscv32imc-unknown-none-elf/release/examples/gpio_interrupt`)

This outcome is superior to hand-coded interrupt routines which, lacking
visibility into any non-assembly body of the interrupt handler, have to
be very conservative and save the [entire CPU state to the stack
frame][full-frame-save]. By instead asking LLVM to only save the
registers that it uses, we defer the decision to the tool with the best
context: it can more accurately account for the cost of spills if it
knows that every additional register used is already at the cost of an
implicit spill.

At the LLVM level, this is apparently [implemented by] marking every
register as "[callee-save]," matching the semantics of an interrupt
handler nicely (it has to leave the CPU state just as it found it after
its `{m|s}ret`).

This approach is not suitable for every interrupt handler, as it makes
no attempt to e.g. save the state in a user-accessible stack frame. For
a full discussion of those challenges and tradeoffs, please refer to
[the interrupt calling conventions RFC][rfc].

Inside rustc, this implementation differs from prior art because LLVM
does not expose the "all-saved" function flavor as a calling convention
directly, instead preferring to use an attribute that allows for
differentiating between "machine-mode" and "superivsor-mode" interrupts.

Finally, some effort has been made to guide those who may not yet be
aware of the differences between machine-mode and supervisor-mode
interrupts as to why no `riscv-interrupt` calling convention is exposed
through rustc, and similarly for why `riscv-interrupt-u` makes no
appearance (as it would complicate future LLVM upgrades).

[clang-attr]: https://clang.llvm.org/docs/AttributeReference.html#interrupt-risc-v
[full-frame-save]: https://github.com/esp-rs/esp-riscv-rt/blob/9281af2ecffe13e40992917316f36920c26acaf3/src/lib.rs#L440-L469
[implemented by]: https://github.com/llvm/llvm-project/blob/b7fb2a3fec7c187d58a6d338ab512d9173bca987/llvm/lib/Target/RISCV/RISCVRegisterInfo.cpp#L61-L67
[callee-save]: https://github.com/llvm/llvm-project/blob/973f1fe7a8591c7af148e573491ab68cc15b6ecf/llvm/lib/Target/RISCV/RISCVCallingConv.td#L30-L37
[rfc]: https://github.com/rust-lang/rfcs/pull/3246

Function pointer alignment is specified since https://reviews.llvm.org/D147016.

This reverts commit 90f0b24a, reversing
changes made to e173a8e6.

It lints against features that are inteded to be internal to the
compiler and standard library. Implements MCP #596.

We allow `internal_features` in the standard library and compiler as those
use many features and this _is_ the standard library from the "internal to the compiler and
standard library" after all.

Marking some features as internal wasn't exactly the most scientific approach, I just marked some
mostly obvious features. While there is a categorization in the macro,
it's not very well upheld (should probably be fixed in another PR).

We always pass `-Ainternal_features` in the testsuite
About 400 UI tests and several other tests use internal features.
Instead of throwing the attribute on each one, just always allow them.
There's nothing wrong with testing internal features^^

Signed-off-by: N袁浩 <yuanhao34@huawei.com>

Signed-off-by: NMartin Kröning <martin.kroening@eonerc.rwth-aachen.de>

Co-authored-by: NMartin Kröning <martin.kroening@eonerc.rwth-aachen.de>
Signed-off-by: NMartin Kröning <martin.kroening@eonerc.rwth-aachen.de>

instead of mutating the base.
Signed-off-by: NMartin Kröning <martin.kroening@eonerc.rwth-aachen.de>

Signed-off-by: NMartin Kröning <martin.kroening@eonerc.rwth-aachen.de>

These pre-link args are remains from Hermit's old C version.
We don't need them and we have no reason to override the defaults here.
See ld [1] for details.

[1]: https://sourceware.org/binutils/docs/ld/Options.htmlSigned-off-by: NMartin Kröning <martin.kroening@eonerc.rwth-aachen.de>

GCC uses the `-fshort-enums` ABI for arm-none and the `int`-sized enum
ABI for arm-linux.
Clang uses the `int`-sized enum ABI for all arm targets.

Both options are permitted by AAPCS.

Rust is matching GCC's behavior for these targets, as interop with code
code compiled by GCC is desirable in the bare-metal context. See #87917.

This option is the same as the `thumb_base` defaults used by this target.

This reverts commit 557359f9, reversing
changes made to 1e6c09a8.

Drop duplicate helper methods on `Layout`, which are already implemented
on `LayoutS`. Note that `Layout` has a `Deref` implementation to
`LayoutS`, so all accessors are automatically redirected.

The methods are identical and have been copied to `rustc_abi` in:

    commit 390a637e
    Author: hamidreza kalbasi <hamidrezakalbasi@protonmail.com>
    Date:   Mon Nov 7 00:36:11 2022 +0330

        move things from rustc_target::abi to rustc_abi

This commit left behind the original implementation. Drop it now.
Signed-off-by: NDavid Rheinsberg <david@readahead.eu>

Tested with the Gaisler bcc2 toolchain (both gcc and clang) and the Leon3 simulator.