ARM Support

[realchonk]

Build Instructions

First build/get an arm-linux musl toolchain (like from https://toolchains.bootlin.com/, if you're on Linux).

export CC=/opt/armv7-eabihf--musl--stable-2024.05-1/bin/arm-buildroot-linux-musleabihf-gcc # for the bootlin toolchain
export RUSTC_VERSION=1.74.0 MRUSTC_TARGET_VER=1.74 MRUSTC_TARGET=arm-linux-musl

make RUSTCSTR # download rustc source
make -j16 # build mrustc
make -j16 LIBS # build minicargo and libstd

Building libcore fails

--- BUILDING core v0.0.0 (0.0% 1r,0w,18b,0c/19t)
> /home/benni/src/mrustc/bin/mrustc /home/benni/src/mrustc/rustc-1.74.0-src/library/core/src/lib.rs -o output-1.74.0-arm-linux-musl/libcore.rlib -C emit-depfile=output-1.74.0-arm-linux-musl/libcore.rlib.d --cfg
debug_assertions -O -L output-1.74.0-arm-linux-musl -L output-1.74.0-arm-linux-musl/host --crate-name core --crate-type rlib --crate-tag 0_0_0 --target arm-linux-musl -C emit-build-command=output-1.74.0-arm-linux-musl/libcore.rlib.sh --edition 2021 > output-1.74.0-arm-linux-musl/libcore.rlib_dbg.txt
 (0.0% 1r,0w,18b,0c/19t): core v0.0.0
MIR TODO: <*const u8 /*- <u8,>*/>::wrapping_offset BB0/TERM: Call intrinsic "arith_offset" - Call( retval = "arith_offset"::<T/*I:0*/,>( a0, a1, ), bb1, bb2)
Process was terminated with signal 6
FAILING COMMAND: /home/benni/src/mrustc/bin/mrustc /home/benni/src/mrustc/rustc-1.74.0-src/library/core/src/lib.rs -o output-1.74.0-arm-linux-musl/libcore.rlib -C emit-depfile=output-1.74.0-arm-linux-musl/libcore.rlib.d --cfg debug_assertions -O -L output-1.74.0-arm-linux-musl -L output-1.74.0-arm-linux-musl/host --crate-name core --crate-type rlib --crate-tag 0_0_0 --target arm-linux-musl -C emit-build-command=output-1.74.0-arm-linux-musl/libcore.rlib.sh --edition 2021
Env:  OUT_DIR=/home/benni/src/mrustc/output-1.74.0-arm-linux-musl/build_core CARGO_MANIFEST_DIR=/home/benni/src/mrustc/rustc-1.74.0-src/library/core CARGO_PKG_NAME=core CARGO_PKG_VERSION=0.0.0 CARGO_PKG_VERSION_MAJOR=0 CARGO_PKG_VERSION_MINOR=0 CARGO_PKG_VERSION_PATCH=0
 (5.3% 0r,0w,18b,1c/19t):
BUILD FAILED

TODO

• add intrinsics:
  • arith_offset<T>(ptr: *const T, off: isize) -> *const T

@thepowersgang would you be able to help me with this?

[realchonk]

Applying the following patch, leads to a different compiler error, not sure if they are related:

Patch

diff --git a/src/hir_conv/constant_evaluation.cpp b/src/hir_conv/constant_evaluation.cpp
index 88255837..80881eff 100644
--- a/src/hir_conv/constant_evaluation.cpp
+++ b/src/hir_conv/constant_evaluation.cpp
@@ -2879,7 +2879,7 @@ namespace HIR {
                     auto vr_dst = ValueRef(ptr_dst.second, ptr_dst.first - EncodedLiteral::PTR_BASE).slice(0, nbytes);
                     vr_dst.copy_from(state, vr_src);
                 }
-                else if( te->name == "offset" ) {
+                else if( te->name == "offset" || te->name == "arith_offset" ) {
                     auto ty = local_state.monomorph_expand(te->params.m_types.at(0).data().as_Pointer().inner);
                     size_t element_size;
                     if( !Target_GetSizeOf(state.sp, resolve, ty, element_size) )

Error

$ make LIBS
make -f minicargo.mk LIBS
make[1]: Entering directory '/home/benni/src/mrustc'
make -f Makefile all
make -C tools/minicargo/
make[2]: Entering directory '/home/benni/src/mrustc'
make[2]: Entering directory '/home/benni/src/mrustc/tools/minicargo'
make[2]: Nothing to be done for 'all'.
make[2]: Leaving directory '/home/benni/src/mrustc/tools/minicargo'
test -e bin/minicargo
make[2]: Nothing to be done for 'all'.
make[2]: Leaving directory '/home/benni/src/mrustc'
test -e bin/mrustc
bin/minicargo --vendor-dir rustc-1.74.0-src/vendor --script-overrides script-overrides/stable-1.74.0-linux/ --output-dir output-1.74.0-arm-linux-musl/ --target arm-linux-musl --manifest-overrides rustc-1.74.0-overrides.toml rustc-1.74.0-src/mrustc-stdlib/
warning: rustc-1.74.0-src/vendor/object/Cargo.toml:33: Unknown key `resolver` in [package]
warning: rustc-1.74.0-src/vendor/zeroize/Cargo.toml:42: Unknown key `resolver` in [package]
warning: rustc-1.74.0-src/vendor/derive_arbitrary/Cargo.toml:37: Unknown key `resolver` in [package]
warning: rustc-1.74.0-src/vendor/gimli/Cargo.toml:42: Unknown key `resolver` in [package]
--- BUILDING core v0.0.0 (0.0% 1r,0w,18b,0c/19t)
> /home/benni/src/mrustc/bin/mrustc /home/benni/src/mrustc/rustc-1.74.0-src/library/core/src/lib.rs -o output-1.74.0-arm-linux-musl/libcore.rlib -C emit-depfile=output-1.74.0-arm-linux-musl/libcore.rlib.d --cfg
debug_assertions -O -L output-1.74.0-arm-linux-musl -L output-1.74.0-arm-linux-musl/host --crate-name core --crate-type rlib --crate-tag 0_0_0 --target arm-linux-musl -C emit-build-command=output-1.74.0-arm-linux-musl/libcore.rlib.sh --edition 2021 > output-1.74.0-arm-linux-musl/libcore.rlib_dbg.txt
 (0.0% 1r,0w,18b,0c/19t): core v0.0.0
mrustc: src/hir/type.hpp:201: const HIR::TypeData::Data_Pointer& HIR::TypeData::as_Pointer() const: Assertion `m_tag == TAG_Pointer' failed.
Process was terminated with signal 6
FAILING COMMAND: /home/benni/src/mrustc/bin/mrustc /home/benni/src/mrustc/rustc-1.74.0-src/library/core/src/lib.rs -o output-1.74.0-arm-linux-musl/libcore.rlib -C emit-depfile=output-1.74.0-arm-linux-musl/libcore.rlib.d --cfg debug_assertions -O -L output-1.74.0-arm-linux-musl -L output-1.74.0-arm-linux-musl/host --crate-name core --crate-type rlib --crate-tag 0_0_0 --target arm-linux-musl -C emit-build-command=output-1.74.0-arm-linux-musl/libcore.rlib.sh --edition 2021
Env:  OUT_DIR=/home/benni/src/mrustc/output-1.74.0-arm-linux-musl/build_core CARGO_MANIFEST_DIR=/home/benni/src/mrustc/rustc-1.74.0-src/library/core CARGO_PKG_NAME=core CARGO_PKG_VERSION=0.0.0 CARGO_PKG_VERSION_MAJOR=0 CARGO_PKG_VERSION_MINOR=0 CARGO_PKG_VERSION_PATCH=0
 (5.3% 0r,0w,18b,1c/19t):
BUILD FAILED
make[1]: *** [minicargo.mk:236: LIBS] Error 1
make[1]: Leaving directory '/home/benni/src/mrustc'
make: *** [Makefile:158: LIBS] Error 2

[thepowersgang]

Run in a debugger to find out where that as_Pointer call is, it may be somewhere in constant evaluation.

[realchonk]

The line if fails to compile is apprently this rustc-1.74.0-src/library/core/src/ascii/ascii_char.rs:587

const HEX_DIGITS: [AsciiChar; 16] = *b"0123456789abcdef".as_ascii().unwrap();

It doesn't make sense, because the exact same setup works for RISC-V and native, but not for ARM.
I think it's a different issue, but I can't figure out what it is.
Why would it try to constantly evaluate the arith_offset() intrinsic only on ARM?

For context: The arith_offset() intrinsic is used by std::ptr::wrapping_add(), which is used in is_ascii()