feat: add succinct-zkvm os and target

compiler/rustc_target/src/spec/mod.rs

@@ -1954,6 +1954,7 @@ supported_targets! {
 
     ("riscv32i-unknown-none-elf", riscv32i_unknown_none_elf),
     ("riscv32im-risc0-zkvm-elf", riscv32im_risc0_zkvm_elf),
+    ("riscv32im-succinct-zkvm-elf", riscv32im_succinct_zkvm_elf),
     ("riscv32im-unknown-none-elf", riscv32im_unknown_none_elf),
     ("riscv32ima-unknown-none-elf", riscv32ima_unknown_none_elf),
     ("riscv32imc-unknown-none-elf", riscv32imc_unknown_none_elf),

compiler/rustc_target/src/spec/targets/riscv32im_succinct_zkvm_elf.rs

@@ -0,0 +1,42 @@
+use crate::spec::{
+    Cc, LinkerFlavor, Lld, PanicStrategy, RelocModel, Target, TargetMetadata, TargetOptions,
+};
+
+pub(crate) fn target() -> Target {
+    Target {
+        data_layout: "e-m:e-p:32:32-i64:64-n32-S128".into(),
+        llvm_target: "riscv32".into(),
+        metadata: TargetMetadata {
+            description: Some("Succinct's zero-knowledge Virtual Machine (RV32IM ISA)".into()),
+            tier: Some(3),
+            host_tools: Some(false),
+            std: None,
+        },
+        pointer_width: 32,
+        arch: "riscv32".into(),
+
+        options: TargetOptions {
+            os: "succinct-zkvm".into(),
+            vendor: "succinct".into(),
+            linker_flavor: LinkerFlavor::Gnu(Cc::No, Lld::Yes),
+            linker: Some("rust-lld".into()),
+            cpu: "generic-rv32".into(),
+
+            // The zkvm is singlethreaded and all operations are atomic.
+            // The std-lib is compiled with lowered atomicsa and the default Succinct build tools
+            // enforce this on programs.
+            max_atomic_width: Some(64),
+            atomic_cas: true,
+
+            features: "+m".into(),
+            llvm_abiname: "ilp32".into(),
+            executables: true,
+            panic_strategy: PanicStrategy::Abort,
+            relocation_model: RelocModel::Static,
+            emit_debug_gdb_scripts: false,
+            eh_frame_header: false,
+            singlethread: true,
+            ..Default::default()
+        },
+    }
+}

src/bootstrap/src/core/sanity.rs

@@ -35,6 +35,7 @@ pub struct Finder {
 const STAGE0_MISSING_TARGETS: &[&str] = &[
     // just a dummy comment so the list doesn't get onelined
     "wasm32-wali-linux-musl",
+    "riscv32im-succinct-zkvm-elf",
 ];
 
 /// Minimum version threshold for libstdc++ required when using prebuilt LLVM

src/doc/rustc/src/SUMMARY.md

@@ -77,6 +77,7 @@
     - [riscv32e\*-unknown-none-elf](platform-support/riscv32e-unknown-none-elf.md)
     - [riscv32i\*-unknown-none-elf](platform-support/riscv32-unknown-none-elf.md)
     - [riscv32im-risc0-zkvm-elf](platform-support/riscv32im-risc0-zkvm-elf.md)
+    - [riscv32im-succinct-zkvm-elf](platform-support/riscv32im-succinct-zkvm-elf.md)
     - [riscv32imac-unknown-xous-elf](platform-support/riscv32imac-unknown-xous-elf.md)
     - [riscv64gc-unknown-linux-gnu](platform-support/riscv64gc-unknown-linux-gnu.md)
     - [riscv64gc-unknown-linux-musl](platform-support/riscv64gc-unknown-linux-musl.md)

src/doc/rustc/src/platform-support/riscv32im-succinct-zkvm-elf.md

@@ -0,0 +1,83 @@
+# `riscv32im-risc0-zkvm-elf`
+
+**Tier: 3**
+
+Succinct's ISA for the SP1 zkVM (Zero Knowledge Virtual Machine).
+
+## Target maintainers
+
+- John Guibas, `john@succinct.xyz`, https://github.com/jtguibas
+- Nathan Bustamante, `nathan@succinct.xyz`, https://github.com/nhtyy
+
+## Background
+
+This target is an execution environment to produce a proof of execution of
+a RISC-V ELF binary and any output that the developer of the binary wishes to
+display publicly. In order to do this, the target will execute the ELF and
+create a cryptographic proof of the "trace" of the programs runtime.
+
+We have a cargo extension called [cargo-prove] that allow users to generate
+project templates, install tools for improved user experience and build binaries.
+
+## Requirements
+
+The target only supports cross compilation and no host tools. The target
+supports `alloc` with a default allocator and will have support for std soon.
+
+The target's execution environment is single threaded, non-preemptive, and does
+not support any privileged instructions, nor unaligned accesses. At the time of
+writing the VM has 192 MB of memory and text/data, heap, and stack need to be
+with in the address range `0x400` - `0x0C000000`. The binaries themselves expect
+no operating system and can be thought of as running on bare-metal. The target
+does not use `#[target_feature(...)]` or `-C target-feature=` values.
+
+Calling `extern "C"` on the target uses the C calling convention outlined in the
+[RISC-V specification].
+
+## Building for the zkVM
+
+Programs for the zkVM could be built by adding it to the `target` list in
+`config.toml`. However, we recommend building programs in our starter template
+generated by the [cargo-prove] utility and the [sp1-build] crate. This
+crate calls `rustc` with `-C "link-arg=-Ttext=` so that it maps the text in the
+appropriate location as well as generating variables that represent the ELF and
+a unique ID associated with the ELF.
+
+The starter template provides developers with system calls that are useful
+to zero knowledge computing such as writing to
+the public output, hashing using sha256, and multiply big integers.
+
+## Building Rust programs
+
+Rust does not yet ship pre-compiled artifacts for this target. To compile for
+this target, you will either need to build Rust with the target enabled (see
+"Building the target" above). We do not recommend using `build-std` as we have
+run into issues building core in the past on our starter template. An alternate
+solution is to download the risc0 tool chain by running `cargo prove install-toolchain`.
+
+## Testing
+
+Note: the target is implemented as a software emulator called the zkVM and there
+is no hardware implementation of the target.
+
+The most practical way to test the target program is to use our starter template
+that can be generated by using the `cargo prove new` command. The template
+generates a sample "host" and "guest" code. The guest code compiled to the
+target (which is RV32IM) whereas the "host" code is compiled to run on the
+programmer's machine running either a Linux distribution or macOS.
+
+The host program is responsible for running the guest binary on the zkVM and retrieving
+its public output.
+
+The target currently does not support running the Rust test suite.
+
+## Cross-compilation toolchains and C code
+
+Compatible C code can be built for this target on any compiler that has a RV32IM
+target.  On clang and ld.lld linker, it can be generated using the
+`-march=rv32im`, `-mabi=ilp32` with llvm features flag `features=+m` and llvm
+target `riscv32-unknown-none`.
+
+[RISC-V specification]: https://riscv.org/wp-content/uploads/2015/01/riscv-calling.pdf
+[cargo-prove]: https://docs.succinct.xyz/docs/sp1/getting-started/install
+[sp1-build]: https://crates.io/crates/sp1-build

src/tools/build-manifest/src/main.rs

@@ -138,6 +138,7 @@ static TARGETS: &[&str] = &[
     "powerpc64le-unknown-linux-musl",
     "riscv32i-unknown-none-elf",
     "riscv32im-risc0-zkvm-elf",
+    "riscv32im-succinct-zkvm-elf",
     "riscv32im-unknown-none-elf",
     "riscv32ima-unknown-none-elf",
     "riscv32imc-unknown-none-elf",

tests/assembly/targets/targets-elf.rs

@@ -421,6 +421,9 @@
 //@ revisions: riscv32im_risc0_zkvm_elf
 //@ [riscv32im_risc0_zkvm_elf] compile-flags: --target riscv32im-risc0-zkvm-elf
 //@ [riscv32im_risc0_zkvm_elf] needs-llvm-components: riscv
+//@ revisions: riscv32im_succinct_zkvm_elf
+//@ [riscv32im_succinct_zkvm_elf] compile-flags: --target riscv32im-succinct-zkvm-elf
+//@ [riscv32im_succinct_zkvm_elf] needs-llvm-components: riscv
 //@ revisions: riscv32im_unknown_none_elf
 //@ [riscv32im_unknown_none_elf] compile-flags: --target riscv32im-unknown-none-elf
 //@ [riscv32im_unknown_none_elf] needs-llvm-components: riscv