Switch to the correct RISC-V toolchain

Author: lrettig

build.sh

@@ -5,16 +5,64 @@ set -euo pipefail
 source config.sh
 
 # Fail fast if these tools aren't properly installed and in the path
-need_cmd riscv64-unknown-elf-gcc
-need_cmd riscv64-unknown-elf-g++
+need_cmd riscv32-unknown-elf-clang
+need_cmd riscv32-unknown-elf-clang++
 
 # Rust requires a custom target file to exist for our custom target as part of the bootstrap build,
 # but it doesn't actually look at the contents.
-touch /tmp/riscv32em-athena-zkvm-elf.json
+cat > /tmp/riscv32em-athena-zkvm-elf.json << EOF
+{
+  "arch": "riscv32",
+  "cpu": "generic-rv32",
+  "crt-objects-fallback": "false",
+  "data-layout": "e-m:e-p:32:32-i64:64-n32-S32",
+  "eh-frame-header": false,
+  "emit-debug-gdb-scripts": false,
+  "features": "+e,+m",
+  "linker": "rust-lld",
+  "linker-flavor": "gnu-lld",
+  "llvm-abiname": "ilp32e",
+  "llvm-target": "riscv32",
+  "max-atomic-width": 32,
+  "os": "zkvm",
+  "panic-strategy": "abort",
+  "relocation-model": "static",
+  "singlethread": true,
+  "target-pointer-width": "32",
+  "vendor": "athena",
+  "options": {
+    "c-flags": "-march=rv32e -mabi=ilp32e",
+    "pre-link-args": {
+      "gcc": [
+        "-march=rv32e",
+        "-mabi=ilp32e"
+      ]
+    }
+  }
+}
+EOF
+
+# Set environment variables to override compiler flags
+export CC_riscv32em_athena_zkvm_elf="riscv32-unknown-elf-clang"
+export CXX_riscv32em_athena_zkvm_elf="riscv32-unknown-elf-clang++"
+export AR_riscv32em_athena_zkvm_elf="riscv32-unknown-elf-ar"
+
+# Explicitly set CFLAGS without the problematic flags
+export CFLAGS_riscv32em_athena_zkvm_elf="-ffunction-sections -fdata-sections -fPIC -target riscv32-unknown-elf"
+export CXXFLAGS_riscv32em_athena_zkvm_elf="$CFLAGS_riscv32em_athena_zkvm_elf"
+
+# Set Rust flags
+export CARGO_TARGET_RISCV32EM_ATHENA_ZKVM_ELF_RUSTFLAGS="-Cpasses=loweratomic -Clink-arg=-march=rv32em -Clink-arg=-mabi=ilp32e"
+
+# Override the default target for compiler-rt
+export COMPILER_RT_DEFAULT_TARGET_TRIPLE="riscv32-unknown-elf"
+
+# Force the use of our custom target spec
+export RUST_TARGET_PATH="/tmp"
+
+# Prevent the build system from adding --target flag
+export RUSTC_TARGET_ARG=""
 
 # Will create component archives (dists) ./rust/build/dist
 cd rust
-RUST_TARGET_PATH="/tmp" \
-CARGO_TARGET_RISCV32EM_ATHENA_ZKVM_ELF_RUSTFLAGS="-Cpasses=loweratomic" \
-CFLAGS_riscv32em_athena_zkvm_elf="-ffunction-sections -fdata-sections -fPIC -march=rv32em -mabi=ilp32e" \
 ./x build --stage 2

patches/config.toml

@@ -7,8 +7,10 @@ tools = ["cargo", "cargo-clippy", "clippy", "rustfmt"]
 configure-args = []
 
 [target.riscv32em-athena-zkvm-elf]
-cc = "riscv64-unknown-elf-gcc"
-cxx = "riscv64-unknown-elf-g++"
+cc = "riscv32-unknown-elf-clang"
+cxx = "riscv32-unknown-elf-clang++"
+linker = "riscv32-unknown-elf-gcc"
+ar = "riscv32-unknown-elf-ar"
 
 [rust]
 lld = true