factor out RISCV support from the guts_api branchguts_riscv

TODO: figure out what environment variable should enable this

1 files changed, 59 insertions, 0 deletions

diff --git a/rust/guts/build.rs b/rust/guts/build.rs
new file mode 100644
index 0000000..f0ef0e2
--- /dev/null
+++ b/rust/guts/build.rs
@@ -0,0 +1,59 @@
+use std::env;
+
+fn defined(var: &str) -> bool {
+    println!("cargo:rerun-if-env-changed={}", var);
+    env::var_os(var).is_some()
+}
+
+fn is_pure() -> bool {
+    defined("CARGO_FEATURE_PURE")
+}
+
+fn target_components() -> Vec<String> {
+    let target = env::var("TARGET").unwrap();
+    target.split("-").map(|s| s.to_string()).collect()
+}
+
+fn is_riscv64gc() -> bool {
+    target_components()[0] == "riscv64gc"
+}
+
+fn new_build() -> cc::Build {
+    let build = cc::Build::new();
+    build
+}
+
+fn build_riscv_rva23u64_assembly() {
+    println!("cargo:rustc-cfg=blake3_riscv_rva23u64_ffi");
+    let mut build = new_build();
+    let asm_path = "src/riscv_rva23u64.S";
+    build.file(asm_path);
+    build.flag("--target=riscv64");
+    build.flag("-march=rv64gcv_zbb_zvbb1p0");
+    build.flag("-menable-experimental-extensions");
+    build.compile("blake3_riscv_rva23u64_assembly");
+    println!("cargo:rerun-if-changed={asm_path}");
+}
+
+fn main() {
+    // TODO: This implementation assumes some bleeding-edge extensions, and it should probably be
+    // gated by a Cargo feature.
+    if is_riscv64gc() && !is_pure() {
+        build_riscv_rva23u64_assembly();
+    }
+
+    // The `cc` crate doesn't automatically emit rerun-if directives for the
+    // environment variables it supports, in particular for $CC. We expect to
+    // do a lot of benchmarking across different compilers, so we explicitly
+    // add the variables that we're likely to need.
+    println!("cargo:rerun-if-env-changed=CC");
+    println!("cargo:rerun-if-env-changed=CFLAGS");
+
+    // Ditto for source files, though these shouldn't change as often.
+    for file in std::fs::read_dir("../../c").unwrap() {
+        println!(
+            "cargo:rerun-if-changed={}",
+            file.unwrap().path().to_str().expect("utf-8")
+        );
+    }
+}