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Add neoverse-512tvb optimization build flag and gate it behind CPU detection #82

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Add neoverse-512tvb optimization build flag and gate it behind CPU detection #82

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15 changes: 14 additions & 1 deletion lore-base/build.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,20 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
.includes(Some(native_dir.join("thirdparty")));

if platform == "linux" && arch == "aarch64" {
cc_builder.flag("-mcpu=neoverse-512tvb");
if env::var("LORE_CPU_NEOVERSE_512TVB").is_ok() {
let cpuinfo = std::fs::read_to_string("/proc/cpuinfo").unwrap_or_default();
if cpuinfo.contains("sve2") {
cc_builder.flag("-mcpu=neoverse-512tvb");
} else {
println!(
"cargo:warning=LORE_CPU_NEOVERSE_512TVB is set but SVE2 not detected in /proc/cpuinfo; skipping -mcpu=neoverse-512tvb and building for generic aarch64 to avoid illegal hardware instruction. Disable the `neoverse-512tvb` feature to suppress this warning"
);
}
Comment on lines +31 to +37

@subhramit subhramit Jun 27, 2026 •
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We could also force respecting the flag setting irrespective of cpu info:

Suggested change
if cpuinfo.contains("sve2") {
cc_builder.flag("-mcpu=neoverse-512tvb");
} else {
println!(
"cargo:warning=LORE_CPU_NEOVERSE_512TVB is set but SVE2 not detected in /proc/cpuinfo; skipping -mcpu=neoverse-512tvb and building for generic aarch64 to avoid illegal hardware instruction. Disable the `neoverse-512tvb` feature to suppress this warning"
);
}
if !cpuinfo.contains("sve2") {
println!(
"cargo:warning=LORE_CPU_NEOVERSE_512TVB is set but SVE2 not detected in /proc/cpuinfo; binary may crash with illegal hardware instruction. Unset the `neoverse-512tvb` feature to build for generic aarch64"
);
cc_builder.flag("-mcpu=neoverse-512tvb");
}

in case we are looking forward to cross-compilation cases, so I leave it upto your decision @mjansson @valentina2509

} else {
println!(
"cargo:warning=Building rpmalloc without -mcpu=neoverse-512tvb; binary may be slower on Graviton3+. Set LORE_CPU_NEOVERSE_512TVB=1 to opt in"
);
}
}

if cc_builder.get_compiler().is_like_msvc() {
Expand Down