flake: Enable thread-safe mode for LLVM

This is required as we use the LLVM APIs from multiple threads.

nac3artiq/src/lib.rs

@@ -9,6 +9,7 @@ use inkwell::{
     memory_buffer::MemoryBuffer,
     module::{Linkage, Module},
     passes::PassBuilderOptions,
+    support::is_multithreaded,
     targets::*,
     OptimizationLevel,
 };
@@ -582,7 +583,8 @@ impl Nac3 {
             membuffer.lock().push(buffer);
         })));
         let size_t = if self.isa == Isa::Host { 64 } else { 32 };
-        let thread_names: Vec<String> = (0..4).map(|_| "main".to_string()).collect();
+        let num_threads = if is_multithreaded() { 4 } else { 1 };
+        let thread_names: Vec<String> = (0..num_threads).map(|_| "main".to_string()).collect();
         let threads: Vec<_> = thread_names
             .iter()
             .map(|s| Box::new(ArtiqCodeGenerator::new(s.to_string(), size_t, self.time_fns)))

nac3standalone/src/main.rs

@@ -2,6 +2,7 @@ use clap::Parser;
 use inkwell::{
     memory_buffer::MemoryBuffer,
     passes::PassBuilderOptions,
+    support::is_multithreaded,
     targets::*,
     OptimizationLevel,
 };
@@ -39,7 +40,7 @@ struct CommandLineArgs {
     file_name: String,
 
     /// The number of threads allocated to processing the source file.
-    #[arg(default_value_t = 1)]
+    #[arg(short = 'T', default_value_t = 1)]
     threads: u32,
 
     /// The level to optimize the LLVM IR.
@@ -207,6 +208,14 @@ fn main() {
         .map(|arg| if arg == "native" { host_target_machine.cpu.clone() } else { arg })
         .unwrap_or_default();
     let target_features = target_features.unwrap_or_default();
+    let threads = if is_multithreaded() {
+        threads
+    } else {
+        if threads > 1 {
+            println!("Warning: Number of threads specified in command-line but multithreading is disabled in LLVM at build time! Defaulting to single-threaded compilation")
+        }
+        1
+    };
     let opt_level = match opt_level {
         0 => OptimizationLevel::None,
         1 => OptimizationLevel::Less,

nix/llvm/default.nix

@@ -112,7 +112,7 @@ in stdenv.mkDerivation (rec {
     "-DLLVM_HOST_TRIPLE=${stdenv.hostPlatform.config}"
     "-DLLVM_DEFAULT_TARGET_TRIPLE=${stdenv.hostPlatform.config}"
     "-DLLVM_ENABLE_UNWIND_TABLES=OFF"
-    "-DLLVM_ENABLE_THREADS=OFF"
+    "-DLLVM_ENABLE_THREADS=ON"
     "-DLLVM_INCLUDE_BENCHMARKS=OFF"
     "-DLLVM_BUILD_TOOLS=OFF"
     "-DLLVM_TARGETS_TO_BUILD=X86;ARM;RISCV"