flake: Enable thread-safe mode for LLVM

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

nac3standalone/demo/run_demo.sh

@@ -31,9 +31,8 @@ else
     nac3standalone=../../target/x86_64-unknown-linux-gnu/release/nac3standalone
 fi
 
+rm -f ./*.o ./*.bc demo
 if [ -z "$use_lli" ]; then
-  rm -f "*.o" demo
-
   $nac3standalone "${nac3args[@]}"
 
   clang -c -std=gnu11 -Wall -Wextra -O3 -o demo.o demo.c
@@ -45,15 +44,19 @@ if [ -z "$use_lli" ]; then
     ./demo > "$outfile"
   fi
 else
-  rm -f "*.o" "*.bc" demo
-
   $nac3standalone --emit-llvm "${nac3args[@]}"
 
   clang -c -std=gnu11 -Wall -Wextra -O3 -emit-llvm -o demo.bc demo.c
 
-  if [ -z "$outfile" ]; then
-    lli --extra-module demo.bc --extra-module irrt.bc main.bc
+  if ls module*.bc >/dev/null 2>&1; then
+    llvm-link -o module.bc module*.bc main.bc
   else
-    lli --extra-module demo.bc --extra-module irrt.bc main.bc > "$outfile"
+    cp main.bc module.bc
+  fi
+
+  if [ -z "$outfile" ]; then
+    lli --extra-module demo.bc --extra-module irrt.bc module.bc
+  else
+    lli --extra-module demo.bc --extra-module irrt.bc module.bc > "$outfile"
   fi
 fi

nac3standalone/src/main.rs

@@ -39,8 +39,9 @@ struct CommandLineArgs {
     /// The name of the input file.
     file_name: String,
 
-    /// The number of threads allocated to processing the source file.
-    #[arg(default_value_t = 1)]
+    /// The number of threads allocated to processing the source file. If 0 is passed to this
+    /// parameter, all available threads will be used for compilation.
+    #[arg(short = 'T', default_value_t = 1)]
     threads: u32,
 
     /// The level to optimize the LLVM IR.
@@ -48,6 +49,8 @@ struct CommandLineArgs {
     opt_level: u32,
 
     /// Whether to emit LLVM IR at the end of every module.
+    ///
+    /// If multithreaded compilation is also enabled, each thread will emit its own module.
     #[arg(long, default_value_t = false)]
     emit_llvm: bool,
 
@@ -209,9 +212,15 @@ fn main() {
         .unwrap_or_default();
     let target_features = target_features.unwrap_or_default();
     let threads = if is_multithreaded() {
-        threads
+        if threads == 0 {
+            std::thread::available_parallelism()
+                .map(|threads| threads.get() as u32)
+                .unwrap_or(1u32)
+        } else {
+            threads
+        }
     } else {
-        if threads > 1 {
+        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