From 7fc2a30c147dd151b7a01b8cd2d936b07f4a3e49 Mon Sep 17 00:00:00 2001
From: David Mak <csdavidmak@ust.hk>
Date: Fri, 13 Oct 2023 11:28:30 +0800
Subject: [PATCH] Force single-threaded compilation if LLVM is not thread-safe

---
 nac3artiq/src/lib.rs       |  4 +++-
 nac3standalone/src/main.rs | 18 +++++++++++++-----
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/nac3artiq/src/lib.rs b/nac3artiq/src/lib.rs
index 68e837bdc..bef1e73a2 100644
--- a/nac3artiq/src/lib.rs
+++ b/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)))
diff --git a/nac3standalone/src/main.rs b/nac3standalone/src/main.rs
index 97d8d9ec4..9deb34ec2 100644
--- a/nac3standalone/src/main.rs
+++ b/nac3standalone/src/main.rs
@@ -2,6 +2,7 @@ use clap::Parser;
 use inkwell::{
     memory_buffer::MemoryBuffer,
     passes::PassBuilderOptions,
+    support::is_multithreaded,
     targets::*,
     OptimizationLevel,
 };
@@ -210,12 +211,19 @@ 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 threads == 0 {
-        std::thread::available_parallelism()
-            .map(|threads| threads.get() as u32)
-            .unwrap_or(1u32)
+    let threads = if is_multithreaded() {
+        if threads == 0 {
+            std::thread::available_parallelism()
+                .map(|threads| threads.get() as u32)
+                .unwrap_or(1u32)
+        } else {
+            threads
+        }
     } else {
-        threads
+        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,