From 61e1483b74da8511ccc4eef4d9b1c7de2ef680a0 Mon Sep 17 00:00:00 2001
From: Kamil Rakoczy <krakoczy@antmicro.com>
Date: Fri, 5 May 2023 14:36:20 +0200
Subject: [PATCH] Add multi-threaded Verilating at emit stage (#3608)

---
 src/V3EmitCImp.cpp | 29 ++++++++++++++++++++++-------
 1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/src/V3EmitCImp.cpp b/src/V3EmitCImp.cpp
index 679f392ce..5574613d6 100644
--- a/src/V3EmitCImp.cpp
+++ b/src/V3EmitCImp.cpp
@@ -22,6 +22,7 @@
 #include "V3EmitCFunc.h"
 #include "V3Global.h"
 #include "V3String.h"
+#include "V3ThreadPool.h"
 #include "V3UniqueNames.h"
 
 #include <map>
@@ -145,7 +146,7 @@ class EmitCGatherDependencies final : VNVisitorConst {
     }
 
 public:
-    static const std::set<std::string> gather(AstCFunc* cfuncp) {
+    static const std::set<std::string> gather(AstCFunc* cfuncp) VL_MT_STABLE {
         const EmitCGatherDependencies visitor{cfuncp};
         return std::move(visitor.m_dependencies);
     }
@@ -564,7 +565,8 @@ class EmitCImp final : EmitCFunc {
     ~EmitCImp() override = default;
 
 public:
-    static void main(const AstNodeModule* modp, bool slow, std::deque<AstCFile*>& cfilesr) {
+    static void main(const AstNodeModule* modp, bool slow,
+                     std::deque<AstCFile*>& cfilesr) VL_MT_STABLE {
         EmitCImp{modp, slow, cfilesr};
     }
 };
@@ -908,7 +910,7 @@ class EmitCTrace final : EmitCFunc {
     ~EmitCTrace() override = default;
 
 public:
-    static void main(AstNodeModule* modp, bool slow, std::deque<AstCFile*>& cfilesr) {
+    static void main(AstNodeModule* modp, bool slow, std::deque<AstCFile*>& cfilesr) VL_MT_STABLE {
         EmitCTrace{modp, slow, cfilesr};
     }
 };
@@ -921,24 +923,37 @@ void V3EmitC::emitcImp() {
     // Make parent module pointers available.
     const EmitCParentModule emitCParentModule;
     std::list<std::deque<AstCFile*>> cfiles;
+    std::list<std::future<void>> futures;
 
     // Process each module in turn
     for (const AstNode* nodep = v3Global.rootp()->modulesp(); nodep; nodep = nodep->nextp()) {
         if (VN_IS(nodep, Class)) continue;  // Imped with ClassPackage
         const AstNodeModule* const modp = VN_AS(nodep, NodeModule);
         cfiles.emplace_back();
-        EmitCImp::main(modp, /* slow: */ true, cfiles.back());
+        auto& slowCfilesr = cfiles.back();
+        futures.push_back(V3ThreadPool::s().enqueue<void>(
+            [modp, &slowCfilesr]() { EmitCImp::main(modp, /* slow: */ true, slowCfilesr); }));
         cfiles.emplace_back();
-        EmitCImp::main(modp, /* slow: */ false, cfiles.back());
+        auto& fastCfilesr = cfiles.back();
+        futures.push_back(V3ThreadPool::s().enqueue<void>(
+            [modp, &fastCfilesr]() { EmitCImp::main(modp, /* slow: */ false, fastCfilesr); }));
     }
 
     // Emit trace routines (currently they can only exist in the top module)
     if (v3Global.opt.trace() && !v3Global.opt.lintOnly()) {
         cfiles.emplace_back();
-        EmitCTrace::main(v3Global.rootp()->topModulep(), /* slow: */ true, cfiles.back());
+        auto& slowCfilesr = cfiles.back();
+        futures.push_back(V3ThreadPool::s().enqueue<void>([&slowCfilesr]() {
+            EmitCTrace::main(v3Global.rootp()->topModulep(), /* slow: */ true, slowCfilesr);
+        }));
         cfiles.emplace_back();
-        EmitCTrace::main(v3Global.rootp()->topModulep(), /* slow: */ false, cfiles.back());
+        auto& fastCfilesr = cfiles.back();
+        futures.push_back(V3ThreadPool::s().enqueue<void>([&fastCfilesr]() {
+            EmitCTrace::main(v3Global.rootp()->topModulep(), /* slow: */ false, fastCfilesr);
+        }));
     }
+    // Wait for futures
+    V3ThreadPool::waitForFutures(futures);
     for (const auto& collr : cfiles) {
         for (const auto cfilep : collr) v3Global.rootp()->addFilesp(cfilep);
     }