From 7ba6cfe65181bbf85784e9eae576f894cf18dfe2 Mon Sep 17 00:00:00 2001
From: Tony Wasserka <neobrain@users.noreply.github.com>
Date: Tue, 16 Dec 2025 11:32:03 +0100
Subject: [PATCH] FEXServer: Implement automatic code cache generation

---
 Source/Tools/FEXServer/ProcessPipe.cpp | 71 ++++++++++++++++++++++----
 1 file changed, 61 insertions(+), 10 deletions(-)

diff --git a/Source/Tools/FEXServer/ProcessPipe.cpp b/Source/Tools/FEXServer/ProcessPipe.cpp
index 3d7dfbeaf..26f189d6d 100644
--- a/Source/Tools/FEXServer/ProcessPipe.cpp
+++ b/Source/Tools/FEXServer/ProcessPipe.cpp
@@ -24,6 +24,7 @@
 #include <sys/resource.h>
 #include <sys/socket.h>
 #include <sys/un.h>
+#include <sys/wait.h>
 #include <vector>
 
 #include <xxhash.h>
@@ -371,7 +372,7 @@ static void WriteNewCodeMap(const FEXCore::ExecutableFileInfo& File, const std::
     // List the main executable and all used libraries
     OutputCodeMap.AppendSetMainExecutable(File);
 
-    for (auto& Dependency : Dependencies) {
+    for (auto& [Dependency, _] : Dependencies) {
       OutputCodeMap.AppendLibraryLoad(Dependency);
     }
   } else {
@@ -384,27 +385,37 @@ static void WriteNewCodeMap(const FEXCore::ExecutableFileInfo& File, const std::
   }
 }
 
+enum class NeedsCacheRefresh {
+  No,
+  Yes,
+};
+
 /**
  * Checks and processes new code maps generated by FEX for the given application.
  *
  * Processed code maps are merged into the reference code map and deleted afterwards.
+ *
+ * The returned map is a list of all dependencies of the main executables discovered,
+ * associated with a flag to indicate need for cache regeneration.
  */
-static void AggregateCodeMaps(const FEXCore::ExecutableFileInfo& MainFileId, bool HasMultiblock) {
-  std::set<FEXCore::ExecutableFileInfo> Result;
+static std::map<FEXCore::ExecutableFileInfo, NeedsCacheRefresh> AggregateCodeMaps(const FEXCore::ExecutableFileInfo& MainFileId, bool HasMultiblock) {
+  std::map<FEXCore::ExecutableFileInfo, NeedsCacheRefresh> Result;
 
   // Read all dependencies discovered in previous runs
   {
     auto MainFileCodeMapPath = fmt::format("{}/ready/{}", CodeMapDirectory, FEXCore::CodeMap::GetBaseFilename(MainFileId, !HasMultiblock));
     std::ifstream MainFileCodeMap(MainFileCodeMapPath, std::ios_base::binary);
     for (auto& [FileId, Contents] : FEXCore::CodeMap::ParseCodeMap(MainFileCodeMap)) {
-      Result.emplace(nullptr, FileId, Contents.Filename);
+      Result.emplace(std::piecewise_construct, std::forward_as_tuple(nullptr, FileId, Contents.Filename),
+                     std::forward_as_tuple(NeedsCacheRefresh::No));
     }
   }
 
   // Accumulate information from new code maps
   auto IncomingCodeMap = ImportPendingCodeMaps(MainFileId, HasMultiblock);
   for (auto& [File, _] : IncomingCodeMap) {
-    Result.emplace(nullptr, File.FileId, File.Filename);
+    Result.emplace(std::piecewise_construct, std::forward_as_tuple(nullptr, File.FileId, File.Filename),
+                   std::forward_as_tuple(NeedsCacheRefresh::No));
   }
 
   // For each referenced library, add referenced offsets to that library's reference code map
@@ -425,12 +436,40 @@ static void AggregateCodeMaps(const FEXCore::ExecutableFileInfo& MainFileId, boo
       }
     }
 
-    // Update code map
-    std::set<FEXCore::ExecutableFileInfo> Empty;
+    // Update code map and queue for cache generation
+    std::map<FEXCore::ExecutableFileInfo, NeedsCacheRefresh> Empty;
     WriteNewCodeMap(File, OutputName, Blocks, true, File.FileId == MainFileId.FileId ? Result : Empty);
+    Result.at(File) = NeedsCacheRefresh::Yes;
   }
+
+  return Result;
 }
 
+int32_t EmbedSubprocess(const char* path, char* const* args) {
+  pid_t pid = fork();
+  if (pid == 0) {
+    execvp(path, args);
+    _exit(-1);
+  } else {
+    int32_t Status {};
+    while (waitpid(pid, &Status, 0) == -1 && errno == EINTR)
+      ;
+    if (WIFEXITED(Status)) {
+      return (int8_t)WEXITSTATUS(Status);
+    }
+  }
+
+  return -1;
+}
+
+/**
+ * Spawn a FEXOfflineCompiler instance to generate a code cache from the given code map
+ */
+static int RunOfflineCompiler(const char* CodeMap) {
+  const char* ExecveArgs[] = {"FEXOfflineCompiler", "generate", CodeMap, nullptr};
+  return EmbedSubprocess("FEXOfflineCompiler", const_cast<char* const*>(&ExecveArgs[0]));
+};
+
 void HandleSocketData(fasio::tcp_socket& Socket) {
   std::vector<uint8_t> Data(1500);
 
@@ -554,10 +593,22 @@ void HandleSocketData(fasio::tcp_socket& Socket) {
       FEXCore::ExecutableFileInfo MainFileId = {nullptr, filename_hash, fextl::string(Tmp, TmpLen)};
       fmt::print("Requested {}cache generation for {}\n", HasMultiblock ? "" : "nomb-", MainFileId.Filename);
 
-      // Update code maps
-      AggregateCodeMaps(MainFileId, HasMultiblock);
+      // Update code maps; any update necessitates an update of the corresponding cache
+      auto Binaries = AggregateCodeMaps(MainFileId, HasMultiblock);
 
-      // TODO: Implement
+      // Trigger offline-compile for each binary that needs it
+      for (const auto& [File, NeedsRefresh] : Binaries) {
+        if (NeedsRefresh != NeedsCacheRefresh::Yes) {
+          continue;
+        }
+
+        const auto BinaryName = (std::string)FEXCore::CodeMap::GetBaseFilename(File, !HasMultiblock);
+        fmt::println("Generating cache for {}", BinaryName);
+        int Status = RunOfflineCompiler(fmt::format("{}/ready/{}", CodeMapDirectory, BinaryName).c_str());
+        if (Status != 0) {
+          fmt::println("ERROR: Cache generation failed with status {}", Status);
+        }
+      }
 
       FEXServerClient::FEXServerResultPacket Res {
         .Header {