[clang][deps] Remove dependency on llvm targets from lib DependencyScanning

[benlangmuir]

In d64eccf we split the object file reader from the writer and removed the dependency on clangCodeGen from the dependency scanner. However, we were still initializing all the llvm targets, which was needed for writing object file pcms but not reading them. This caused us to link more llvm target code than necessary. Shrinks clangd by nearly 50% for me.

rdar://144790713

[llvmbot]

@llvm/pr-subscribers-clang

Author: Ben Langmuir (benlangmuir)

Changes

In d64eccf we split the object file reader from the writer and removed the dependency on clangCodeGen from the dependency scanner. However, we were still initializing all the llvm targets, which was needed for writing object file pcms but not reading them. This caused us to link more llvm target code than necessary. Shrinks clangd by nearly 50% for me.

rdar://144790713

---

Full diff: https://github.com/llvm/llvm-project/pull/129774.diff

2 Files Affected:

• (modified) clang/lib/Tooling/DependencyScanning/CMakeLists.txt (-1)
• (modified) clang/lib/Tooling/DependencyScanning/DependencyScanningService.cpp (+1-8)

diff --git a/clang/lib/Tooling/DependencyScanning/CMakeLists.txt b/clang/lib/Tooling/DependencyScanning/CMakeLists.txt
index 66795b0be0baa..6b500a183bcfc 100644
--- a/clang/lib/Tooling/DependencyScanning/CMakeLists.txt
+++ b/clang/lib/Tooling/DependencyScanning/CMakeLists.txt
@@ -1,5 +1,4 @@
 set(LLVM_LINK_COMPONENTS
-  ${LLVM_TARGETS_TO_BUILD}
   Core
   Option
   Support
diff --git a/clang/lib/Tooling/DependencyScanning/DependencyScanningService.cpp b/clang/lib/Tooling/DependencyScanning/DependencyScanningService.cpp
index 4fb5977580497..96fe40c079c65 100644
--- a/clang/lib/Tooling/DependencyScanning/DependencyScanningService.cpp
+++ b/clang/lib/Tooling/DependencyScanning/DependencyScanningService.cpp
@@ -7,7 +7,6 @@
 //===----------------------------------------------------------------------===//
 
 #include "clang/Tooling/DependencyScanning/DependencyScanningService.h"
-#include "llvm/Support/TargetSelect.h"
 
 using namespace clang;
 using namespace tooling;
@@ -17,10 +16,4 @@ DependencyScanningService::DependencyScanningService(
     ScanningMode Mode, ScanningOutputFormat Format,
     ScanningOptimizations OptimizeArgs, bool EagerLoadModules, bool TraceVFS)
     : Mode(Mode), Format(Format), OptimizeArgs(OptimizeArgs),
-      EagerLoadModules(EagerLoadModules), TraceVFS(TraceVFS) {
-  // Initialize targets for object file support.
-  llvm::InitializeAllTargets();
-  llvm::InitializeAllTargetMCs();
-  llvm::InitializeAllAsmPrinters();
-  llvm::InitializeAllAsmParsers();
-}
+      EagerLoadModules(EagerLoadModules), TraceVFS(TraceVFS) {}

[jansvoboda11]

This is great, thank you!