Rollup merge of #101997 - cuviper:drop-legacy-pm, r=nikic

Remove support for legacy PM

This removes support for optimizing with LLVM's legacy pass manager, as well as the unstable `-Znew-llvm-pass-manager` option. We have been defaulting to the new PM since LLVM 13 (except for s390x that waited for 14), and LLVM 15 removed support altogether. The only place we still use the legacy PM is for writing the output file, just like `llc` does.

cc #74705
r? ``@nikic``

1 files changed, 2 insertions, 6 deletions

diff --git a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
index b2cfcf53c59..6f36281af23 100644
--- a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
@@ -12,7 +12,7 @@
 #include "llvm/Object/COFFImportFile.h"
 #include "llvm/Object/ObjectFile.h"
 #include "llvm/Pass.h"
-#include "llvm/Bitcode/BitcodeWriterPass.h"
+#include "llvm/Bitcode/BitcodeWriter.h"
 #include "llvm/Support/Signals.h"
 #include "llvm/ADT/Optional.h"
 
@@ -1670,11 +1670,7 @@ LLVMRustModuleBufferCreate(LLVMModuleRef M) {
   auto Ret = std::make_unique<LLVMRustModuleBuffer>();
   {
     raw_string_ostream OS(Ret->data);
-    {
-      legacy::PassManager PM;
-      PM.add(createBitcodeWriterPass(OS));
-      PM.run(*unwrap(M));
-    }
+    WriteBitcodeToFile(*unwrap(M), OS);
   }
   return Ret.release();
 }