3 files changed, 12 insertions, 14 deletions
diff --git a/compiler/rustc_llvm/Cargo.toml b/compiler/rustc_llvm/Cargo.toml
index cd352ce3d0f..0dfd1b13df5 100644
--- a/compiler/rustc_llvm/Cargo.toml
+++ b/compiler/rustc_llvm/Cargo.toml
@@ -11,7 +11,7 @@ libc = "0.2.73"
 [build-dependencies]
 # tidy-alphabetical-start
 # `cc` updates often break things, so we pin it here. Cargo enforces "max 1 semver-compat version
-# per crate", so if you change this, you need to also change it in `rustc_codegen_ssa`.
+# per crate", so if you change this, you need to also change it in `rustc_codegen_ssa` and `rustc_windows_rc`.
 cc = "=1.2.16"
 # tidy-alphabetical-end
 
diff --git a/compiler/rustc_llvm/build.rs b/compiler/rustc_llvm/build.rs
index d01f79dcade..9d21d0d22e3 100644
--- a/compiler/rustc_llvm/build.rs
+++ b/compiler/rustc_llvm/build.rs
@@ -174,10 +174,10 @@ fn main() {
 
     // Prevent critical warnings when we're compiling from rust-lang/rust CI,
     // except on MSVC, as the compiler throws warnings that are only reported
-    // for this platform. See https://github.com/rust-lang/rust/pull/145031#issuecomment-3162677202
-    // FIXME(llvm22): It looks like the specific problem code has been removed
-    // in https://github.com/llvm/llvm-project/commit/e8fc808bf8e78a3c80d1f8e293a92677b92366dd,
-    // retry msvc once we bump our LLVM version.
+    // for this platform. See https://github.com/rust-lang/rust/pull/145031#issuecomment-3162677202.
+    // Moreover, LLVM generally guarantees warning-freedom only when building with Clang, as other
+    // compilers have too many false positives. This is typically the case for MSVC, which throws
+    // many false-positive warnings. We keep it excluded, for these reasons.
     if std::env::var_os("CI").is_some() && !target.contains("msvc") {
         cfg.warnings_into_errors(true);
     }
@@ -254,7 +254,10 @@ fn main() {
         println!("cargo:rustc-link-lib=kstat");
     }
 
-    if (target.starts_with("arm") && !target.contains("freebsd") && !target.contains("ohos"))
+    if (target.starts_with("arm")
+        && !target.starts_with("arm64")
+        && !target.contains("freebsd")
+        && !target.contains("ohos"))
         || target.starts_with("mips-")
         || target.starts_with("mipsel-")
         || target.starts_with("powerpc-")
diff --git a/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp
index dd492325814..3bb1533c2fe 100644
--- a/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp
@@ -1568,12 +1568,11 @@ extern "C" bool LLVMRustPrepareThinLTOImport(const LLVMRustThinLTOData *Data,
   return true;
 }
 
-extern "C" LLVMRustThinLTOBuffer *
-LLVMRustThinLTOBufferCreate(LLVMModuleRef M, bool is_thin, bool emit_summary) {
+extern "C" LLVMRustThinLTOBuffer *LLVMRustThinLTOBufferCreate(LLVMModuleRef M,
+                                                              bool is_thin) {
   auto Ret = std::make_unique<LLVMRustThinLTOBuffer>();
   {
     auto OS = raw_string_ostream(Ret->data);
-    auto ThinLinkOS = raw_string_ostream(Ret->thin_link_data);
     {
       if (is_thin) {
         PassBuilder PB;
@@ -1587,11 +1586,7 @@ LLVMRustThinLTOBufferCreate(LLVMModuleRef M, bool is_thin, bool emit_summary) {
         PB.registerLoopAnalyses(LAM);
         PB.crossRegisterProxies(LAM, FAM, CGAM, MAM);
         ModulePassManager MPM;
-        // We only pass ThinLinkOS to be filled in if we want the summary,
-        // because otherwise LLVM does extra work and may double-emit some
-        // errors or warnings.
-        MPM.addPass(
-            ThinLTOBitcodeWriterPass(OS, emit_summary ? &ThinLinkOS : nullptr));
+        MPM.addPass(ThinLTOBitcodeWriterPass(OS, nullptr));
         MPM.run(*unwrap(M), MAM);
       } else {
         WriteBitcodeToFile(*unwrap(M), OS);