# --- T2-COPYRIGHT-BEGIN ---
# t2/package/*/rustc/hotfix-llvm23-assign-guid.patch
# Copyright (C) 2026 The T2 SDE Project
# SPDX-License-Identifier: GPL-2.0 or patched project license
# --- T2-COPYRIGHT-END ---

Subject: [PATCH] rustc_llvm: run AssignGUIDPass before writing ThinLTO bitcode on LLVM 23

LLVM 23 stores each global's GUID as !unique_id metadata, assigned by
the new AssignGUIDPass (llvm/Transforms/Utils/AssignGUID.h), and
GlobalValue::getGUID() no longer computes it from the name for a
definition. Upstream added the pass to addRequiredLTOPreLinkPasses(),
but rustc duplicates that list by hand (CanonicalizeAliases +
NameAnonGlobal) for the -Copt-level=0 / -Cembed-bitcode path, and
LLVMRustModuleSerialize runs ThinLTOBitcodeWriterPass on its own.

Without the pass, ModuleSummaryAnalysis records definitions under a
garbage GUID while the bitcode writer looks them up with
getGUIDOrFallback() (the name's MD5), so every crate built with
embed-bitcode dies with

  rustc-LLVM ERROR: expected function definition _RINv... to have an
  associated value info.

The optimised ThinLTO pre-link pipelines already get the pass from
LLVM; it is idempotent, so running it again is harmless.

---
--- a/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp	2026-09-19 17:10:43.533342019 +0200
+++ b/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp	2026-09-19 17:10:43.555836853 +0200
@@ -58,6 +58,9 @@
 
 // Conditional includes prevent clang-format from fully sorting the list,
 // so if any are needed, keep them separate down here.
+#if LLVM_VERSION_GE(23, 0)
+#include "llvm/Transforms/Utils/AssignGUID.h"
+#endif
 
 using namespace llvm;
 
@@ -925,6 +928,11 @@
   if (NeedThinLTOBufferPasses) {
     MPM.addPass(CanonicalizeAliasesPass());
     MPM.addPass(NameAnonGlobalPass());
+#if LLVM_VERSION_GE(23, 0)
+    // LLVM 23 stores GUIDs as metadata and no longer computes them on the
+    // fly; the summary written by ThinLTOBitcodeWriterPass needs them.
+    MPM.addPass(AssignGUIDPass());
+#endif
   }
   // For `-Copt-level=0`, and the pre-link fat/thin LTO stages.
   if (ThinLTOBufferRef && *ThinLTOBufferRef == nullptr) {
@@ -1464,6 +1472,9 @@
         PB.registerLoopAnalyses(LAM);
         PB.crossRegisterProxies(LAM, FAM, CGAM, MAM);
         ModulePassManager MPM;
+#if LLVM_VERSION_GE(23, 0)
+        MPM.addPass(AssignGUIDPass());
+#endif
         MPM.addPass(ThinLTOBitcodeWriterPass(OS, nullptr));
         MPM.run(*unwrap(M), MAM);
       } else {