fix non-enzyme builds

3 files changed, 14 insertions, 8 deletions

diff --git a/compiler/rustc_codegen_llvm/src/back/write.rs b/compiler/rustc_codegen_llvm/src/back/write.rs
index 4706744f353..155c07ff635 100644
--- a/compiler/rustc_codegen_llvm/src/back/write.rs
+++ b/compiler/rustc_codegen_llvm/src/back/write.rs
@@ -551,11 +551,12 @@ pub(crate) unsafe fn llvm_optimize(
     let vectorize_slp;
     let vectorize_loop;
 
+    let run_enzyme = cfg!(llvm_enzyme);
     // When we build rustc with enzyme/autodiff support, we want to postpone size-increasing
     // optimizations until after differentiation. FIXME(ZuseZ4): Before shipping on nightly,
     // we should make this more granular, or at least check that the user has at least one autodiff
     // call in their code, to justify altering the compilation pipeline.
-    if skip_size_increasing_opts && cfg!(llvm_enzyme) {
+    if skip_size_increasing_opts && run_enzyme {
         unroll_loops = false;
         vectorize_slp = false;
         vectorize_loop = false;
@@ -633,6 +634,7 @@ pub(crate) unsafe fn llvm_optimize(
             vectorize_loop,
             config.no_builtins,
             config.emit_lifetime_markers,
+            run_enzyme,
             sanitizer_options.as_ref(),
             pgo_gen_path.as_ref().map_or(std::ptr::null(), |s| s.as_ptr()),
             pgo_use_path.as_ref().map_or(std::ptr::null(), |s| s.as_ptr()),
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index cc7c5231aca..f2af400ce38 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -2346,6 +2346,7 @@ unsafe extern "C" {
         LoopVectorize: bool,
         DisableSimplifyLibCalls: bool,
         EmitLifetimeMarkers: bool,
+        RunEnzyme: bool,
         SanitizerOptions: Option<&SanitizerOptions>,
         PGOGenPath: *const c_char,
         PGOUsePath: *const c_char,
diff --git a/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp
index 0063f262c9b..0e591786d91 100644
--- a/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp
@@ -688,7 +688,8 @@ struct LLVMRustSanitizerOptions {
   bool SanitizeKernelAddressRecover;
 };
 
-extern "C" void registerEnzyme(llvm::PassBuilder &PB);
+// This symbol won't be available or used when Enzyme is not enabled
+extern "C" void registerEnzyme(llvm::PassBuilder &PB) __attribute__((weak));
 
 extern "C" LLVMRustResult LLVMRustOptimize(
     LLVMModuleRef ModuleRef, LLVMTargetMachineRef TMRef,
@@ -696,7 +697,7 @@ extern "C" LLVMRustResult LLVMRustOptimize(
     bool IsLinkerPluginLTO, bool NoPrepopulatePasses, bool VerifyIR,
     bool LintIR, bool UseThinLTOBuffers, bool MergeFunctions, bool UnrollLoops,
     bool SLPVectorize, bool LoopVectorize, bool DisableSimplifyLibCalls,
-    bool EmitLifetimeMarkers, LLVMRustSanitizerOptions *SanitizerOptions,
+    bool EmitLifetimeMarkers, bool RunEnzyme, LLVMRustSanitizerOptions *SanitizerOptions,
     const char *PGOGenPath, const char *PGOUsePath, bool InstrumentCoverage,
     const char *InstrProfileOutput, const char *PGOSampleUsePath,
     bool DebugInfoForProfiling, void *LlvmSelfProfiler,
@@ -1013,11 +1014,13 @@ extern "C" LLVMRustResult LLVMRustOptimize(
   }
 
   // now load "-enzyme" pass:
-  registerEnzyme(PB);
-  if (auto Err = PB.parsePassPipeline(MPM, "enzyme")) {
-    std::string ErrMsg = toString(std::move(Err));
-    LLVMRustSetLastError(ErrMsg.c_str());
-    return LLVMRustResult::Failure;
+  if (RunEnzyme) {
+    registerEnzyme(PB);
+    if (auto Err = PB.parsePassPipeline(MPM, "enzyme")) {
+      std::string ErrMsg = toString(std::move(Err));
+      LLVMRustSetLastError(ErrMsg.c_str());
+      return LLVMRustResult::Failure;
+    }
   }
 
   // Upgrade all calls to old intrinsics first.