Rollup merge of #138420 - zmodem:cfifunctionindex_fix, r=durin42

Adapt to LLVM dropping CfiFunctionIndex::begin()/end()

After llvm/llvm-project#130382, RustWrapper needs to call CfiFunctionIndex::symbols() instead.

Author: matthiaskrgr

compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp

@@ -1682,12 +1682,21 @@ extern "C" void LLVMRustComputeLTOCacheKey(RustStringRef KeyOut,
 #endif
 
   // Based on the 'InProcessThinBackend' constructor in LLVM
+#if LLVM_VERSION_GE(21, 0)
+  for (auto &Name : Data->Index.cfiFunctionDefs().symbols())
+    CfiFunctionDefs.insert(
+        GlobalValue::getGUID(GlobalValue::dropLLVMManglingEscape(Name)));
+  for (auto &Name : Data->Index.cfiFunctionDecls().symbols())
+    CfiFunctionDecls.insert(
+        GlobalValue::getGUID(GlobalValue::dropLLVMManglingEscape(Name)));
+#else
   for (auto &Name : Data->Index.cfiFunctionDefs())
     CfiFunctionDefs.insert(
         GlobalValue::getGUID(GlobalValue::dropLLVMManglingEscape(Name)));
   for (auto &Name : Data->Index.cfiFunctionDecls())
     CfiFunctionDecls.insert(
         GlobalValue::getGUID(GlobalValue::dropLLVMManglingEscape(Name)));
+#endif
 
 #if LLVM_VERSION_GE(20, 0)
   Key = llvm::computeLTOCacheKey(conf, Data->Index, ModId, ImportList,