[lld] [LLD][COFF] Introduce hybrid symbol table for EC input files on ARM64X (PR #119294)

[Jacek Caban via llvm-commits]

================
@@ -2519,54 +2529,56 @@ void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
   if (config->imageBase == uint64_t(-1))
     config->imageBase = getDefaultImageBase();
 
-  ctx.symtab.addSynthetic(mangle("__ImageBase"), nullptr);
-  if (config->machine == I386) {
-    ctx.symtab.addAbsolute("___safe_se_handler_table", 0);
-    ctx.symtab.addAbsolute("___safe_se_handler_count", 0);
-  }
-
-  ctx.symtab.addAbsolute(mangle("__guard_fids_count"), 0);
-  ctx.symtab.addAbsolute(mangle("__guard_fids_table"), 0);
-  ctx.symtab.addAbsolute(mangle("__guard_flags"), 0);
-  ctx.symtab.addAbsolute(mangle("__guard_iat_count"), 0);
-  ctx.symtab.addAbsolute(mangle("__guard_iat_table"), 0);
-  ctx.symtab.addAbsolute(mangle("__guard_longjmp_count"), 0);
-  ctx.symtab.addAbsolute(mangle("__guard_longjmp_table"), 0);
-  // Needed for MSVC 2017 15.5 CRT.
-  ctx.symtab.addAbsolute(mangle("__enclave_config"), 0);
-  // Needed for MSVC 2019 16.8 CRT.
-  ctx.symtab.addAbsolute(mangle("__guard_eh_cont_count"), 0);
-  ctx.symtab.addAbsolute(mangle("__guard_eh_cont_table"), 0);
-
-  if (isArm64EC(config->machine)) {
-    ctx.symtab.addAbsolute("__arm64x_extra_rfe_table", 0);
-    ctx.symtab.addAbsolute("__arm64x_extra_rfe_table_size", 0);
-    ctx.symtab.addAbsolute("__arm64x_redirection_metadata", 0);
-    ctx.symtab.addAbsolute("__arm64x_redirection_metadata_count", 0);
-    ctx.symtab.addAbsolute("__hybrid_auxiliary_delayload_iat_copy", 0);
-    ctx.symtab.addAbsolute("__hybrid_auxiliary_delayload_iat", 0);
-    ctx.symtab.addAbsolute("__hybrid_auxiliary_iat", 0);
-    ctx.symtab.addAbsolute("__hybrid_auxiliary_iat_copy", 0);
-    ctx.symtab.addAbsolute("__hybrid_code_map", 0);
-    ctx.symtab.addAbsolute("__hybrid_code_map_count", 0);
-    ctx.symtab.addAbsolute("__hybrid_image_info_bitfield", 0);
-    ctx.symtab.addAbsolute("__x64_code_ranges_to_entry_points", 0);
-    ctx.symtab.addAbsolute("__x64_code_ranges_to_entry_points_count", 0);
-    ctx.symtab.addSynthetic("__guard_check_icall_a64n_fptr", nullptr);
-    ctx.symtab.addSynthetic("__arm64x_native_entrypoint", nullptr);
-  }
-
-  if (config->pseudoRelocs) {
-    ctx.symtab.addAbsolute(mangle("__RUNTIME_PSEUDO_RELOC_LIST__"), 0);
-    ctx.symtab.addAbsolute(mangle("__RUNTIME_PSEUDO_RELOC_LIST_END__"), 0);
-  }
-  if (config->mingw) {
-    ctx.symtab.addAbsolute(mangle("__CTOR_LIST__"), 0);
-    ctx.symtab.addAbsolute(mangle("__DTOR_LIST__"), 0);
-  }
-  if (config->debug || config->buildIDHash != BuildIDHash::None)
-    if (ctx.symtab.findUnderscore("__buildid"))
-      ctx.symtab.addUndefined(mangle("__buildid"));
+  ctx.forEachSymtab([&](SymbolTable &symtab) {
+    symtab.addSynthetic(mangle("__ImageBase"), nullptr);
+    if (symtab.machine == I386) {
+      symtab.addAbsolute("___safe_se_handler_table", 0);
+      symtab.addAbsolute("___safe_se_handler_count", 0);
+    }
+
+    symtab.addAbsolute(mangle("__guard_fids_count"), 0);
+    symtab.addAbsolute(mangle("__guard_fids_table"), 0);
+    symtab.addAbsolute(mangle("__guard_flags"), 0);
+    symtab.addAbsolute(mangle("__guard_iat_count"), 0);
+    symtab.addAbsolute(mangle("__guard_iat_table"), 0);
+    symtab.addAbsolute(mangle("__guard_longjmp_count"), 0);
+    symtab.addAbsolute(mangle("__guard_longjmp_table"), 0);
+    // Needed for MSVC 2017 15.5 CRT.
+    symtab.addAbsolute(mangle("__enclave_config"), 0);
+    // Needed for MSVC 2019 16.8 CRT.
+    symtab.addAbsolute(mangle("__guard_eh_cont_count"), 0);
+    symtab.addAbsolute(mangle("__guard_eh_cont_table"), 0);
+
+    if (isArm64EC(ctx.config.machine)) {
----------------
cjacek wrote:

Yes, this should ultimately use `symtab.isEC()` instead. Changing it now would break CHPE data in the native load config. CHPE metadata should only exist in the EC namespace, but maintaining compatibility with existing tests requires linker support to copy it from the EC load config to the native one, as well as updates to the writer to correctly set those symbols in the appropriate namespace. This is implemented in [this commit](https://github.com/cjacek/llvm-project/commit/990b779ec6897fdd51dd5b1a13df085b390ccf2d).

https://github.com/llvm/llvm-project/pull/119294