Add PreservedSymbols from LLVM to LTO.

When building with LTO, builtin functions that are defined but whose calls have not been inserted yet, get internalized.
We need to prevent these symbols from being internalized at LTO time.

Refer to https://reviews.llvm.org/D49434.

compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp

@@ -1120,6 +1120,102 @@ extern "C" void LLVMRustPrintPasses() {
   PB.printPassNames(outs());
 }
 
+// from https://github.com/llvm/llvm-project/blob/7021182d6b43de9488ab70de626192ce70b3a4a6/llvm/lib/Object/IRSymtab.cpp#L48-L57
+static const char *PreservedLibcallSymbols[] = {
+#define HANDLE_LIBCALL(code, name) name,
+#include "llvm/IR/RuntimeLibcalls.def"
+#undef HANDLE_LIBCALL
+  // RuntimeLibcalls.def missing symbols.
+  "__ctzsi2",
+  "__ctzdi2",
+  "__ctzti2",
+  "__ffssi2",
+  "__ffsdi2",
+  "__ffsti2",
+  "__paritysi2",
+  "__paritydi2",
+  "__parityti2",
+  "__popcountsi2",
+  "__popcountdi2",
+  "__popcountti2",
+  "__bswapsi2",
+  "__bswapdi2",
+  "__negti2",
+  "__udivmoddi4",
+  "__udivmodti4",
+  "__udivmodsi4",
+  "__divmodsi4",
+  "__divmoddi4",
+  "__divmodti4",
+  "__absvsi2",
+  "__absvdi2",
+  "__absvti2",
+  "__negvsi2",
+  "__negvdi2",
+  "__negvti2",
+  "__addvsi3",
+  "__addvdi3",
+  "__addvti3",
+  "__subvsi3",
+  "__subvdi3",
+  "__subvti3",
+  "__mulvsi3",
+  "__mulvdi3",
+  "__mulvti3",
+  "__cmpdi2",
+  "__cmpti2",
+  "__ucmpdi2",
+  "__ucmpti2",
+  "__mulsc3",
+  "__muldc3",
+  "__mulxc3",
+  "__multc3",
+  "__divsc3",
+  "__divdc3",
+  "__divxc3",
+  "__divtc3",
+  "__clear_cache",
+  "__enable_execute_stack",
+  "__gcc_personality_v0",
+  "__eprintf",
+  "__emutls_get_address",
+  "__trampoline_setup",
+  "__addsf3vfp",
+  "__adddf3vfp",
+  "__divsf3vfp",
+  "__divdf3vfp",
+  "__eqsf2vfp",
+  "__eqdf2vfp",
+  "__extendsfdf2vfp",
+  "__fixdfsivfp",
+  "__fixsfsivfp",
+  "__fixunssfsivfp",
+  "__fixunsdfsivfp",
+  "__floatsidfvfp",
+  "__floatsisfvfp",
+  "__floatunssidfvfp",
+  "__floatunssisfvfp",
+  "__gedf2vfp",
+  "__gesf2vfp",
+  "__gtdf2vfp",
+  "__gtsf2vfp",
+  "__ledf2vfp",
+  "__lesf2vfp",
+  "__ltdf2vfp",
+  "__ltsf2vfp",
+  "__muldf3vfp",
+  "__mulsf3vfp",
+  "__nedf2vfp",
+  "__negdf2vfp",
+  "__negsf2vfp",
+  "__negsf2vfp",
+  "__subdf3vfp",
+  "__subsf3vfp",
+  "__truncdfsf2vfp",
+  "__unorddf2vfp",
+  "__unordsf2vfp",
+};
+
 extern "C" void LLVMRustRunRestrictionPass(LLVMModuleRef M, char **Symbols,
                                            size_t Len) {
   auto PreserveFunctions = [=](const GlobalValue &GV) {
@@ -1135,7 +1231,7 @@ extern "C" void LLVMRustRunRestrictionPass(LLVMModuleRef M, char **Symbols,
         return true;
       }
     }
-    return false;
+    return llvm::is_contained(PreservedLibcallSymbols, GV.getName());
   };
 
   internalizeModule(*unwrap(M), PreserveFunctions);
@@ -1293,6 +1389,12 @@ LLVMRustCreateThinLTOData(LLVMRustThinLTOModule *modules,
     auto GUID = GlobalValue::getGUID(preserved_symbols[i]);
     Ret->GUIDPreservedSymbols.insert(GUID);
   }
+  for (int i = 0; i < sizeof(PreservedLibcallSymbols) / sizeof(PreservedLibcallSymbols[0]); i++) {
+    if (auto *PreservedLibcallSymbol = PreservedLibcallSymbols[i]) {
+      auto GUID = GlobalValue::getGUID(PreservedLibcallSymbol);
+      Ret->GUIDPreservedSymbols.insert(GUID);
+    }
+  }
 
   // Collect the import/export lists for all modules from the call-graph in the
   // combined index

tests/run-make/wasm-spurious-import/main.rs → tests/run-make/wasm-builtins-import/main.rs

@@ -8,7 +8,7 @@ fn my_panic(_info: &core::panic::PanicInfo) -> ! {
 
 #[no_mangle]
 pub fn multer(a: i128, b: i128) -> i128 {
-    // Trigger usage of the __multi3 compiler intrinsic which then leads to an imported
-    // panic function in case of a bug. We verify that no imports exist in our verifier.
+    // Trigger usage of the __multi3 compiler intrinsic which then leads to an imported function
+    // such as panic or __multi3 in case of a bug. We verify that no imports exist in our verifier.
     a * b
 }