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.

4 files changed, 105 insertions, 3 deletions

diff --git a/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp
index ff2ec388a5f..f338b914c67 100644
--- a/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp
+++ b/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
diff --git a/tests/run-make/wasm-spurious-import/Makefile b/tests/run-make/wasm-builtins-import/Makefile
index ff9dfeac6d0..ff9dfeac6d0 100644
--- a/tests/run-make/wasm-spurious-import/Makefile
+++ b/tests/run-make/wasm-builtins-import/Makefile
diff --git a/tests/run-make/wasm-spurious-import/main.rs b/tests/run-make/wasm-builtins-import/main.rs
index fcbead5e28b..d7dbbe32ca4 100644
--- a/tests/run-make/wasm-spurious-import/main.rs
+++ b/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
 }
diff --git a/tests/run-make/wasm-spurious-import/verify.js b/tests/run-make/wasm-builtins-import/verify.js
index d3b2101b662..d3b2101b662 100644
--- a/tests/run-make/wasm-spurious-import/verify.js
+++ b/tests/run-make/wasm-builtins-import/verify.js