[MCJIT] Fix PR20656 by teaching MCJIT to honor ExecutionEngine's global mapping.

This is important for users of the C API who can't supply custom symbol
resolvers yet.

llvm-svn: 243589

Author: lhames

llvm/lib/ExecutionEngine/ExecutionEngine.cpp

@@ -189,10 +189,17 @@ uint64_t ExecutionEngineState::RemoveMapping(StringRef Name) {
 }
 
 std::string ExecutionEngine::getMangledName(const GlobalValue *GV) {
+  assert(GV->hasName() && "Global must have name.");
+
   MutexGuard locked(lock);
-  Mangler Mang;
   SmallString<128> FullName;
-  Mang.getNameWithPrefix(FullName, GV, false);
+
+  const DataLayout &DL =
+    GV->getParent()->getDataLayout().isDefault()
+      ? getDataLayout()
+      : GV->getParent()->getDataLayout();
+
+  Mangler::getNameWithPrefix(FullName, GV->getName(), DL);
   return FullName.str();
 }
 

llvm/lib/ExecutionEngine/MCJIT/MCJIT.cpp

@@ -270,6 +270,12 @@ void MCJIT::finalizeModule(Module *M) {
 RuntimeDyld::SymbolInfo MCJIT::findExistingSymbol(const std::string &Name) {
   SmallString<128> FullName;
   Mangler::getNameWithPrefix(FullName, Name, getDataLayout());
+
+  if (void *Addr = getPointerToGlobalIfAvailable(FullName))
+    return RuntimeDyld::SymbolInfo(static_cast<uint64_t>(
+                                     reinterpret_cast<uintptr_t>(Addr)),
+                                   JITSymbolFlags::Exported);
+
   return Dyld.getSymbol(FullName);
 }
 

llvm/unittests/ExecutionEngine/MCJIT/MCJITCAPITest.cpp

@@ -488,3 +488,36 @@ TEST_F(MCJITCAPITest, yield) {
   EXPECT_TRUE(didCallYield);
 }
 
+static int localTestFunc() {
+  return 42;
+}
+
+TEST_F(MCJITCAPITest, addGlobalMapping) {
+  SKIP_UNSUPPORTED_PLATFORM;
+
+  Module = LLVMModuleCreateWithName("testModule");
+  LLVMTypeRef FunctionType = LLVMFunctionType(LLVMInt32Type(), NULL, 0, 0);
+  LLVMValueRef MappedFn = LLVMAddFunction(Module, "mapped_fn", FunctionType);
+
+  Function = LLVMAddFunction(Module, "test_fn", FunctionType);
+  LLVMBasicBlockRef Entry = LLVMAppendBasicBlock(Function, "");
+  LLVMBuilderRef Builder = LLVMCreateBuilder();
+  LLVMPositionBuilderAtEnd(Builder, Entry);
+  LLVMValueRef RetVal = LLVMBuildCall(Builder, MappedFn, NULL, 0, "");
+  LLVMBuildRet(Builder, RetVal);
+
+  LLVMVerifyModule(Module, LLVMAbortProcessAction, &Error);
+  LLVMDisposeMessage(Error);
+
+  buildMCJITOptions();
+  buildMCJITEngine();
+
+  LLVMAddGlobalMapping(Engine, MappedFn, reinterpret_cast<void*>(&localTestFunc));
+
+  buildAndRunPasses();
+
+  uint64_t raw = LLVMGetFunctionAddress(Engine, "test_fn");
+  int (*usable)() = (int (*)()) raw;
+
+  EXPECT_EQ(42, usable());
+}