[ORC] Add an OrcV2 ResourceTracker / Removable-code example.

Author: lhames

llvm/examples/OrcV2Examples/CMakeLists.txt

@@ -11,3 +11,4 @@ add_subdirectory(LLJITWithThinLTOSummaries)
 add_subdirectory(OrcV2CBindingsAddObjectFile)
 add_subdirectory(OrcV2CBindingsBasicUsage)
 add_subdirectory(OrcV2CBindingsReflectProcessSymbols)
+add_subdirectory(OrcV2CBindingsRemovableCode)

llvm/examples/OrcV2Examples/OrcV2CBindingsRemovableCode/CMakeLists.txt

@@ -0,0 +1,15 @@
+set(LLVM_LINK_COMPONENTS
+  Core
+  ExecutionEngine
+  IRReader
+  JITLink
+  MC
+  OrcJIT
+  Support
+  Target
+  nativecodegen
+  )
+
+add_llvm_example(OrcV2CBindingsRemovableCode
+  OrcV2CBindingsRemovableCode.c
+  )

llvm/examples/OrcV2Examples/OrcV2CBindingsRemovableCode/OrcV2CBindingsRemovableCode.c

@@ -0,0 +1,176 @@
+//===-------- BasicOrcV2CBindings.c - Basic OrcV2 C Bindings Demo ---------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm-c/Core.h"
+#include "llvm-c/Error.h"
+#include "llvm-c/Initialization.h"
+#include "llvm-c/Orc.h"
+#include "llvm-c/Support.h"
+#include "llvm-c/Target.h"
+
+#include <stdio.h>
+
+int handleError(LLVMErrorRef Err) {
+  char *ErrMsg = LLVMGetErrorMessage(Err);
+  fprintf(stderr, "Error: %s\n", ErrMsg);
+  LLVMDisposeErrorMessage(ErrMsg);
+  return 1;
+}
+
+LLVMOrcThreadSafeModuleRef createDemoModule() {
+  // Create a new ThreadSafeContext and underlying LLVMContext.
+  LLVMOrcThreadSafeContextRef TSCtx = LLVMOrcCreateNewThreadSafeContext();
+
+  // Get a reference to the underlying LLVMContext.
+  LLVMContextRef Ctx = LLVMOrcThreadSafeContextGetContext(TSCtx);
+
+  // Create a new LLVM module.
+  LLVMModuleRef M = LLVMModuleCreateWithNameInContext("demo", Ctx);
+
+  // Add a "sum" function":
+  //  - Create the function type and function instance.
+  LLVMTypeRef ParamTypes[] = {LLVMInt32Type(), LLVMInt32Type()};
+  LLVMTypeRef SumFunctionType =
+      LLVMFunctionType(LLVMInt32Type(), ParamTypes, 2, 0);
+  LLVMValueRef SumFunction = LLVMAddFunction(M, "sum", SumFunctionType);
+
+  //  - Add a basic block to the function.
+  LLVMBasicBlockRef EntryBB = LLVMAppendBasicBlock(SumFunction, "entry");
+
+  //  - Add an IR builder and point it at the end of the basic block.
+  LLVMBuilderRef Builder = LLVMCreateBuilder();
+  LLVMPositionBuilderAtEnd(Builder, EntryBB);
+
+  //  - Get the two function arguments and use them co construct an "add"
+  //    instruction.
+  LLVMValueRef SumArg0 = LLVMGetParam(SumFunction, 0);
+  LLVMValueRef SumArg1 = LLVMGetParam(SumFunction, 1);
+  LLVMValueRef Result = LLVMBuildAdd(Builder, SumArg0, SumArg1, "result");
+
+  //  - Build the return instruction.
+  LLVMBuildRet(Builder, Result);
+
+  // Our demo module is now complete. Wrap it and our ThreadSafeContext in a
+  // ThreadSafeModule.
+  LLVMOrcThreadSafeModuleRef TSM = LLVMOrcCreateNewThreadSafeModule(M, TSCtx);
+
+  // Dispose of our local ThreadSafeContext value. The underlying LLVMContext
+  // will be kept alive by our ThreadSafeModule, TSM.
+  LLVMOrcDisposeThreadSafeContext(TSCtx);
+
+  // Return the result.
+  return TSM;
+}
+
+int main(int argc, char *argv[]) {
+
+  int MainResult = 0;
+
+  // Parse command line arguments and initialize LLVM Core.
+  LLVMParseCommandLineOptions(argc, (const char **)argv, "");
+  LLVMInitializeCore(LLVMGetGlobalPassRegistry());
+
+  // Initialize native target codegen and asm printer.
+  LLVMInitializeNativeTarget();
+  LLVMInitializeNativeAsmPrinter();
+
+  // Create the JIT instance.
+  LLVMOrcLLJITRef J;
+  {
+    LLVMErrorRef Err;
+    if ((Err = LLVMOrcCreateLLJIT(&J, 0))) {
+      MainResult = handleError(Err);
+      goto llvm_shutdown;
+    }
+  }
+
+  // Create our demo module.
+  LLVMOrcThreadSafeModuleRef TSM = createDemoModule();
+  LLVMOrcResourceTrackerRef RT;
+
+  // Add our demo module to the JIT.
+  {
+    LLVMOrcJITDylibRef MainJD = LLVMOrcLLJITGetMainJITDylib(J);
+    RT = LLVMOrcJITDylibCreateResourceTracker(MainJD);
+    LLVMErrorRef Err;
+    if ((Err = LLVMOrcLLJITAddLLVMIRModuleWithRT(J, RT, TSM))) {
+      // If adding the ThreadSafeModule fails then we need to clean it up
+      // ourselves. If adding it succeeds the JIT will manage the memory.
+      LLVMOrcDisposeThreadSafeModule(TSM);
+      MainResult = handleError(Err);
+      goto jit_cleanup;
+    }
+  }
+
+  // Look up the address of our demo entry point.
+  printf("Looking up before removal...\n");
+  LLVMOrcJITTargetAddress SumAddr;
+  {
+    LLVMErrorRef Err;
+    if ((Err = LLVMOrcLLJITLookup(J, &SumAddr, "sum"))) {
+      MainResult = handleError(Err);
+      goto jit_cleanup;
+    }
+  }
+
+  // If we made it here then everything succeeded. Execute our JIT'd code.
+  int32_t (*Sum)(int32_t, int32_t) = (int32_t(*)(int32_t, int32_t))SumAddr;
+  int32_t Result = Sum(1, 2);
+
+  // Print the result.
+  printf("1 + 2 = %i\n", Result);
+
+  // Remove the code.
+  {
+    LLVMErrorRef Err;
+    if ((Err = LLVMOrcResourceTrackerRemove(RT))) {
+      MainResult = handleError(Err);
+      goto jit_cleanup;
+    }
+  }
+
+  // Attempt a second lookup. Here we expect an error as the code and symbols
+  // should have been removed.
+  printf("Attempting to remove code / symbols...\n");
+  {
+    LLVMOrcJITTargetAddress ThrowAwayAddress;
+    LLVMErrorRef Err = LLVMOrcLLJITLookup(J, &ThrowAwayAddress, "sum");
+    if (Err) {
+      printf("Received error as expected:\n");
+      handleError(Err);
+    } else {
+      printf("Failure: Second lookup should have generated an error.\n");
+      MainResult = 1;
+    }
+  }
+
+jit_cleanup:
+  // Destroy our JIT instance. This will clean up any memory that the JIT has
+  // taken ownership of. This operation is non-trivial (e.g. it may need to
+  // JIT static destructors) and may also fail. In that case we want to render
+  // the error to stderr, but not overwrite any existing return value.
+
+  printf("Releasing resource tracker...\n");
+  LLVMOrcReleaseResourceTracker(RT);
+
+  printf("Destroying LLJIT instance and exiting.\n");
+  {
+    LLVMErrorRef Err;
+    if ((Err = LLVMOrcDisposeLLJIT(J))) {
+      int NewFailureResult = handleError(Err);
+      if (MainResult == 0)
+        MainResult = NewFailureResult;
+    }
+  }
+
+llvm_shutdown:
+  // Shut down LLVM.
+  LLVMShutdown();
+
+  return MainResult;
+}