1 //===- Interpreter.cpp - Top-Level LLVM Interpreter Implementation --------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements the top-level functionality for the LLVM interpreter.
10 // This interpreter is designed to be a very simple, portable, inefficient
11 // interpreter.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "Interpreter.h"
16 #include "llvm/CodeGen/IntrinsicLowering.h"
17 #include "llvm/IR/DerivedTypes.h"
18 #include "llvm/IR/Module.h"
19 #include <cstring>
20 using namespace llvm;
21 
22 namespace {
23 
24 static struct RegisterInterp {
25   RegisterInterp() { Interpreter::Register(); }
26 } InterpRegistrator;
27 
28 }
29 
30 extern "C" void LLVMLinkInInterpreter() { }
31 
32 /// Create a new interpreter object.
33 ///
34 ExecutionEngine *Interpreter::create(std::unique_ptr<Module> M,
35                                      std::string *ErrStr) {
36   // Tell this Module to materialize everything and release the GVMaterializer.
37   if (Error Err = M->materializeAll()) {
38     std::string Msg;
39     handleAllErrors(std::move(Err), [&](ErrorInfoBase &EIB) {
40       Msg = EIB.message();
41     });
42     if (ErrStr)
43       *ErrStr = Msg;
44     // We got an error, just return 0
45     return nullptr;
46   }
47 
48   return new Interpreter(std::move(M));
49 }
50 
51 //===----------------------------------------------------------------------===//
52 // Interpreter ctor - Initialize stuff
53 //
54 Interpreter::Interpreter(std::unique_ptr<Module> M)
55     : ExecutionEngine(std::move(M)) {
56 
57   memset(&ExitValue.Untyped, 0, sizeof(ExitValue.Untyped));
58   // Initialize the "backend"
59   initializeExecutionEngine();
60   initializeExternalFunctions();
61   emitGlobals();
62 
63   IL = new IntrinsicLowering(getDataLayout());
64 }
65 
66 Interpreter::~Interpreter() {
67   delete IL;
68 }
69 
70 void Interpreter::runAtExitHandlers () {
71   while (!AtExitHandlers.empty()) {
72     callFunction(AtExitHandlers.back(), std::nullopt);
73     AtExitHandlers.pop_back();
74     run();
75   }
76 }
77 
78 /// run - Start execution with the specified function and arguments.
79 ///
80 GenericValue Interpreter::runFunction(Function *F,
81                                       ArrayRef<GenericValue> ArgValues) {
82   assert (F && "Function *F was null at entry to run()");
83 
84   // Try extra hard not to pass extra args to a function that isn't
85   // expecting them.  C programmers frequently bend the rules and
86   // declare main() with fewer parameters than it actually gets
87   // passed, and the interpreter barfs if you pass a function more
88   // parameters than it is declared to take. This does not attempt to
89   // take into account gratuitous differences in declared types,
90   // though.
91   const size_t ArgCount = F->getFunctionType()->getNumParams();
92   ArrayRef<GenericValue> ActualArgs =
93       ArgValues.slice(0, std::min(ArgValues.size(), ArgCount));
94 
95   // Set up the function call.
96   callFunction(F, ActualArgs);
97 
98   // Start executing the function.
99   run();
100 
101   return ExitValue;
102 }
103