[ORC] Add a runAsMain utility function to ExecutionUtils.

The runAsMain function takes a pointer to a function with a standard C main
signature, int(*)(int, char*[]), and invokes it using the given arguments and
program name. The arguments are copied into writable temporary storage as
required by the C and C++ specifications, so runAsMain safe to use when calling
main functions that modify their arguments in-place.

This patch also uses the new runAsMain function to replace hand-rolled versions
in lli, llvm-jitlink, and the SpeculativeJIT example.

1 files changed, 26 insertions, 0 deletions

diff --git a/llvm/lib/ExecutionEngine/Orc/ExecutionUtils.cpp b/llvm/lib/ExecutionEngine/Orc/ExecutionUtils.cpp
index 4a3482242db..0a3fef207ac 100644
--- a/llvm/lib/ExecutionEngine/Orc/ExecutionUtils.cpp
+++ b/llvm/lib/ExecutionEngine/Orc/ExecutionUtils.cpp
@@ -19,6 +19,32 @@
 namespace llvm {
 namespace orc {
 
+int runAsMain(int (*Main)(int, char *[]), ArrayRef<std::string> Args,
+              Optional<StringRef> ProgramName) {
+  std::vector<std::unique_ptr<char[]>> ArgVStorage;
+  std::vector<char *> ArgV;
+
+  ArgVStorage.reserve(Args.size() + (ProgramName ? 1 : 0));
+  ArgV.reserve(Args.size() + 1 + (ProgramName ? 1 : 0));
+
+  if (ProgramName) {
+    ArgVStorage.push_back(std::make_unique<char[]>(ProgramName->size() + 1));
+    llvm::copy(*ProgramName, &ArgVStorage.back()[0]);
+    ArgVStorage.back()[ProgramName->size()] = '\0';
+    ArgV.push_back(ArgVStorage.back().get());
+  }
+
+  for (auto &Arg : Args) {
+    ArgVStorage.push_back(std::make_unique<char[]>(Arg.size() + 1));
+    llvm::copy(Arg, &ArgVStorage.back()[0]);
+    ArgVStorage.back()[Arg.size()] = '\0';
+    ArgV.push_back(ArgVStorage.back().get());
+  }
+  ArgV.push_back(nullptr);
+
+  return Main(Args.size(), ArgV.data());
+}
+
 CtorDtorIterator::CtorDtorIterator(const GlobalVariable *GV, bool End)
   : InitList(
       GV ? dyn_cast_or_null<ConstantArray>(GV->getInitializer()) : nullptr),