Add flag to lli to enable debugging of IR when used with MCJIT.

- warn users when -debug-ir is used with old JIT engine (only partial debug
  info is available) 

For example, to debug an IR file with GDB (that supports JIT registration), do:

$ gdb --args lli -use-mcjit -debug-ir testcase.ll
(gdb) break main
(gdb) run
<Process continues to lli main>
(gdb) continue
<Process continues to testcase.ll main()
(gdb) step
<Now stepping through the LLVM IR in testcase.ll>

llvm-svn: 185197

1 files changed, 16 insertions, 0 deletions

diff --git a/llvm/tools/lli/lli.cpp b/llvm/tools/lli/lli.cpp
index 031f945abae..8d74b2326d7 100644
--- a/llvm/tools/lli/lli.cpp
+++ b/llvm/tools/lli/lli.cpp
@@ -45,6 +45,7 @@
 #include "llvm/Support/SourceMgr.h"
 #include "llvm/Support/TargetSelect.h"
 #include "llvm/Support/raw_ostream.h"
+#include "llvm/Transforms/Instrumentation.h"
 #include <cerrno>
 
 #ifdef __CYGWIN__
@@ -71,6 +72,10 @@ namespace {
     "use-mcjit", cl::desc("Enable use of the MC-based JIT (if available)"),
     cl::init(false));
 
+  cl::opt<bool> DebugIR(
+    "debug-ir", cl::desc("Generate debug information to allow debugging IR."),
+    cl::init(false));
+
   // The MCJIT supports building for a target address space separate from
   // the JIT compilation process. Use a forked process and a copying
   // memory manager with IPC to execute using this functionality.
@@ -321,6 +326,17 @@ int main(int argc, char **argv, char * const *envp) {
     }
   }
 
+  if (DebugIR) {
+    if (!UseMCJIT) {
+      errs() << "warning: -debug-ir used without -use-mcjit. Only partial debug"
+        << " information will be emitted by the non-MC JIT engine. To see full"
+        << " source debug information, enable the flag '-use-mcjit'.\n";
+
+    }
+    ModulePass *DebugIRPass = createDebugIRPass();
+    DebugIRPass->runOnModule(*Mod);
+  }
+
   EngineBuilder builder(Mod);
   builder.setMArch(MArch);
   builder.setMCPU(MCPU);