introduce the VM_STATS environment variable to collect/dump compiler …

…stats

HACKING.rdoc

@@ -122,10 +122,13 @@ The following environment variables might help you debug easy bugs.
   builtin interpreter (generally used on cold paths).
 
 * VM_DUMP_IR: set it to any value to dump the LLVM IR on $stderr before the
-  interpreter quits.
+  program quits.
 
 * VM_VERIFY_IR: set it to any value to force a LLVM module verification before
-  the interpreter quits.
+  the program quits.
+
+* VM_STATS: set it to any value to collect then print compiler statistics
+  before the program quits.
 
 * VM_OPT_LEVEL: set it either to 0, 1, 2 or 3 to change the optimization level
   of the LLVM code generator.

vm.cpp

@@ -48,6 +48,7 @@
 # include <llvm/Intrinsics.h>
 # include <llvm/Bitcode/ReaderWriter.h>
 # include <llvm/LLVMContext.h>
+# include "llvm/ADT/Statistic.h"
 using namespace llvm;
 #endif // MACRUBY_STATIC
 
@@ -5188,6 +5189,8 @@ class_has_custom_resolver(Class klass)
 # include ".objs/kernel_data.c"
 #endif
 
+static bool vm_enable_stats = false;
+
 extern "C"
 void 
 Init_PreVM(void)
@@ -5202,6 +5205,11 @@ Init_PreVM(void)
     // To not corrupt stack pointer (essential for backtracing).
     llvm::NoFramePointerElim = true;
 
+    if (getenv("VM_STATS") != NULL) {
+	vm_enable_stats = true;
+	llvm::EnableStatistics();
+    }
+
     MemoryBuffer *mbuf = NULL;
     const char *kernel_file = getenv("VM_KERNEL_PATH");
     if (kernel_file != NULL) {
@@ -5560,6 +5568,10 @@ rb_vm_finalize(void)
 	rb_verify_module();
 	printf("IR verified!\n");
     }
+
+    if (vm_enable_stats) {
+	llvm::PrintStatistics();
+    }
 #endif
 
     // XXX: deleting the core is not safe at this point because there might be