Prevent calls to __jit_debug_register_code from being optimized out.

Patch by Andrew MacPherson. I just tweaked the comment.

llvm-svn: 199350

1 files changed, 5 insertions, 1 deletions

diff --git a/llvm/lib/ExecutionEngine/RuntimeDyld/GDBRegistrar.cpp b/llvm/lib/ExecutionEngine/RuntimeDyld/GDBRegistrar.cpp
index 603c526d06e..60adc9b383d 100644
--- a/llvm/lib/ExecutionEngine/RuntimeDyld/GDBRegistrar.cpp
+++ b/llvm/lib/ExecutionEngine/RuntimeDyld/GDBRegistrar.cpp
@@ -47,7 +47,11 @@ extern "C" {
   struct jit_descriptor __jit_debug_descriptor = { 1, 0, 0, 0 };
 
   // Debuggers puts a breakpoint in this function.
-  LLVM_ATTRIBUTE_NOINLINE void __jit_debug_register_code() { }
+  LLVM_ATTRIBUTE_NOINLINE void __jit_debug_register_code() {
+    // The noinline and the asm prevent calls to this function from being
+    // optimized out.
+    asm volatile("":::"memory");
+  }
 
 }