Index: include/clang/Basic/Sanitizers.def
===================================================================
--- include/clang/Basic/Sanitizers.def
+++ include/clang/Basic/Sanitizers.def
@@ -37,6 +37,8 @@
 #define SANITIZER_GROUP(NAME, ID, ALIAS)
 #endif
 
+// Debug mode for sanitizers
+SANITIZER("debug-mode", DebugMode)
 
 // AddressSanitizer
 SANITIZER("address", Address)
Index: lib/CodeGen/CGExpr.cpp
===================================================================
--- lib/CodeGen/CGExpr.cpp
+++ lib/CodeGen/CGExpr.cpp
@@ -27,6 +27,7 @@
 #include "llvm/ADT/Hashing.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/IR/DataLayout.h"
+#include "llvm/IR/InlineAsm.h"
 #include "llvm/IR/Intrinsics.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/MDBuilder.h"
@@ -2535,9 +2536,25 @@
 void CodeGenFunction::EmitTrapCheck(llvm::Value *Checked) {
   llvm::BasicBlock *Cont = createBasicBlock("cont");
 
-  // If we're optimizing, collapse all calls to trap down to just one per
-  // function to save on code size.
-  if (!CGM.getCodeGenOpts().OptimizationLevel || !TrapBB) {
+  // Collapsing all calls to trap down to one per function makes debugging
+  // these issues much more difficult. Eliminating this optimization 
+  // for debugging purposes.
+  // RE: Bug: 25682
+  if(SanOpts.has(SanitizerKind::DebugMode)) {
+      llvm::InlineAsm *EmptyAsm = llvm::InlineAsm::get(llvm::FunctionType::get(CGM.VoidTy, false), 
+						       StringRef(""), StringRef(""), true);
+      TrapBB = createBasicBlock("trap");
+      Builder.CreateCondBr(Checked, Cont, TrapBB);
+      EmitBlock(TrapBB);
+      llvm::CallInst *TrapCall = EmitTrapCall(llvm::Intrinsic::trap);
+      TrapCall->setDoesNotReturn();
+      TrapCall->setDoesNotThrow();
+      Builder.CreateUnreachable();
+      //this stops the trap calls from being merged at the end of the function
+      Builder.CreateCall(EmptyAsm, {});
+  } else if(!CGM.getCodeGenOpts().OptimizationLevel || !TrapBB) {
+    // If we're optimizing, collapse all calls to trap down to just one per
+    // function to save on code size.
     TrapBB = createBasicBlock("trap");
     Builder.CreateCondBr(Checked, Cont, TrapBB);
     EmitBlock(TrapBB);
@@ -2548,7 +2565,7 @@
   } else {
     Builder.CreateCondBr(Checked, Cont, TrapBB);
   }
-
+  
   EmitBlock(Cont);
 }
 
Index: lib/Driver/ToolChain.cpp
===================================================================
--- lib/Driver/ToolChain.cpp
+++ lib/Driver/ToolChain.cpp
@@ -657,7 +657,8 @@
   // platform dependent.
   using namespace SanitizerKind;
   SanitizerMask Res = (Undefined & ~Vptr & ~Function) | (CFI & ~CFIICall) |
-                      CFICastStrict | UnsignedIntegerOverflow | LocalBounds;
+                      CFICastStrict | UnsignedIntegerOverflow | LocalBounds |
+                      DebugMode;
   if (getTriple().getArch() == llvm::Triple::x86 ||
       getTriple().getArch() == llvm::Triple::x86_64)
     Res |= CFIICall;