diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -3545,7 +3545,8 @@
     TrapBBs.resize(CheckHandlerID + 1);
   llvm::BasicBlock *&TrapBB = TrapBBs[CheckHandlerID];
 
-  if (!CGM.getCodeGenOpts().OptimizationLevel || !TrapBB) {
+  if (!CGM.getCodeGenOpts().OptimizationLevel || !TrapBB ||
+      CurFn->hasFnAttribute(llvm::Attribute::OptimizeNone)) {
     TrapBB = createBasicBlock("trap");
     Builder.CreateCondBr(Checked, Cont, TrapBB);
     EmitBlock(TrapBB);
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -5318,10 +5318,10 @@
   // Set CodeGen attributes that represent floating point environment.
   setLLVMFunctionFEnvAttributes(D, Fn);
 
+  SetLLVMFunctionAttributesForDefinition(D, Fn);
   CodeGenFunction(*this).GenerateCode(GD, Fn, FI);
 
   setNonAliasAttributes(GD, Fn);
-  SetLLVMFunctionAttributesForDefinition(D, Fn);
 
   if (const ConstructorAttr *CA = D->getAttr<ConstructorAttr>())
     AddGlobalCtor(Fn, CA->getPriority());
diff --git a/clang/test/CodeGen/ubsan-trap-debugloc.c b/clang/test/CodeGen/ubsan-trap-debugloc.c
--- a/clang/test/CodeGen/ubsan-trap-debugloc.c
+++ b/clang/test/CodeGen/ubsan-trap-debugloc.c
@@ -7,4 +7,16 @@
   a = a + 1;
 }
 
+void bar(volatile int a) __attribute__((optnone)) {
+  // CHECK: call void @llvm.ubsantrap(i8 0){{.*}} !dbg [[LOC2:![0-9]+]]
+  // CHECK: call void @llvm.ubsantrap(i8 0){{.*}} !dbg [[LOC3:![0-9]+]]
+  a = a + 1;
+  a = a + 1;
+}
+
+// With optimisations enabled the traps are merged and need to share a debug location
 // CHECK: [[LOC]] = !DILocation(line: 0
+
+// With optimisations disabled the traps are not merged and retain accurate debug locations
+// CHECK: [[LOC2]] = !DILocation(line: 13, column: 9
+// CHECK: [[LOC3]] = !DILocation(line: 14, column: 9