Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -10695,15 +10695,25 @@
   assert(gpu_archs.size() == 1 && "Exactly one GPU Arch required for ptxas.");
   const std::string& gpu_arch = gpu_archs[0];
 
-
   ArgStringList CmdArgs;
   CmdArgs.push_back(TC.getTriple().isArch64Bit() ? "-m64" : "-m32");
+  bool WantDebug = false;
+  Args.ClaimAllArgs(options::OPT_g_Group);
+  if (Arg *A = Args.getLastArg(options::OPT_g_Group))
+    WantDebug = !A->getOption().matches(options::OPT_g0) &&
+                !A->getOption().matches(options::OPT_ggdb0);
+  if (WantDebug) {
+    // ptxas does not accept -g option if optimization is enabled, so we ignore
+    // compiler's -O* options if we want debug info.
+    CmdArgs.push_back("-g");
+    CmdArgs.push_back("--dont-merge-basicblocks");
+    CmdArgs.push_back("--return-at-end");
+  } else if (Arg *A = Args.getLastArg(options::OPT_O_Group)) {
+    // Map the -O we received to -O{0,1,2,3}.
+    //
+    // TODO: Perhaps we should map host -O2 to ptxas -O3. -O3 is ptxas's
+    // default, so it may correspond more closely to the spirit of clang -O2.
 
-  // Map the -O we received to -O{0,1,2,3}.
-  //
-  // TODO: Perhaps we should map host -O2 to ptxas -O3. -O3 is ptxas's default,
-  // so it may correspond more closely to the spirit of clang -O2.
-  if (Arg *A = Args.getLastArg(options::OPT_O_Group)) {
     // -O3 seems like the least-bad option when -Osomething is specified to
     // clang but it isn't handled below.
     StringRef OOpt = "3";
@@ -10729,9 +10739,6 @@
     CmdArgs.push_back("-O0");
   }
 
-  // Don't bother passing -g to ptxas: It's enabled by default at -O0, and
-  // not supported at other optimization levels.
-
   CmdArgs.push_back("--gpu-name");
   CmdArgs.push_back(Args.MakeArgString(gpu_arch));
   CmdArgs.push_back("--output-file");
Index: test/Driver/cuda-external-tools.cu
===================================================================
--- test/Driver/cuda-external-tools.cu
+++ test/Driver/cuda-external-tools.cu
@@ -18,6 +18,14 @@
 // RUN: %clang -### -target x86_64-linux-gnu -Ofast -c %s 2>&1 \
 // RUN: | FileCheck -check-prefix ARCH64 -check-prefix SM20 -check-prefix OPT3 %s
 
+// With debugging enabled, ptxas should be run with with no ptxas optimizations.
+// RUN: %clang -### -target x86_64-linux-gnu -g -O2 -c %s 2>&1 \
+// RUN: | FileCheck -check-prefix ARCH64 -check-prefix SM20 -check-prefix DBG %s
+
+// Except when -g0 is passed which whould re-enable ptxas optimizations
+// RUN: %clang -### -target x86_64-linux-gnu -g0 -O2 -c %s 2>&1 \
+// RUN: | FileCheck -check-prefix ARCH64 -check-prefix SM20 -check-prefix OPT2 %s
+
 // Regular compile without -O.  This should result in us passing -O0 to ptxas.
 // RUN: %clang -### -target x86_64-linux-gnu -c %s 2>&1 \
 // RUN: | FileCheck -check-prefix ARCH64 -check-prefix SM20 -check-prefix OPT0 %s
@@ -59,9 +67,14 @@
 // ARCH64: "-m64"
 // ARCH32: "-m32"
 // OPT0: "-O0"
+// OPT0-NOT: "-g"
 // OPT1: "-O1"
+// OPT1-NOT: "-g"
 // OPT2: "-O2"
+// OPT2-NOT: "-g"
 // OPT3: "-O3"
+// OPT3-NOT: "-g"
+// DBG: "-g" "--dont-merge-basicblocks" "--return-at-end"
 // SM20: "--gpu-name" "sm_20"
 // SM35: "--gpu-name" "sm_35"
 // SM20: "--output-file" "[[CUBINFILE:[^"]*]]"