diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index d83835a0f7b8a3..0c821b85c229a5 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -3754,7 +3754,12 @@ static void RenderDebugOptions(const ToolChain &TC, const Driver &D,
       Args.hasFlag(options::OPT_fsplit_dwarf_inlining,
                    options::OPT_fno_split_dwarf_inlining, false);
 
-  if (const Arg *A = Args.getLastArg(options::OPT_g_Group)) {
+  // Normally -gsplit-dwarf is only useful with -gN. For -gsplit-dwarf in the
+  // backend phase of a distributed ThinLTO which does object file generation
+  // and no IR generation, -gN should not be needed. So allow -gsplit-dwarf with
+  // either -gN or -fthinlto-index=.
+  if (Args.hasArg(options::OPT_g_Group) ||
+      Args.hasArg(options::OPT_fthinlto_index_EQ)) {
     Arg *SplitDWARFArg;
     DwarfFission = getDebugFissionKind(D, Args, SplitDWARFArg);
     if (DwarfFission != DwarfFissionKind::None &&
@@ -3762,7 +3767,8 @@ static void RenderDebugOptions(const ToolChain &TC, const Driver &D,
       DwarfFission = DwarfFissionKind::None;
       SplitDWARFInlining = false;
     }
-
+  }
+  if (const Arg *A = Args.getLastArg(options::OPT_g_Group)) {
     DebugInfoKind = codegenoptions::LimitedDebugInfo;
 
     // If the last option explicitly specified a debug-info level, use it.
diff --git a/clang/test/Driver/split-debug.c b/clang/test/Driver/split-debug.c
index de1258dcb13c99..2ce4ca980c3fcf 100644
--- a/clang/test/Driver/split-debug.c
+++ b/clang/test/Driver/split-debug.c
@@ -24,6 +24,14 @@
 /// -gsplit-dwarf is a no-op if no -g is specified.
 // RUN: %clang -### -c -target x86_64 -gsplit-dwarf %s 2>&1 | FileCheck %s --check-prefix=G0
 
+/// ... unless -fthinlto-index= is specified.
+// RUN: echo > %t.bc
+// RUN: %clang -### -c -target x86_64 -fthinlto-index=dummy -gsplit-dwarf %t.bc 2>&1 | FileCheck %s --check-prefix=THINLTO
+
+// THINLTO-NOT:  "-debug-info-kind=
+// THINLTO:      "-ggnu-pubnames"
+// THINLTO-SAME: "-split-dwarf-file" "{{.*}}.dwo" "-split-dwarf-output" "{{.*}}.dwo"
+
 /// -gno-split-dwarf disables debug fission.
 // RUN: %clang -### -c -target x86_64 -gsplit-dwarf -g -gno-split-dwarf %s 2>&1 | FileCheck %s --check-prefix=NOSPLIT
 // RUN: %clang -### -c -target x86_64 -gsplit-dwarf=single -g -gno-split-dwarf %s 2>&1 | FileCheck %s --check-prefix=NOSPLIT
diff --git a/llvm/include/llvm/ADT/SmallVector.h b/llvm/include/llvm/ADT/SmallVector.h
index ac445e556ba1f1..b9c30abcb579e3 100644
--- a/llvm/include/llvm/ADT/SmallVector.h
+++ b/llvm/include/llvm/ADT/SmallVector.h
@@ -545,11 +545,9 @@ class SmallVectorImpl : public SmallVectorTemplateBase<T> {
 private:
   template <bool ForOverwrite> void resizeImpl(size_type N) {
     if (N < this->size()) {
-      this->destroy_range(this->begin()+N, this->end());
-      this->set_size(N);
+      this->pop_back_n(this->size() - N);
     } else if (N > this->size()) {
-      if (this->capacity() < N)
-        this->grow(N);
+      this->reserve(N);
       for (auto I = this->end(), E = this->begin() + N; I != E; ++I)
         if (ForOverwrite)
           new (&*I) T;
@@ -570,8 +568,7 @@ class SmallVectorImpl : public SmallVectorTemplateBase<T> {
       return;
 
     if (N < this->size()) {
-      this->destroy_range(this->begin()+N, this->end());
-      this->set_size(N);
+      this->pop_back_n(this->size() - N);
       return;
     }
 
@@ -606,9 +603,7 @@ class SmallVectorImpl : public SmallVectorTemplateBase<T> {
   void append(in_iter in_start, in_iter in_end) {
     this->assertSafeToAddRange(in_start, in_end);
     size_type NumInputs = std::distance(in_start, in_end);
-    if (NumInputs > this->capacity() - this->size())
-      this->grow(this->size()+NumInputs);
-
+    this->reserve(this->size() + NumInputs);
     this->uninitialized_copy(in_start, in_end, this->end());
     this->set_size(this->size() + NumInputs);
   }
@@ -630,8 +625,7 @@ class SmallVectorImpl : public SmallVectorTemplateBase<T> {
   void assign(size_type NumElts, const T &Elt) {
     this->assertSafeToReferenceAfterResize(&Elt, 0);
     clear();
-    if (this->capacity() < NumElts)
-      this->grow(NumElts);
+    this->reserve(NumElts);
     this->set_size(NumElts);
     std::uninitialized_fill(this->begin(), this->end(), Elt);
   }
@@ -892,10 +886,8 @@ void SmallVectorImpl<T>::swap(SmallVectorImpl<T> &RHS) {
     std::swap(this->Capacity, RHS.Capacity);
     return;
   }
-  if (RHS.size() > this->capacity())
-    this->grow(RHS.size());
-  if (this->size() > RHS.capacity())
-    RHS.grow(this->size());
+  this->reserve(RHS.size());
+  RHS.reserve(this->size());
 
   // Swap the shared elements.
   size_t NumShared = this->size();
@@ -950,8 +942,7 @@ SmallVectorImpl<T> &SmallVectorImpl<T>::
   // FIXME: don't do this if they're efficiently moveable.
   if (this->capacity() < RHSSize) {
     // Destroy current elements.
-    this->destroy_range(this->begin(), this->end());
-    this->set_size(0);
+    this->clear();
     CurSize = 0;
     this->grow(RHSSize);
   } else if (CurSize) {
@@ -1010,8 +1001,7 @@ SmallVectorImpl<T> &SmallVectorImpl<T>::operator=(SmallVectorImpl<T> &&RHS) {
   // elements.
   if (this->capacity() < RHSSize) {
     // Destroy current elements.
-    this->destroy_range(this->begin(), this->end());
-    this->set_size(0);
+    this->clear();
     CurSize = 0;
     this->grow(RHSSize);
   } else if (CurSize) {
diff --git a/llvm/include/llvm/Config/llvm-config.h.cmake b/llvm/include/llvm/Config/llvm-config.h.cmake
index 7ee9f657c8a137..43107b086999d4 100644
--- a/llvm/include/llvm/Config/llvm-config.h.cmake
+++ b/llvm/include/llvm/Config/llvm-config.h.cmake
@@ -16,7 +16,7 @@
 
 /* Indicate that this is LLVM compiled from the amd-gfx branch. */
 #define LLVM_HAVE_BRANCH_AMD_GFX
-#define LLVM_MAIN_REVISION 376986
+#define LLVM_MAIN_REVISION 376990
 
 /* Define if LLVM_ENABLE_DUMP is enabled */
 #cmakedefine LLVM_ENABLE_DUMP