diff --git a/llvm/lib/Target/AMDGPU/SIMachineFunctionInfo.cpp b/llvm/lib/Target/AMDGPU/SIMachineFunctionInfo.cpp
--- a/llvm/lib/Target/AMDGPU/SIMachineFunctionInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/SIMachineFunctionInfo.cpp
@@ -145,9 +145,20 @@
     KernargSegmentPtr = true;
 
   if (ST.hasFlatAddressSpace() && isEntryFunction() && isAmdHsaOrMesa) {
+    auto hasNonSpillStackObjects = [&]() {
+      // Avoid expensive checking if there's no stack objects.
+      if (!HasStackObjects)
+        return false;
+      for (auto OI = FrameInfo.getObjectIndexBegin(),
+                OE = FrameInfo.getObjectIndexEnd(); OI != OE; ++OI)
+        if (!FrameInfo.isSpillSlotObjectIndex(OI))
+          return true;
+      // All stack objects are spill slots.
+      return false;
+    };
     // TODO: This could be refined a lot. The attribute is a poor way of
     // detecting calls that may require it before argument lowering.
-    if (HasStackObjects || F.hasFnAttribute("amdgpu-flat-scratch"))
+    if (hasNonSpillStackObjects() || F.hasFnAttribute("amdgpu-flat-scratch"))
       FlatScratchInit = true;
   }
 
diff --git a/llvm/test/CodeGen/AMDGPU/undefined-physreg-sgpr-spill.mir b/llvm/test/CodeGen/AMDGPU/undefined-physreg-sgpr-spill.mir
--- a/llvm/test/CodeGen/AMDGPU/undefined-physreg-sgpr-spill.mir
+++ b/llvm/test/CodeGen/AMDGPU/undefined-physreg-sgpr-spill.mir
@@ -41,7 +41,7 @@
 body:             |
   bb.0:
     successors: %bb.1, %bb.2
-    liveins: $vgpr0, $sgpr4_sgpr5
+    liveins: $vgpr0, $sgpr4_sgpr5, $sgpr8_sgpr9_sgpr10_sgpr11, $sgpr13
 
     $vgpr1_vgpr2 = COPY killed $sgpr4_sgpr5, implicit $exec
     $vgpr1 = GLOBAL_LOAD_UBYTE killed $vgpr1_vgpr2, 0, 0, 0, 0, implicit $exec :: (non-temporal dereferenceable invariant load 1 from `i1 addrspace(4)* undef`)
@@ -66,6 +66,7 @@
 
   bb.2:
     successors:
+    liveins: $sgpr8_sgpr9_sgpr10_sgpr11, $sgpr13
 
     $sgpr0_sgpr1 = SI_SPILL_S64_RESTORE %stack.0, implicit $exec, implicit $sgpr8_sgpr9_sgpr10_sgpr11, implicit $sgpr13, implicit-def dead $m0 :: (load 8 from %stack.0, align 4, addrspace 5)
     $exec = S_OR_B64 $exec, killed $sgpr0_sgpr1, implicit-def $scc
@@ -105,7 +106,7 @@
 body:             |
   bb.0:
     successors: %bb.1, %bb.2
-    liveins: $vgpr0, $sgpr4_sgpr5
+    liveins: $vgpr0, $sgpr4_sgpr5, $sgpr8_sgpr9_sgpr10_sgpr11, $sgpr13
 
     $vgpr1_vgpr2 = COPY killed $sgpr4_sgpr5, implicit $exec
     $vgpr1 = GLOBAL_LOAD_UBYTE killed $vgpr1_vgpr2, 0, 0, 0, 0, implicit $exec :: (non-temporal dereferenceable invariant load 1 from `i1 addrspace(4)* undef`)
@@ -130,6 +131,7 @@
 
   bb.2:
     successors:
+    liveins: $sgpr8_sgpr9_sgpr10_sgpr11, $sgpr13
 
     $sgpr0_sgpr1 = SI_SPILL_S64_RESTORE %stack.0, implicit $exec, implicit $sgpr8_sgpr9_sgpr10_sgpr11, implicit $sgpr13, implicit-def dead $m0 :: (load 8 from %stack.0, align 4, addrspace 5)
     $exec = S_OR_B64 $exec, killed $sgpr0_sgpr1, implicit-def $scc