diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 819ab9f047a5..87e886662f97 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -935,6 +935,18 @@ DbgVariable *DwarfDebug::createConcreteVariable(LexicalScope &Scope,
   return ConcreteVariables.back().get();
 }
 
+// Determine whether this DBG_VALUE is valid at the beginning of the function.
+static bool validAtEntry(const MachineInstr *MInsn) {
+  auto MBB = MInsn->getParent();
+  // Is it in the entry basic block?
+  if (!MBB->pred_empty())
+    return false;
+  for (MachineBasicBlock::const_reverse_iterator I(MInsn); I != MBB->rend(); ++I)
+    if (!(I->isDebugValue() || I->getFlag(MachineInstr::FrameSetup)))
+      return false;
+  return true;
+}
+
 // Find variables for each lexical scope.
 void DwarfDebug::collectVariableInfo(DwarfCompileUnit &TheCU,
                                      const DISubprogram *SP,
@@ -967,8 +979,11 @@ void DwarfDebug::collectVariableInfo(DwarfCompileUnit &TheCU,
     const MachineInstr *MInsn = Ranges.front().first;
     assert(MInsn->isDebugValue() && "History must begin with debug value");
 
-    // Check if the first DBG_VALUE is valid for the rest of the function.
-    if (Ranges.size() == 1 && Ranges.front().second == nullptr) {
+    // Check if there is a single DBG_VALUE, valid throughout the function.
+    // A single constant is also considered valid for the entire function.
+    if (Ranges.size() == 1 &&
+        (MInsn->getOperand(0).isImm() ||
+         (validAtEntry(MInsn) && Ranges.front().second == nullptr))) {
       RegVar->initializeDbgValue(MInsn);
       continue;
     }
diff --git a/llvm/test/DebugInfo/X86/PR26148.ll b/llvm/test/DebugInfo/X86/PR26148.ll
index b552508910c9..fe5567aba161 100644
--- a/llvm/test/DebugInfo/X86/PR26148.ll
+++ b/llvm/test/DebugInfo/X86/PR26148.ll
@@ -19,7 +19,7 @@
 ; AS in 26163, we expect two ranges (as opposed to one), the first one being zero sized
 ;
 ;
-; CHECK: 0x00000000: Beginning address offset: 0x0000000000000004
+; CHECK: 0x00000025: Beginning address offset: 0x0000000000000004
 ; CHECK:                Ending address offset: 0x0000000000000004
 ; CHECK:                 Location description: 10 03 55 93 04
 ; CHECK:             Beginning address offset: 0x0000000000000004
diff --git a/llvm/test/DebugInfo/X86/parameters.ll b/llvm/test/DebugInfo/X86/parameters.ll
index 1d71efc0719d..749d8ea8be16 100644
--- a/llvm/test/DebugInfo/X86/parameters.ll
+++ b/llvm/test/DebugInfo/X86/parameters.ll
@@ -25,15 +25,19 @@
 ; CHECK: debug_info contents
 ; 0x74 is DW_OP_breg4, showing that the parameter is accessed indirectly
 ; (with a zero offset) from the register parameter
-; CHECK: DW_AT_location{{.*}}(<0x0{{.}}> 74 00
+; CHECK: DW_AT_location [DW_FORM_data4]	([[F_LOC:0x[0-9]*]])
 ; CHECK-NOT: DW_TAG
 ; CHECK: DW_AT_name{{.*}} = "f"
-
+;
 ; CHECK: DW_AT_location{{.*}}([[G_LOC:0x[0-9]*]])
 ; CHECK-NOT: DW_TAG
 ; CHECK: DW_AT_name{{.*}} = "g"
+;
 ; CHECK: debug_loc contents
-; CHECK-NEXT: [[G_LOC]]: Beginning
+; CHECK:         [[F_LOC]]: Beginning
+; CHECK-NEXT:               Ending
+; CHECK-NEXT: Location description: 74 00
+; CHECK:         [[G_LOC]]: Beginning
 ; CHECK-NEXT:               Ending
 ; CHECK-NEXT: Location description: 74 00
 
diff --git a/llvm/test/DebugInfo/X86/pieces-2.ll b/llvm/test/DebugInfo/X86/pieces-2.ll
index 8a43f452d32b..225d49a3f863 100644
--- a/llvm/test/DebugInfo/X86/pieces-2.ll
+++ b/llvm/test/DebugInfo/X86/pieces-2.ll
@@ -17,10 +17,15 @@
 ;
 ;
 ; CHECK: DW_TAG_variable [4]
-;                                                  rax, piece 0x00000004
-; CHECK-NEXT: DW_AT_location [DW_FORM_block1]{{.*}}50 93 04
+; CHECK-NEXT:   DW_AT_location [DW_FORM_data4]        ([[LOC:.*]])
 ; CHECK-NEXT:  DW_AT_name {{.*}}"i1"
 ;
+; CHECK: .debug_loc
+; CHECK: [[LOC]]: Beginning address offset: 0x0000000000000004
+; CHECK-NEXT:        Ending address offset: 0x0000000000000005
+;                                           rax, piece 0x00000004
+; CHECK-NEXT:         Location description: 50 93 04
+;
 ; ModuleID = '/Volumes/Data/llvm/test/DebugInfo/X86/sroasplit-1.ll'
 target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-apple-macosx10.9.0"
diff --git a/llvm/test/DebugInfo/X86/pieces-3.ll b/llvm/test/DebugInfo/X86/pieces-3.ll
index 7a93e393b25f..1a36672c30f6 100644
--- a/llvm/test/DebugInfo/X86/pieces-3.ll
+++ b/llvm/test/DebugInfo/X86/pieces-3.ll
@@ -16,19 +16,22 @@
 ;    }
 ;
 ; CHECK: DW_TAG_formal_parameter [3]
-; CHECK-NEXT:   DW_AT_location [DW_FORM_data4]        ([[LOC:.*]])
+; CHECK-NEXT:   DW_AT_location [DW_FORM_data4]        ([[LOC1:.*]])
 ; CHECK-NEXT:   DW_AT_name {{.*}}"outer"
 ; CHECK: DW_TAG_variable
-;                                                 rsi, piece 0x00000004
-; CHECK-NEXT:   DW_AT_location [DW_FORM_block1]       {{.*}} 54 93 04
+; CHECK-NEXT:   DW_AT_location [DW_FORM_data4]        ([[LOC2:.*]])
 ; CHECK-NEXT:   "i1"
 ;
 ; CHECK: .debug_loc
-; CHECK: [[LOC]]:
-; CHECK: Beginning address offset: 0x0000000000000000
-; CHECK:    Ending address offset: 0x0000000000000008
-; rdi, piece 0x00000008, piece 0x00000004, rsi, piece 0x00000004
-; CHECK: Location description: 55 93 08 93 04 54 93 04 
+; CHECK: [[LOC1]]: Beginning address offset: 0x0000000000000000
+; CHECK:              Ending address offset: 0x0000000000000008
+;             rdi, piece 0x00000008, piece 0x00000004, rsi, piece 0x00000004
+; CHECK-NEXT: Location description: 55 93 08 93 04 54 93 04
+; CHECK: [[LOC2]]: Beginning address offset: 0x0000000000000004
+; CHECK-NEXT:         Ending address offset: 0x0000000000000008
+;                                     rsi, piece 0x00000004
+; CHECK-NEXT:   Location description: 54 93 04
+
 ;
 ; ModuleID = '/Volumes/Data/llvm/test/DebugInfo/X86/sroasplit-2.ll'
 target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
diff --git a/llvm/test/DebugInfo/X86/reference-argument.ll b/llvm/test/DebugInfo/X86/reference-argument.ll
index 9433b8785311..fcbbac9a0335 100644
--- a/llvm/test/DebugInfo/X86/reference-argument.ll
+++ b/llvm/test/DebugInfo/X86/reference-argument.ll
@@ -1,8 +1,9 @@
-; RUN: llc -mtriple=x86_64-apple-macosx10.9.0 -filetype=obj -O0 < %s | llvm-dwarfdump -debug-dump=info - | FileCheck %s
+; RUN: llc -mtriple=x86_64-apple-macosx10.9.0 -filetype=obj -O0 < %s | llvm-dwarfdump -debug-dump=all - | FileCheck %s
 ; ModuleID = 'aggregate-indirect-arg.cpp'
 ; extracted from debuginfo-tests/aggregate-indirect-arg.cpp
 
 ; v should be a pointer.
+; CHECK:  .debug_info contents:
 ; CHECK:   DW_TAG_subprogram
 ; CHECK:     DW_AT_specification {{.*}} "_ZN1A3fooE4SVal"
 ; CHECK-NOT: DW_TAG_subprogram
@@ -10,9 +11,11 @@
 ; CHECK:       DW_AT_name {{.*}} "this"
 ; CHECK-NOT:   DW_TAG_subprogram
 ; CHECK:     DW_TAG_formal_parameter
-;                                                    rsi+0
-; CHECK-NEXT:  DW_AT_location [DW_FORM_block1]      (<0x02> 74 00{{ *}})
+; CHECK-NEXT:  DW_AT_location [DW_FORM_data4]	(0x00000000)
 ; CHECK-NEXT:  DW_AT_name {{.*}} "v"
+; CHECK: .debug_loc contents:
+;                                rsi+0
+; CHECK:   Location description: 74 00
 
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
 target triple = "x86_64-apple-macosx10.9.0"
diff --git a/llvm/test/DebugInfo/X86/single-dbg_value.ll b/llvm/test/DebugInfo/X86/single-dbg_value.ll
new file mode 100644
index 000000000000..68a37eb0df03
--- /dev/null
+++ b/llvm/test/DebugInfo/X86/single-dbg_value.ll
@@ -0,0 +1,71 @@
+; RUN: %llc_dwarf -stop-after=livedebugvalues -o /dev/null %s 2>&1 \
+; RUN:   | FileCheck %s --check-prefix=SANITY
+; RUN: %llc_dwarf -march=x86-64 -o - %s -filetype=obj \
+; RUN:   | llvm-dwarfdump -debug-dump=all - | FileCheck %s
+;
+; CHECK: .debug_info contents:
+; CHECK: DW_TAG_variable
+; CHECK-NEXT:   DW_AT_location [DW_FORM_data4]
+; CHECK-NEXT:   DW_AT_name{{.*}}"a"
+; CHECK: .debug_loc contents:
+;                               rax, piece 0x00000004
+; CHECK:  Location description: 50 93 04
+; SANITY: DBG_VALUE
+; SANITY-NOT: DBG_VALUE
+; ModuleID = 'test.ll'
+; Compiled with -O:
+;   void h(int);
+;   int g();
+;   void f() {
+;     h(0);
+;     int a = g();
+;     h(a);
+;   }
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx"
+
+; Function Attrs: nounwind ssp uwtable
+define void @f() #0 !dbg !4 {
+entry:
+  tail call void @h(i32 0) #2, !dbg !14
+  %call = tail call i32 (...) @g() #2, !dbg !15
+  tail call void @llvm.dbg.value(metadata i32 %call, i64 0, metadata !8, metadata !16), !dbg !17
+  tail call void @h(i32 %call) #2, !dbg !18
+  ret void, !dbg !19
+}
+
+declare void @h(i32)
+
+declare i32 @g(...)
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.value(metadata, i64, metadata, metadata) #1
+
+attributes #0 = { nounwind ssp uwtable "no-frame-pointer-elim"="true" }
+attributes #1 = { nounwind readnone }
+attributes #2 = { nounwind }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!10, !11, !12}
+!llvm.ident = !{!13}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 3.9.0 ", isOptimized: true, runtimeVersion: 0, emissionKind: 1, enums: !2, subprograms: !3)
+!1 = !DIFile(filename: "test.c", directory: "/Volumes/Data/llvm")
+!2 = !{}
+!3 = !{!4}
+!4 = distinct !DISubprogram(name: "f", scope: !1, file: !1, line: 3, type: !5, isLocal: false, isDefinition: true, scopeLine: 3, isOptimized: true, variables: !7)
+!5 = !DISubroutineType(types: !6)
+!6 = !{null}
+!7 = !{!8}
+!8 = !DILocalVariable(name: "a", scope: !4, file: !1, line: 5, type: !9)
+!9 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
+!10 = !{i32 2, !"Dwarf Version", i32 2}
+!11 = !{i32 2, !"Debug Info Version", i32 3}
+!12 = !{i32 1, !"PIC Level", i32 2}
+!13 = !{!"clang version 3.9.0 "}
+!14 = !DILocation(line: 4, column: 3, scope: !4)
+!15 = !DILocation(line: 5, column: 11, scope: !4)
+!16 = !DIExpression()
+!17 = !DILocation(line: 5, column: 7, scope: !4)
+!18 = !DILocation(line: 6, column: 3, scope: !4)
+!19 = !DILocation(line: 7, column: 1, scope: !4)
diff --git a/llvm/test/DebugInfo/X86/subregisters.ll b/llvm/test/DebugInfo/X86/subregisters.ll
index 9dcb09f0869d..a6d356f658ff 100644
--- a/llvm/test/DebugInfo/X86/subregisters.ll
+++ b/llvm/test/DebugInfo/X86/subregisters.ll
@@ -6,8 +6,13 @@
 ;
 ; rdar://problem/16015314
 ;
-; CHECK:  DW_AT_location [DW_FORM_block1]       (<0x03> 54 93 04 )
-; CHECK:  DW_AT_name [DW_FORM_strp]{{.*}} "a"
+; CHECK:  .debug_info contents:
+; CHECK:  DW_TAG_variable
+; CHECK-NEXT:  DW_AT_location [DW_FORM_data4]	(0x00000000)
+; CHECK-NEXT:  DW_AT_name [DW_FORM_strp]{{.*}} "a"
+; CHECK: .debug_loc contents:
+;                                    rsi, piece 0x00000004
+; CHECK:       Location description: 54 93 04 
 ;
 ; struct bar {
 ;   int a;