Index: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -5320,6 +5320,21 @@
       return nullptr;
     }
 
+    // If the Value is a frame index, we can create a FrameIndex debug value
+    // without relying on the DAG at all.
+    if (const AllocaInst *AI = dyn_cast<AllocaInst>(V)) {
+      auto SI = FuncInfo.StaticAllocaMap.find(AI);
+      if (SI != FuncInfo.StaticAllocaMap.end()) {
+        auto SDV =
+            DAG.getFrameIndexDbgValue(Variable, Expression, SI->second,
+                                      /*IsIndirect*/ false, dl, SDNodeOrder);
+        // Do not attach the SDNodeDbgValue to an SDNode: this variable location
+        // is still available even if the SDNode gets optimized out.
+        DAG.AddDbgValue(SDV, nullptr, false);
+        return nullptr;
+      }
+    }
+
     // Do not use getValue() in here; we don't want to generate code at
     // this point if it hasn't been done yet.
     SDValue N = NodeMap[V];
Index: llvm/trunk/test/DebugInfo/NVPTX/dbg-value-const-byref.ll
===================================================================
--- llvm/trunk/test/DebugInfo/NVPTX/dbg-value-const-byref.ll
+++ llvm/trunk/test/DebugInfo/NVPTX/dbg-value-const-byref.ll
@@ -17,10 +17,10 @@
 ; particularly variables that are described as constants and passed
 ; by reference.
 ;
-; CHECK: DEBUG_VALUE: foo:i <- [DW_OP_deref] $vrdepot
 ; CHECK: DEBUG_VALUE: foo:i <- 3
 ; CHECK: DEBUG_VALUE: foo:i <- 7
 ; CHECK: DEBUG_VALUE: foo:i <- %
+; CHECK: DEBUG_VALUE: foo:i <- [DW_OP_deref] $vrdepot
 
 ; Function Attrs: nounwind ssp uwtable
 define i32 @foo() #0 !dbg !4 {
Index: llvm/trunk/test/DebugInfo/X86/dbg-value-frame-index-2.ll
===================================================================
--- llvm/trunk/test/DebugInfo/X86/dbg-value-frame-index-2.ll
+++ llvm/trunk/test/DebugInfo/X86/dbg-value-frame-index-2.ll
@@ -0,0 +1,79 @@
+; RUN: llc -start-after=codegenprepare -stop-before=expand-isel-pseudos < %s -o - | FileCheck %s
+
+; Test that stack frame dbg.values are lowered to DBG_VALUEs, in blocks that
+; are local to the alloca, and elsewhere. Differs from dbg-value-frame-index.ll
+; because this test does not result in the frame-index being in a vreg,
+; instead it's exclusively referred to by memory operands of instructions.
+;
+; Additionally test that we don't re-order with constant values -- both are
+; independent of the order the instructions get lowered, but should not
+; interleave.
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-unknown"
+
+declare void @dud()
+
+; CHECK: [[BARVAR:![0-9]+]] = !DILocalVariable(name: "bar",
+
+define i32 @foo() !dbg !6 {
+; CHECK-LABEL: body
+
+; CHECK:      DBG_VALUE 0, $noreg, [[BARVAR]]
+; CHECK-NEXT: MOV32mi %[[STACKLOC:[a-zA-Z0-9\.]+]], 1, $noreg
+; CHECK-NEXT: DBG_VALUE %[[STACKLOC]], $noreg, [[BARVAR]]
+
+  %p1 = alloca i32
+  call void @llvm.dbg.value(metadata i32 *null, metadata !17, metadata !DIExpression()), !dbg !18
+  store i32 0, i32 *%p1
+  call void @llvm.dbg.value(metadata i32 *%p1, metadata !17, metadata !DIExpression()), !dbg !18
+  br label %foo
+
+foo:
+
+; CHECK-LABEL: bb.1.foo
+; CHECK:      DBG_VALUE %[[STACKLOC]], $noreg, [[BARVAR]]
+
+  call void @dud()
+  call void @llvm.dbg.value(metadata i32 *%p1, metadata !17, metadata !DIExpression()), !dbg !18
+  br label %bar
+
+bar:
+
+; CHECK-LABEL: bb.2.bar
+; CHECK:      DBG_VALUE %[[STACKLOC]], $noreg, [[BARVAR]]
+; CHECK-NEXT: ADJCALLSTACKDOWN
+; CHECK-NEXT: CALL
+; CHECK-NEXT: ADJCALLSTACKUP
+; CHECK-NEXT: DBG_VALUE 0, $noreg, [[BARVAR]]
+  call void @llvm.dbg.value(metadata i32 *%p1, metadata !17, metadata !DIExpression()), !dbg !18
+  call void @dud()
+  call void @llvm.dbg.value(metadata i32 *null, metadata !17, metadata !DIExpression()), !dbg !18
+  %loaded = load i32, i32 *%p1
+  ret i32 %loaded, !dbg !19
+}
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.value(metadata, metadata, metadata) #6
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4}
+!llvm.ident = !{!5}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1, producer: "", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !2, globals: !2)
+!1 = !DIFile(filename: "a.c", directory: "b")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{!""}
+!6 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 13, type: !7, isLocal: false, isDefinition: true, scopeLine: 14, isOptimized: false, unit: !0, retainedNodes: !2)
+!7 = !DISubroutineType(types: !8)
+!8 = !{!140}
+!140 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!15 = !{!16}
+!16 = !DISubrange(count: 5)
+!17 = !DILocalVariable(name: "bar", scope: !6, line: 13, type: !140)
+!18 = !DILocation(line: 13, column: 23, scope: !6)
+!19 = !DILocation(line: 15, column: 5, scope: !6)
+!20 = !DILocation(line: 16, column: 1, scope: !6)
+!21 = !DILocalVariable(name: "baz", scope: !6, line: 13, type: !140)