Index: llvm/trunk/lib/Target/NVPTX/NVPTXPrologEpilogPass.cpp
===================================================================
--- llvm/trunk/lib/Target/NVPTX/NVPTXPrologEpilogPass.cpp
+++ llvm/trunk/lib/Target/NVPTX/NVPTXPrologEpilogPass.cpp
@@ -20,6 +20,7 @@
 #include "llvm/CodeGen/TargetFrameLowering.h"
 #include "llvm/CodeGen/TargetRegisterInfo.h"
 #include "llvm/CodeGen/TargetSubtargetInfo.h"
+#include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/Pass.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
@@ -60,6 +61,24 @@
       for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
         if (!MI.getOperand(i).isFI())
           continue;
+
+        // Frame indices in debug values are encoded in a target independent
+        // way with simply the frame index and offset rather than any
+        // target-specific addressing mode.
+        if (MI.isDebugValue()) {
+          assert(i == 0 && "Frame indices can only appear as the first "
+                           "operand of a DBG_VALUE machine instruction");
+          unsigned Reg;
+          int64_t Offset =
+              TFI.getFrameIndexReference(MF, MI.getOperand(0).getIndex(), Reg);
+          MI.getOperand(0).ChangeToRegister(Reg, /*isDef=*/false);
+          MI.getOperand(0).setIsDebug();
+          auto *DIExpr = DIExpression::prepend(MI.getDebugExpression(),
+                                               DIExpression::NoDeref, Offset);
+          MI.getOperand(3).setMetadata(DIExpr);
+          continue;
+        }
+
         TRI.eliminateFrameIndex(MI, 0, i, nullptr);
         Modified = true;
       }
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
@@ -0,0 +1,81 @@
+; RUN: llc -mtriple=nvptx64-nvidia-cuda < %s | FileCheck %s
+; Generated with -O1 from:
+; int f1();
+; void f2(int*);
+; int f3(int);
+;
+; int foo() {
+;   int i = 3;
+;   f3(i);
+;   i = 7;
+;   i = f1();
+;   f2(&i);
+;   return 0;
+; }
+;
+; Test that we generate valid debug info for optimized code,
+; 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 <- %
+
+; Function Attrs: nounwind ssp uwtable
+define i32 @foo() #0 !dbg !4 {
+entry:
+  %i = alloca i32, align 4
+  call void @llvm.dbg.value(metadata i32 3, metadata !10, metadata !DIExpression()), !dbg !15
+  %call = call i32 @f3(i32 3) #3, !dbg !16
+  call void @llvm.dbg.value(metadata i32 7, metadata !10, metadata !DIExpression()), !dbg !18
+  %call1 = call i32 (...) @f1() #3, !dbg !19
+  call void @llvm.dbg.value(metadata i32 %call1, metadata !10, metadata !DIExpression()), !dbg !19
+  store i32 %call1, i32* %i, align 4, !dbg !19, !tbaa !20
+  call void @llvm.dbg.value(metadata i32* %i, metadata !10, metadata !DIExpression(DW_OP_deref)), !dbg !24
+  call void @f2(i32* %i) #3, !dbg !24
+  ret i32 0, !dbg !25
+}
+
+declare i32 @f3(i32)
+
+declare i32 @f1(...)
+
+declare void @f2(i32*)
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.value(metadata, metadata, metadata) #2
+
+attributes #0 = { nounwind ssp uwtable }
+attributes #2 = { nounwind readnone }
+attributes #3 = { nounwind }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!11, !12}
+!llvm.ident = !{!13}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, producer: "clang version 3.5.0 ", isOptimized: true, emissionKind: FullDebug, file: !1, enums: !2, retainedTypes: !2, globals: !2, imports: !2)
+!1 = !DIFile(filename: "dbg-value-const-byref.c", directory: "")
+!2 = !{}
+!4 = distinct !DISubprogram(name: "foo", line: 5, isLocal: false, isDefinition: true, virtualIndex: 6, isOptimized: true, unit: !0, scopeLine: 5, file: !1, scope: !5, type: !6, retainedNodes: !9)
+!5 = !DIFile(filename: "dbg-value-const-byref.c", directory: "")
+!6 = !DISubroutineType(types: !7)
+!7 = !{!8}
+!8 = !DIBasicType(tag: DW_TAG_base_type, name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
+!9 = !{!10}
+!10 = !DILocalVariable(name: "i", line: 6, scope: !4, file: !5, type: !8)
+!11 = !{i32 2, !"Dwarf Version", i32 2}
+!12 = !{i32 1, !"Debug Info Version", i32 3}
+!13 = !{!"clang version 3.5.0 "}
+!14 = !{i32 3}
+!15 = !DILocation(line: 6, scope: !4)
+!16 = !DILocation(line: 7, scope: !4)
+!17 = !{i32 7}
+!18 = !DILocation(line: 8, scope: !4)
+!19 = !DILocation(line: 9, scope: !4)
+!20 = !{!21, !21, i64 0}
+!21 = !{!"int", !22, i64 0}
+!22 = !{!"omnipotent char", !23, i64 0}
+!23 = !{!"Simple C/C++ TBAA"}
+!24 = !DILocation(line: 10, scope: !4)
+!25 = !DILocation(line: 11, scope: !4)