Index: lib/Target/X86/X86FrameLowering.cpp
===================================================================
--- lib/Target/X86/X86FrameLowering.cpp
+++ lib/Target/X86/X86FrameLowering.cpp
@@ -1550,6 +1550,7 @@
   }
   uint64_t SEHStackAllocAmt = NumBytes;
 
+  MachineBasicBlock::iterator FirstCSPop = MBBI;
   // Skip the callee-saved pop instructions.
   while (MBBI != MBB.begin()) {
     MachineBasicBlock::iterator PI = std::prev(MBBI);
@@ -1560,9 +1561,12 @@
         Opc != X86::DBG_VALUE && !PI->isTerminator())
       break;
 
+    if (Opc != X86::DBG_VALUE && !PI->isTerminator())
+      FirstCSPop = PI;
+
     --MBBI;
   }
-  MachineBasicBlock::iterator FirstCSPop = MBBI;
+  MBBI = FirstCSPop;
 
   if (TargetMBB) {
     // Fill EAX/RAX with the address of the target block.
Index: test/CodeGen/X86/frame-lowering-debug-intrinsic.ll
===================================================================
--- /dev/null
+++ test/CodeGen/X86/frame-lowering-debug-intrinsic.ll
@@ -0,0 +1,77 @@
+; Test ensuring debug intrinsics do not affect generated function prologue.
+;
+; RUN: llc  -mtriple=x86_64-unknown-unknown < %s | FileCheck %s
+
+define double @noDebug(double %a) {
+entry:
+  %call = tail call double @fmod(double %a, double 0x401921FB54442D18) #4
+  %call1 = tail call double @fabs(double %call) #3
+  %cmp = fcmp ult double %call1, 0x400921FB54442D18
+  br i1 %cmp, label %if.end, label %if.then
+
+if.then:                                          ; preds = %entry
+  %cmp2 = fcmp olt double %a, 0.000000e+00
+  %cond = select i1 %cmp2, double 0xC01921FB54442D18, double 0x401921FB54442D18
+  %sub = fsub double %call, %cond
+  br label %if.end
+
+if.end:                                           ; preds = %entry, %if.then
+  %w.0 = phi double [ %sub, %if.then ], [ %call, %entry ]
+  ret double %w.0
+}
+
+; CHECK noDebug:
+; CHECK: popq	%rax
+; CHECK: retq
+
+define double @withDebug(double %a) {
+entry:
+  %call = tail call double @fmod(double %a, double 0x401921FB54442D18) #4
+  %call1 = tail call double @fabs(double %call) #3
+  %cmp = fcmp ult double %call1, 0x400921FB54442D18
+  br i1 %cmp, label %if.end, label %if.then
+
+if.then:                                          ; preds = %entry
+  %cmp2 = fcmp olt double %a, 0.000000e+00
+  %cond = select i1 %cmp2, double 0xC01921FB54442D18, double 0x401921FB54442D18
+  %sub = fsub double %call, %cond
+  br label %if.end
+
+if.end:                                           ; preds = %entry, %if.then
+  %w.0 = phi double [ %sub, %if.then ], [ %call, %entry ]
+  tail call void @llvm.dbg.value(metadata double %w.0, i64 0, metadata !16, metadata !17), !dbg !20
+  ret double %w.0
+}
+
+; CHECK withDebug:
+; CHECK: popq	%rax
+; CHECK: ret
+
+declare double @fmod(double, double)
+
+declare double @fabs(double)
+
+declare void @llvm.dbg.value(metadata, i64, metadata, metadata)
+
+attributes #3 = { nounwind readnone }
+attributes #4 = { nounwind }
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, globals: !3)
+!1 = !DIFile(filename: "test.c", directory: "./")
+!2 = !{}
+!3 = !{!4, !7}
+!4 = distinct !DIGlobalVariable(name: "TWOPI", scope: !0, file: !1, line: 42, type: !5, isLocal: true, isDefinition: true)
+!5 = !DIDerivedType(tag: DW_TAG_const_type, baseType: !6)
+!6 = !DIBasicType(name: "double", size: 64, encoding: DW_ATE_float)
+!7 = distinct !DIGlobalVariable(name: "PI", scope: !0, file: !1, line: 38, type: !5, isLocal: true, isDefinition: true)
+!11 = distinct !DISubprogram(name: "anpm", scope: !1, file: !1, line: 208, type: !12, isLocal: false, isDefinition: true, scopeLine: 209, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !14)
+!12 = !DISubroutineType(types: !13)
+!13 = !{!6, !6}
+!14 = !{!15, !16}
+!15 = !DILocalVariable(name: "a", arg: 1, scope: !11, file: !1, line: 208, type: !6)
+!16 = !DILocalVariable(name: "w", scope: !11, file: !1, line: 210, type: !6)
+!17 = !DIExpression()
+!19 = !DILocation(line: 210, column: 16, scope: !11)
+!20 = !DILocation(line: 210, column: 12, scope: !11)
+!21 = !DILocation(line: 212, column: 9, scope: !22)
+!22 = distinct !DILexicalBlock(scope: !11, file: !1, line: 212, column: 9)