Index: lib/Transforms/IPO/SampleProfile.cpp
===================================================================
--- lib/Transforms/IPO/SampleProfile.cpp
+++ lib/Transforms/IPO/SampleProfile.cpp
@@ -122,6 +122,7 @@
   void buildEdges(Function &F);
   bool propagateThroughEdges(Function &F);
   void computeDominanceAndLoopInfo(Function &F);
+  unsigned getOffset(unsigned L, unsigned H) const;
 
   /// \brief Map basic blocks to their computed weights.
   ///
@@ -174,6 +175,17 @@
 };
 }
 
+/// \brief Returns the offset of lineno \p L to head_lineno \p H
+///
+/// \param L  Lineno
+/// \param H  Header lineno of the function
+///
+/// \returns offset to the header lineno. 16 bits are used to represent offset.
+/// We assume that a single function will not exceed 65535 LOC.
+unsigned SampleProfileLoader::getOffset(unsigned L, unsigned H) const {
+  return (L - H) & 0xffff;
+}
+
 /// \brief Print the weight of edge \p E on stream \p OS.
 ///
 /// \param OS  Stream to emit the output to.
@@ -229,11 +241,9 @@
   const DILocation *DIL = DLoc;
   unsigned Lineno = DLoc.getLine();
   unsigned HeaderLineno = DIL->getScope()->getSubprogram()->getLine();
-  if (Lineno < HeaderLineno)
-    return std::error_code();
 
-  ErrorOr<uint64_t> R =
-      FS->findSamplesAt(Lineno - HeaderLineno, DIL->getDiscriminator());
+  ErrorOr<uint64_t> R = FS->findSamplesAt(getOffset(Lineno, HeaderLineno),
+                                          DIL->getDiscriminator());
   if (R)
     DEBUG(dbgs() << "    " << Lineno << "." << DIL->getDiscriminator() << ":"
                  << Inst << " (line offset: " << Lineno - HeaderLineno << "."
@@ -308,7 +318,7 @@
     return nullptr;
   }
   DISubprogram *SP = DIL->getScope()->getSubprogram();
-  if (!SP || DIL->getLine() < SP->getLine())
+  if (!SP)
     return nullptr;
 
   Function *CalleeFunc = Inst.getCalledFunction();
@@ -321,8 +331,9 @@
   if (FS == nullptr)
     return nullptr;
 
-  return FS->findFunctionSamplesAt(CallsiteLocation(
-      DIL->getLine() - SP->getLine(), DIL->getDiscriminator(), CalleeName));
+  return FS->findFunctionSamplesAt(
+      CallsiteLocation(getOffset(DIL->getLine(), SP->getLine()),
+                       DIL->getDiscriminator(), CalleeName));
 }
 
 /// \brief Get the FunctionSamples for an instruction.
@@ -345,10 +356,10 @@
   for (const DILocation *DIL = Inst.getDebugLoc(); DIL;
        DIL = DIL->getInlinedAt()) {
     DISubprogram *SP = DIL->getScope()->getSubprogram();
-    if (!SP || DIL->getLine() < SP->getLine())
+    if (!SP)
       return nullptr;
     if (!CalleeName.empty()) {
-      S.push_back(CallsiteLocation(DIL->getLine() - SP->getLine(),
+      S.push_back(CallsiteLocation(getOffset(DIL->getLine(), SP->getLine()),
                                    DIL->getDiscriminator(), CalleeName));
     }
     CalleeName = SP->getLinkageName();
Index: test/Transforms/SampleProfile/Inputs/offset.prof
===================================================================
--- /dev/null
+++ test/Transforms/SampleProfile/Inputs/offset.prof
@@ -0,0 +1,4 @@
+_Z3fooi:300:1
+ 65532: 1000
+ 65533: 10
+ 65535: 990
Index: test/Transforms/SampleProfile/offset.ll
===================================================================
--- /dev/null
+++ test/Transforms/SampleProfile/offset.ll
@@ -0,0 +1,82 @@
+; RUN: opt < %s -sample-profile -sample-profile-file=%S/Inputs/offset.prof | opt -analyze -branch-prob | FileCheck %s
+
+; Original C++ code for this test case:
+;
+; a.cc:
+; #1
+; #2
+; #3
+; #4
+; #5 int foo(int a) {
+; #6 #include "a.b"
+; #7}
+;
+; a.b:
+; #1 if (a > 0) {
+; #2   return 10;
+; #3 } else {
+; #4   return 20;
+; #5 }
+
+; Function Attrs: nounwind uwtable
+define i32 @_Z3fooi(i32 %a) #0 {
+entry:
+  %retval = alloca i32, align 4
+  %a.addr = alloca i32, align 4
+  store i32 %a, i32* %a.addr, align 4
+  call void @llvm.dbg.declare(metadata i32* %a.addr, metadata !11, metadata !12), !dbg !13
+  %0 = load i32, i32* %a.addr, align 4, !dbg !14
+  %cmp = icmp sgt i32 %0, 0, !dbg !18
+  br i1 %cmp, label %if.then, label %if.else, !dbg !19
+; CHECK: edge entry -> if.then probability is 0x0147ae14 / 0x80000000 = 1.00%
+; CHECK: edge entry -> if.else probability is 0x7eb851ec / 0x80000000 = 99.00% [HOT edge]
+
+if.then:                                          ; preds = %entry
+  store i32 10, i32* %retval, align 4, !dbg !20
+  br label %return, !dbg !20
+
+if.else:                                          ; preds = %entry
+  store i32 20, i32* %retval, align 4, !dbg !22
+  br label %return, !dbg !22
+
+return:                                           ; preds = %if.else, %if.then
+  %1 = load i32, i32* %retval, align 4, !dbg !24
+  ret i32 %1, !dbg !24
+}
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+
+attributes #0 = { nounwind uwtable "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { nounwind readnone }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!8, !9}
+!llvm.ident = !{!10}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 3.8.0 (trunk 250750)", isOptimized: false, runtimeVersion: 0, emissionKind: 1, enums: !2, subprograms: !3)
+!1 = !DIFile(filename: "a.cc", directory: "/tmp")
+!2 = !{}
+!3 = !{!4}
+!4 = distinct !DISubprogram(name: "foo", linkageName: "_Z3fooi", scope: !1, file: !1, line: 5, type: !5, isLocal: false, isDefinition: true, scopeLine: 5, flags: DIFlagPrototyped, isOptimized: false, function: i32 (i32)* @_Z3fooi, variables: !2)
+!5 = !DISubroutineType(types: !6)
+!6 = !{!7, !7}
+!7 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
+!8 = !{i32 2, !"Dwarf Version", i32 4}
+!9 = !{i32 2, !"Debug Info Version", i32 3}
+!10 = !{!"clang version 3.8.0 (trunk 250750)"}
+!11 = !DILocalVariable(name: "a", arg: 1, scope: !4, file: !1, line: 5, type: !7)
+!12 = !DIExpression()
+!13 = !DILocation(line: 5, column: 13, scope: !4)
+!14 = !DILocation(line: 1, column: 5, scope: !15)
+!15 = distinct !DILexicalBlock(scope: !17, file: !16, line: 1, column: 5)
+!16 = !DIFile(filename: "./a.b", directory: "/tmp")
+!17 = !DILexicalBlockFile(scope: !4, file: !16, discriminator: 0)
+!18 = !DILocation(line: 1, column: 7, scope: !15)
+!19 = !DILocation(line: 1, column: 5, scope: !17)
+!20 = !DILocation(line: 2, column: 3, scope: !21)
+!21 = distinct !DILexicalBlock(scope: !15, file: !16, line: 1, column: 12)
+!22 = !DILocation(line: 4, column: 3, scope: !23)
+!23 = distinct !DILexicalBlock(scope: !15, file: !16, line: 3, column: 8)
+!24 = !DILocation(line: 7, column: 1, scope: !25)
+!25 = !DILexicalBlockFile(scope: !4, file: !1, discriminator: 0)