Index: llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp
+++ llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -1552,6 +1552,11 @@
     WideInc =
       cast<Instruction>(WidePhi->getIncomingValueForBlock(LatchBlock));
     WideIncExpr = SE->getSCEV(WideInc);
+    // Propagate the debug location associated with the original loop increment
+    // to the new (widened) increment.
+    auto *OrigInc =
+      cast<Instruction>(OrigPhi->getIncomingValueForBlock(LatchBlock));
+    WideInc->setDebugLoc(OrigInc->getDebugLoc());
   }
 
   DEBUG(dbgs() << "Wide IV: " << *WidePhi << "\n");
Index: llvm/trunk/test/DebugInfo/Generic/indvar-discriminator.ll
===================================================================
--- llvm/trunk/test/DebugInfo/Generic/indvar-discriminator.ll
+++ llvm/trunk/test/DebugInfo/Generic/indvar-discriminator.ll
@@ -0,0 +1,83 @@
+; RUN: opt -indvars -S < %s | FileCheck %s
+;
+; When the induction variable is widened by indvars, check that the debug loc
+; associated with the loop increment is correctly propagated.
+;
+; Test case obtained from the following source code:
+;
+; ////
+; extern int foo(int);  // line 1
+;
+; int bar(int X, int *A) {
+;   for (int i = 0; i < X; ++i)  // line 4
+;     A[i] = foo(i);
+;
+;   return A[0];
+; }
+; ///
+;
+; Check that the debug location for the loop increment still refers to
+; line 4, column 26, discriminator 2.
+;
+; CHECK-LABEL: for.body:
+; CHECK: [[PHI:%[0-9a-zA-Z.]+]] = phi i64 [
+; CHECK-LABEL: for.inc:
+; CHECK: add nuw nsw i64 [[PHI]], 1, !dbg ![[INDVARMD:[0-9]+]]
+; CHECK-DAG: ![[INDVARMD]] = !DILocation(line: 4, column: 26, scope: ![[INDVARSCOPEMD:[0-9]+]])
+; CHECK-DAG: ![[INDVARSCOPEMD]] = !DILexicalBlockFile(scope: !{{[0-9]+}}, file: !{{[0-9]+}}, discriminator: 2)
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+define i32 @bar(i32 %X, i32* %A) !dbg !5 {
+entry:
+  %cmp5 = icmp sgt i32 %X, 0, !dbg !7
+  br i1 %cmp5, label %for.body.lr.ph, label %for.end, !dbg !9
+
+for.body.lr.ph:
+  br label %for.body, !dbg !9
+
+for.body:
+  %i.06 = phi i32 [ 0, %for.body.lr.ph ], [ %inc, %for.inc ]
+  %call = call i32 @foo(i32 %i.06), !dbg !10
+  %idxprom = sext i32 %i.06 to i64, !dbg !11
+  %arrayidx = getelementptr inbounds i32, i32* %A, i64 %idxprom, !dbg !11
+  store i32 %call, i32* %arrayidx, align 4, !dbg !12
+  br label %for.inc, !dbg !11
+
+for.inc:
+  %inc = add nsw i32 %i.06, 1, !dbg !13
+  %cmp = icmp slt i32 %inc, %X, !dbg !7
+  br i1 %cmp, label %for.body, label %for.cond.for.end_crit_edge, !dbg !9, !llvm.loop !15
+
+for.cond.for.end_crit_edge:
+  br label %for.end, !dbg !9
+
+for.end:
+  %0 = load i32, i32* %A, align 4, !dbg !17
+  ret i32 %0, !dbg !18
+}
+
+declare i32 @foo(i32)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "", isOptimized: false, runtimeVersion: 0, emissionKind: LineTablesOnly, enums: !2)
+!1 = !DIFile(filename: "test.c", directory: "")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = distinct !DISubprogram(name: "bar", scope: !1, file: !1, line: 3, type: !6, isLocal: false, isDefinition: true, scopeLine: 3, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!6 = !DISubroutineType(types: !2)
+!7 = !DILocation(line: 4, column: 21, scope: !8)
+!8 = !DILexicalBlockFile(scope: !5, file: !1, discriminator: 1)
+!9 = !DILocation(line: 4, column: 3, scope: !8)
+!10 = !DILocation(line: 5, column: 12, scope: !5)
+!11 = !DILocation(line: 5, column: 5, scope: !5)
+!12 = !DILocation(line: 5, column: 10, scope: !5)
+!13 = !DILocation(line: 4, column: 26, scope: !14)
+!14 = !DILexicalBlockFile(scope: !5, file: !1, discriminator: 2)
+!15 = distinct !{!15, !16}
+!16 = !DILocation(line: 4, column: 3, scope: !5)
+!17 = !DILocation(line: 7, column: 10, scope: !5)
+!18 = !DILocation(line: 7, column: 3, scope: !5)