Index: include/llvm/IR/DebugInfoMetadata.h
===================================================================
--- include/llvm/IR/DebugInfoMetadata.h
+++ include/llvm/IR/DebugInfoMetadata.h
@@ -1369,14 +1369,30 @@
   /// represented in a single line entry.  In this case, no location
   /// should be set.
   ///
-  /// Currently the function does not create a new location. If the locations
-  /// are the same, or cannot be discriminated, the first location is returned.
-  /// Otherwise an empty location will be used.
+  /// Currently the function does not create a new 'valid' location. If the
+  /// locations are the same, or cannot be discriminated, the first location is
+  /// returned. Otherwise a dummy location of (line: 0, column: 0) is returned
+  /// with a scope of LocA, considering inlining context.
   static const DILocation *getMergedLocation(const DILocation *LocA,
                                              const DILocation *LocB) {
-    if (LocA && LocB && (LocA == LocB || !LocA->canDiscriminate(*LocB)))
+    if (!LocA || !LocB)
+      return nullptr;
+
+    if (LocA == LocB || !LocA->canDiscriminate(*LocB))
       return LocA;
-    return nullptr;
+
+    // If the locations can be discriminated, returns a dummy location.
+    while (auto *InlinedLoc = LocA->getInlinedAt())
+      LocA = InlinedLoc;
+    while (auto *InlinedLoc = LocB->getInlinedAt())
+      LocB = InlinedLoc;
+    assert(LocA->getScope()->getSubprogram() ==
+               LocB->getScope()->getSubprogram() &&
+           "Cannot merge debug locations in different subprograms.");
+    assert(&LocA->getContext() == &LocB->getContext() &&
+           "Cannot merge debug locations in different contexts.");
+
+    return DILocation::get(LocA->getContext(), 0, 0, LocA->getScope());
   }
 
   Metadata *getRawScope() const { return getOperand(0); }
Index: test/DebugInfo/Generic/instcombine-phi.ll
===================================================================
--- test/DebugInfo/Generic/instcombine-phi.ll
+++ test/DebugInfo/Generic/instcombine-phi.ll
@@ -25,7 +25,7 @@
 ; CHECK-LABEL: if.end:
 ; CHECK: %[[PHI:.*]] = phi i32 [ %call, %if.then ], [ %call1, %if.else ]
 ; CHECK: sub nsw i32 %b, %[[PHI]]
-; CHECK-NOT: !dbg
+; CHECK: !dbg [[DBG1:![0-9]+]]
 ; CHECK: ret i32
 
 define i32 @binop(i32 %a, i32 %b) !dbg !6 {
@@ -67,7 +67,7 @@
 ; CHECK-LABEL: if.end:
 ; CHECK: %[[PHI:.*]] = phi i32 [ %call, %if.then ], [ %call1, %if.else ]
 ; CHECK: icmp slt i32 %[[PHI]], %b
-; CHECK-NOT: !dbg
+; CHECK: !dbg [[DBG2:![0-9]+]]
 ; CHECK: ret i32
 
 define i32 @cmp(i32 %a, i32 %b) !dbg !15 {
@@ -109,7 +109,7 @@
 ; CHECK-LABEL: if.end:
 ; CHECK: %[[PHI:.*]] = phi i64 [ %call, %if.then ], [ %call1, %if.else ]
 ; CHECK: getelementptr inbounds i32, i32* %b, i64 %[[PHI]]
-; CHECK-NOT: !dbg
+; CHECK: !dbg [[DBG3:![0-9]+]]
 ; CHECK: ret i32*
 
 define i32* @gep(i32 %a, i32* %b) !dbg !23 {
@@ -150,7 +150,7 @@
 ; CHECK-LABEL: if.end:
 ; CHECK: %[[PHI:.*]] = phi i32* [ %call, %if.then ], [ %call1, %if.else ]
 ; CHECK: load i32, i32* %[[PHI]]
-; CHECK-NOT: !dbg
+; CHECK: !dbg [[DBG4:![0-9]+]]
 ; CHECK: ret i32
 
 define i32 @load(i32 %a) !dbg !31 {
@@ -191,7 +191,7 @@
 ; CHECK-LABEL: if.end:
 ; CHECK: %[[PHI:.*]] = phi i32 [ %call, %if.then ], [ %call1, %if.else ]
 ; CHECK: sext i32 %[[PHI]] to i64
-; CHECK-NOT: !dbg
+; CHECK: !dbg [[DBG5:![0-9]+]]
 ; CHECK: ret i64
 
 define i64 @cast(i32 %a) !dbg !39 {
@@ -232,7 +232,7 @@
 ; CHECK-LABEL: if.end:
 ; CHECK: %[[PHI:.*]] = phi i32 [ %call, %if.then ], [ %call1, %if.else ]
 ; CHECK: add nsw i32 %[[PHI]], -5
-; CHECK-NOT: !dbg
+; CHECK: !dbg [[DBG6:![0-9]+]]
 ; CHECK: ret i32
 
 define i32 @binop_const(i32 %a) !dbg !45 {
@@ -274,7 +274,7 @@
 ; CHECK-LABEL: if.end:
 ; CHECK: %[[PHI:.*]] = phi i32 [ %call, %if.then ], [ %call1, %if.else ]
 ; CHECK: icmp slt i32 %[[PHI]], 10
-; CHECK-NOT: !dbg
+; CHECK: !dbg [[DBG7:![0-9]+]]
 ; CHECK: ret i32
 
 define i32 @cmp_const(i32 %a) !dbg !53 {
@@ -308,6 +308,21 @@
 !llvm.dbg.cu = !{!0}
 !llvm.module.flags = !{!3, !4}
 
+; CHECK: [[BINOP:![0-9]+]] = distinct !DISubprogram(name: "binop"{{.+}})
+; CHECK: [[DBG1]] = !DILocation(line: 0, scope: [[BINOP]])
+; CHECK: [[CMP:![0-9]+]] = distinct !DISubprogram(name: "cmp"{{.+}})
+; CHECK: [[DBG2]] = !DILocation(line: 0, scope: [[CMP]])
+; CHECK: [[GEP:![0-9]+]] = distinct !DISubprogram(name: "gep"{{.+}})
+; CHECK: [[DBG3]] = !DILocation(line: 0, scope: [[GEP]])
+; CHECK: [[LOAD:![0-9]+]] = distinct !DISubprogram(name: "load"{{.+}})
+; CHECK: [[DBG4]] = !DILocation(line: 0, scope: [[LOAD]])
+; CHECK: [[CAST:![0-9]+]] = distinct !DISubprogram(name: "cast"{{.+}})
+; CHECK: [[DBG5]] = !DILocation(line: 0, scope: [[CAST]])
+; CHECK: [[BINOP_CONST:![0-9]+]] = distinct !DISubprogram(name: "binop_const"{{.+}})
+; CHECK: [[DBG6]] = !DILocation(line: 0, scope: [[BINOP_CONST]])
+; CHECK: [[CMP_CONST:![0-9]+]] = distinct !DISubprogram(name: "cmp_const"{{.+}})
+; CHECK: [[DBG7]] = !DILocation(line: 0, scope: [[CMP_CONST]])
+
 !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 = !{}
Index: test/DebugInfo/Generic/simplifycfg_sink_last_inst.ll
===================================================================
--- test/DebugInfo/Generic/simplifycfg_sink_last_inst.ll
+++ test/DebugInfo/Generic/simplifycfg_sink_last_inst.ll
@@ -25,7 +25,7 @@
 ; CHECK-LABEL: if.end:
 ; CHECK: %[[PHI:.*]] = phi i32 [ %call1, %if.else ], [ %call, %if.then ]
 ; CHECK: sub nsw i32 %b, %[[PHI]]
-; CHECK-NOT: !dbg
+; CHECK: !dbg [[DBG1:![0-9]+]]
 ; CHECK: ret i32
 
 define i32 @test(i32 %a, i32 %b) !dbg !6 {
@@ -61,9 +61,8 @@
 ; CHECK: define i32 @test2
 ; CHECK-LABEL: if.end:
 ; CHECK: %[[PHI:.*]] = phi i32 [ %call1, %if.else ], [ %call, %if.then ]
-; CHECK: sub nsw i32 %b, %[[PHI]], !dbg ![[DBG:.*]]
+; CHECK: sub nsw i32 %b, %[[PHI]], !dbg ![[DBG2:.*]]
 ; CHECK: ret i32
-; CHECK: ![[DBG]] = !DILocation(line: 17, scope: !{{.*}})
 
 define i32 @test2(i32 %a, i32 %b) !dbg !15 {
 entry:
@@ -91,6 +90,10 @@
 !llvm.dbg.cu = !{!0}
 !llvm.module.flags = !{!3, !4}
 
+; CHECK: [[TEST:![0-9]+]] = distinct !DISubprogram(name: "test"{{.+}})
+; CHECK: [[DBG1]] = !DILocation(line: 0, scope: [[TEST]])
+; CHECK: ![[DBG2]] = !DILocation(line: 17, scope: !{{.*}})
+
 !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 = !{}
Index: test/DebugInfo/Generic/store-tail-merge.ll
===================================================================
--- test/DebugInfo/Generic/store-tail-merge.ll
+++ test/DebugInfo/Generic/store-tail-merge.ll
@@ -22,7 +22,8 @@
 ; CHECK:       if.end:
 ; CHECK-NEXT:  %storemerge = phi
 ; This final check is the "real" test, verify no !dbg on the store.
-; CHECK-NEXT:  store i32 %storemerge{{.*}}, align 4{{$}}
+; CHECK-NEXT:  store i32 %storemerge{{.*}}, align 4
+; CHECK: !dbg [[DBG:![0-9]+]]
 ;
 ; ModuleID = 'test1.ll'
 source_filename = "test.c"
@@ -56,6 +57,9 @@
 !llvm.dbg.cu = !{!0}
 !llvm.module.flags = !{!3, !4}
 
+; CHECK: [[FOO:![0-9]+]] = distinct !DISubprogram(name: "foo"{{.+}})
+; CHECK: [[DBG]] = !DILocation(line: 0, scope: [[FOO]])
+
 !0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "", isOptimized: false, runtimeVersion: 0, emissionKind: LineTablesOnly, enums: !2)
 !1 = !DIFile(filename: "test.c", directory: "/home/probinson/projects/scratch")
 !2 = !{}
Index: test/Transforms/SimplifyCFG/remove-debug-2.ll
===================================================================
--- test/Transforms/SimplifyCFG/remove-debug-2.ll
+++ test/Transforms/SimplifyCFG/remove-debug-2.ll
@@ -13,12 +13,13 @@
 ; CHECK: icmp ne {{.+}}!dbg ![[DLOC2:[0-9]+]]
 ; CHECK: [[VREG:%[^ ]+]] = select
 ; CHECK: store i32 [[VREG]]
-; CHECK-NOT: !dbg
-; CHECK-SAME: {{$}}
-; CHECK: ret {{.+}}!dbg ![[DLOC3:[0-9]+]]
-; CHECK: ![[DLOC1]] = !DILocation(line: 2
-; CHECK: ![[DLOC2]] = !DILocation(line: 3
-; CHECK: ![[DLOC3]] = !DILocation(line: 5
+; CHECK-SAME: !dbg ![[DLOC3:[0-9]+]]
+; CHECK: ret {{.+}}!dbg ![[DLOC4:[0-9]+]]
+; CHECK-DAG: [[FOO:![0-9]+]] = distinct !DISubprogram(name: "foo"{{.+}})
+; CHECK-DAG: ![[DLOC1]] = !DILocation(line: 2
+; CHECK-DAG: ![[DLOC2]] = !DILocation(line: 3
+; CHECK-DAG: ![[DLOC3]] = !DILocation(line: 0, scope: [[FOO]])
+; CHECK-DAG: ![[DLOC4]] = !DILocation(line: 5
 
 target triple = "x86_64-unknown-linux-gnu"