diff --git a/clang/lib/CodeGen/CoverageMappingGen.cpp b/clang/lib/CodeGen/CoverageMappingGen.cpp
index ae4e6d4c88c02..3b912e0f83208 100644
--- a/clang/lib/CodeGen/CoverageMappingGen.cpp
+++ b/clang/lib/CodeGen/CoverageMappingGen.cpp
@@ -17,6 +17,7 @@
 #include "clang/Basic/FileManager.h"
 #include "clang/Frontend/FrontendDiagnostic.h"
 #include "clang/Lex/Lexer.h"
+#include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ProfileData/Coverage/CoverageMapping.h"
@@ -278,10 +279,36 @@ class CoverageMappingBuilder {
     return SM.getLocForEndOfFile(SM.getFileID(Loc));
   }
 
-  /// Find out where the current file is included or macro is expanded.
-  SourceLocation getIncludeOrExpansionLoc(SourceLocation Loc) {
-    return Loc.isMacroID() ? SM.getImmediateExpansionRange(Loc).getBegin()
-                           : SM.getIncludeLoc(SM.getFileID(Loc));
+  /// Find out where a macro is expanded. If the immediate result is a
+  /// <scratch space>, keep looking until the result isn't. Return a pair of
+  /// \c SourceLocation. The first object is always the begin sloc of found
+  /// result. The second should be checked by the caller: if it has value, it's
+  /// the end sloc of the found result. Otherwise the while loop didn't get
+  /// executed, which means the location wasn't changed and the caller has to
+  /// learn the end sloc from somewhere else.
+  std::pair<SourceLocation, std::optional<SourceLocation>>
+  getNonScratchExpansionLoc(SourceLocation Loc) {
+    std::optional<SourceLocation> EndLoc = std::nullopt;
+    while (Loc.isMacroID() &&
+           SM.isWrittenInScratchSpace(SM.getSpellingLoc(Loc))) {
+      auto ExpansionRange = SM.getImmediateExpansionRange(Loc);
+      Loc = ExpansionRange.getBegin();
+      EndLoc = ExpansionRange.getEnd();
+    }
+    return std::make_pair(Loc, EndLoc);
+  }
+
+  /// Find out where the current file is included or macro is expanded. If
+  /// \c AcceptScratch is set to false, keep looking for expansions until the
+  /// found sloc is not a <scratch space>.
+  SourceLocation getIncludeOrExpansionLoc(SourceLocation Loc,
+                                          bool AcceptScratch = true) {
+    if (!Loc.isMacroID())
+      return SM.getIncludeLoc(SM.getFileID(Loc));
+    Loc = SM.getImmediateExpansionRange(Loc).getBegin();
+    if (AcceptScratch)
+      return Loc;
+    return getNonScratchExpansionLoc(Loc).first;
   }
 
   /// Return true if \c Loc is a location in a built-in macro.
@@ -325,16 +352,35 @@ class CoverageMappingBuilder {
 
     llvm::SmallSet<FileID, 8> Visited;
     SmallVector<std::pair<SourceLocation, unsigned>, 8> FileLocs;
-    for (const auto &Region : SourceRegions) {
+    for (auto &Region : SourceRegions) {
       SourceLocation Loc = Region.getBeginLoc();
+
+      // Replace Region with its definition if it is in <scratch space>.
+      auto NonScratchExpansionLoc = getNonScratchExpansionLoc(Loc);
+      auto EndLoc = NonScratchExpansionLoc.second;
+      if (EndLoc.has_value()) {
+        Loc = NonScratchExpansionLoc.first;
+        Region.setStartLoc(Loc);
+        Region.setEndLoc(EndLoc.value());
+      }
+
+      // Replace Loc with FileLoc if it is expanded with system headers.
+      if (!SystemHeadersCoverage && SM.isInSystemMacro(Loc)) {
+        auto BeginLoc = SM.getSpellingLoc(Loc);
+        auto EndLoc = SM.getSpellingLoc(Region.getEndLoc());
+        if (SM.isWrittenInSameFile(BeginLoc, EndLoc)) {
+          Loc = SM.getFileLoc(Loc);
+          Region.setStartLoc(Loc);
+          Region.setEndLoc(SM.getFileLoc(Region.getEndLoc()));
+        }
+      }
+
       FileID File = SM.getFileID(Loc);
       if (!Visited.insert(File).second)
         continue;
 
-      // Do not map FileID's associated with system headers unless collecting
-      // coverage from system headers is explicitly enabled.
-      if (!SystemHeadersCoverage && SM.isInSystemHeader(SM.getSpellingLoc(Loc)))
-        continue;
+      assert(SystemHeadersCoverage ||
+             !SM.isInSystemHeader(SM.getSpellingLoc(Loc)));
 
       unsigned Depth = 0;
       for (SourceLocation Parent = getIncludeOrExpansionLoc(Loc);
@@ -503,7 +549,7 @@ class CoverageMappingBuilder {
     SourceRegionFilter Filter;
     for (const auto &FM : FileIDMapping) {
       SourceLocation ExpandedLoc = FM.second.second;
-      SourceLocation ParentLoc = getIncludeOrExpansionLoc(ExpandedLoc);
+      SourceLocation ParentLoc = getIncludeOrExpansionLoc(ExpandedLoc, false);
       if (ParentLoc.isInvalid())
         continue;
 
@@ -816,6 +862,10 @@ struct CounterCoverageMappingBuilder
   /// A stack of currently live regions.
   llvm::SmallVector<SourceMappingRegion> RegionStack;
 
+  /// Set if the Expr should be handled as a leaf even if it is kind of binary
+  /// logical ops (&&, ||).
+  llvm::DenseSet<const Stmt *> LeafExprSet;
+
   /// An object to manage MCDC regions.
   MCDCCoverageBuilder MCDCBuilder;
 
@@ -1041,7 +1091,10 @@ struct CounterCoverageMappingBuilder
     // region onto RegionStack but immediately pop it (which adds it to the
     // function's SourceRegions) because it doesn't apply to any other source
     // code other than the Condition.
-    if (CodeGenFunction::isInstrumentedCondition(C)) {
+    // With !SystemHeadersCoverage, binary logical ops in system headers may be
+    // treated as instrumentable conditions.
+    if (CodeGenFunction::isInstrumentedCondition(C) ||
+        LeafExprSet.count(CodeGenFunction::stripCond(C))) {
       MCDCConditionID ID = MCDCBuilder.getCondID(C);
       MCDCConditionID TrueID = IDPair.TrueID;
       MCDCConditionID FalseID = IDPair.FalseID;
@@ -1977,7 +2030,20 @@ struct CounterCoverageMappingBuilder
                        subtractCounters(ParentCount, TrueCount));
   }
 
+  /// Check if E belongs to system headers.
+  bool isExprInSystemHeader(const BinaryOperator *E) const {
+    return (!SystemHeadersCoverage &&
+            SM.isInSystemHeader(SM.getSpellingLoc(E->getOperatorLoc())) &&
+            SM.isInSystemHeader(SM.getSpellingLoc(E->getBeginLoc())) &&
+            SM.isInSystemHeader(SM.getSpellingLoc(E->getEndLoc())));
+  }
+
   void VisitBinLAnd(const BinaryOperator *E) {
+    if (isExprInSystemHeader(E)) {
+      LeafExprSet.insert(E);
+      return;
+    }
+
     bool IsRootNode = MCDCBuilder.isIdle();
 
     // Keep track of Binary Operator and assign MCDC condition IDs.
@@ -2031,6 +2097,11 @@ struct CounterCoverageMappingBuilder
   }
 
   void VisitBinLOr(const BinaryOperator *E) {
+    if (isExprInSystemHeader(E)) {
+      LeafExprSet.insert(E);
+      return;
+    }
+
     bool IsRootNode = MCDCBuilder.isIdle();
 
     // Keep track of Binary Operator and assign MCDC condition IDs.
diff --git a/clang/test/CoverageMapping/builtinmacro.c b/clang/test/CoverageMapping/builtinmacro.c
index abcdc191523a5..5d5a176aa7d87 100644
--- a/clang/test/CoverageMapping/builtinmacro.c
+++ b/clang/test/CoverageMapping/builtinmacro.c
@@ -4,7 +4,7 @@
 
 // CHECK: filename
 const char *filename (const char *name) { // CHECK-NEXT: File 0, [[@LINE]]:41 -> [[@LINE+3]]:2 = #0
-  static const char this_file[] = __FILE__;
+  static const char this_file[] = __FILE__; // CHECK-NEXT: File 0, [[@LINE]]:35 -> [[@LINE]]:35 = #0
   return this_file;
 }
 
diff --git a/clang/test/CoverageMapping/macros.c b/clang/test/CoverageMapping/macros.c
index 6bd3be434139a..fcf21170ef135 100644
--- a/clang/test/CoverageMapping/macros.c
+++ b/clang/test/CoverageMapping/macros.c
@@ -80,12 +80,14 @@ void func7(void) { // CHECK-NEXT: File 0, [[@LINE]]:18 -> [[@LINE+6]]:2 = #0
   int kk,ll;       // CHECK-NEXT: File 0, [[@LINE+1]]:7 -> [[@LINE+1]]:8 = #0
   if (k)           // CHECK-NEXT: Branch,File 0, [[@LINE]]:7 -> [[@LINE]]:8 = #1
     m(k);          // CHECK-NEXT: Gap,File 0, [[@LINE-1]]:9 -> [[@LINE]]:5 = #1
-  else             // CHECK-NEXT: Expansion,File 0, [[@LINE-1]]:5 -> [[@LINE-1]]:6 = #0
+  else             // CHECK-NEXT: Expansion,File 0, [[@LINE-1]]:5 -> [[@LINE-1]]:6 = #1
     l = m(l);      // CHECK-NEXT: Gap,File 0, [[@LINE-2]]:7 -> [[@LINE]]:5 = (#0 - #1)
 }                  // CHECK-NEXT: File 0, [[@LINE-1]]:5 -> [[@LINE-1]]:10 = (#0 - #1)
                    // CHECK-NEXT: Expansion,File 0, [[@LINE-2]]:9 -> [[@LINE-2]]:10 = (#0 - #1)
-                   // CHECK-NEXT: File 1, [[@LINE-9]]:14 -> [[@LINE-9]]:18 = #0
-                   // CHECK-NEXT: File 2, [[@LINE-10]]:14 -> [[@LINE-10]]:15 = (#0 - #1)
+                   // CHECK-NEXT: File 1, [[@LINE-9]]:14 -> [[@LINE-9]]:17 = #1
+                   // CHECK-NEXT: File 1, [[@LINE-10]]:14 -> [[@LINE-10]]:18 = #0
+                   // CHECK-NEXT: File 2, [[@LINE-11]]:14 -> [[@LINE-11]]:17 = (#0 - #1)
+                   // CHECK-NEXT: File 2, [[@LINE-12]]:14 -> [[@LINE-12]]:15 = (#0 - #1)
 
 int main(int argc, const char *argv[]) {
   func();
diff --git a/clang/test/CoverageMapping/mcdc-scratch-space.c b/clang/test/CoverageMapping/mcdc-scratch-space.c
new file mode 100644
index 0000000000000..2b5b12d9dcad6
--- /dev/null
+++ b/clang/test/CoverageMapping/mcdc-scratch-space.c
@@ -0,0 +1,65 @@
+// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c99 -fcoverage-mcdc -fprofile-instrument=clang -fcoverage-mapping -dump-coverage-mapping -emit-llvm-only %s | FileCheck %s
+
+// CHECK: builtin_macro0:
+int builtin_macro0(int a) {
+  // CHECK: Decision,File 0, [[@LINE+1]]:11 -> [[@LINE+2]]:15 = M:0, C:2
+  return (__LINE__ // CHECK: Branch,File 0, [[@LINE]]:11 -> [[@LINE]]:11 = 0, 0 [1,2,0]
+          && a); //   CHECK: Branch,File 0, [[@LINE]]:14 -> [[@LINE]]:15 = #2, (#1 - #2) [2,0,0]
+}
+
+// CHECK: builtin_macro1:
+int builtin_macro1(int a) {
+  // CHECK: Decision,File 0, [[@LINE+1]]:11 -> [[@LINE+2]]:22 = M:0, C:2
+  return (a // CHECK: Branch,File 0, [[@LINE]]:11 -> [[@LINE]]:12 = (#0 - #1), #1 [1,0,2]
+          || __LINE__); // CHECK: Branch,File 0, [[@LINE]]:14 -> [[@LINE]]:14 = 0, 0 [2,0,0]
+}
+
+#define PRE(x) pre_##x
+
+// CHECK: pre0:
+int pre0(int pre_a, int b_post) {
+  // CHECK: Decision,File 0, [[@LINE+2]]:11 -> [[@LINE+3]]:20 = M:0, C:2
+  // CHECK: Expansion,File 0, [[@LINE+1]]:11 -> [[@LINE+1]]:14 = #0 (Expanded file = 1)
+  return (PRE(a)
+          && b_post);
+  // CHECK: Branch,File 0, [[@LINE-1]]:14 -> [[@LINE-1]]:20 = #2, (#1 - #2) [2,0,0]
+  // CHECK: Branch,File 1, [[@LINE-9]]:16 -> [[@LINE-9]]:22 = #1, (#0 - #1) [1,2,0]
+}
+
+#define pre_foo pre_a
+
+// CHECK: pre1:
+int pre1(int pre_a, int b_post) {
+  // CHECK: Decision,File 0, [[@LINE+3]]:11 -> [[@LINE+4]]:20 = M:0, C:2
+  // CHECK: Expansion,File 0, [[@LINE+2]]:11 -> [[@LINE+2]]:14 = #0 (Expanded file = 1)
+  // CHECK: Branch,File 0, [[@LINE+2]]:14 -> [[@LINE+2]]:20 = #2, (#1 - #2) [2,0,0]
+  return (PRE(foo)
+          && b_post);
+  // CHECK: Expansion,File 1, 17:16 -> 17:20 = #0 (Expanded file = 2)
+  // CHECK: Branch,File 2, 29:17 -> 29:22 = #1, (#0 - #1) [1,2,0]
+}
+
+#define POST(x) x##_post
+
+// CHECK: post0:
+int post0(int pre_a, int b_post) {
+  // CHECK: Decision,File 0, [[@LINE+2]]:11 -> [[@LINE+3]]:18 = M:0, C:2
+  // CHECK: Branch,File 0, [[@LINE+1]]:11 -> [[@LINE+1]]:16 = (#0 - #1), #1 [1,0,2]
+  return (pre_a
+          || POST(b));
+  // CHECK: Expansion,File 0, [[@LINE-1]]:14 -> [[@LINE-1]]:18 = #1 (Expanded file = 1)
+  // CHECK: Branch,File 1, [[@LINE-9]]:17 -> [[@LINE-9]]:20 = (#1 - #2), #2 [2,0,0]
+}
+
+#define bar_post b_post
+
+// CHECK: post1:
+int post1(int pre_a, int b_post) {
+  // CHECK: Decision,File 0, [[@LINE+3]]:11 -> [[@LINE+4]]:18 = M:0, C:2
+  // CHECK: Branch,File 0, [[@LINE+2]]:11 -> [[@LINE+2]]:16 = (#0 - #1), #1 [1,0,2]
+  // CHECK: Expansion,File 0, [[@LINE+2]]:14 -> [[@LINE+2]]:18 = 0 (Expanded file = 1)
+  return (pre_a
+          || POST(bar));
+  // CHECK: Expansion,File 1, 42:17 -> 42:18 = #1 (Expanded file = 2)
+  // CHECK: Branch,File 2, 54:18 -> 54:24 = (#1 - #2), #2 [2,0,0]
+}
diff --git a/clang/test/CoverageMapping/mcdc-system-headers.cpp b/clang/test/CoverageMapping/mcdc-system-headers.cpp
new file mode 100644
index 0000000000000..4dfbb17c2bba8
--- /dev/null
+++ b/clang/test/CoverageMapping/mcdc-system-headers.cpp
@@ -0,0 +1,50 @@
+// RUN: %clang_cc1 -std=c++11 -triple %itanium_abi_triple -fprofile-instrument=clang -fcoverage-mapping -dump-coverage-mapping -fcoverage-mcdc -mllvm -system-headers-coverage -emit-llvm-only -o - %s | FileCheck %s --check-prefixes=CHECK,W_SYS
+// RUN: %clang_cc1 -std=c++11 -triple %itanium_abi_triple -fprofile-instrument=clang -fcoverage-mapping -dump-coverage-mapping -fcoverage-mcdc -emit-llvm-only -o - %s | FileCheck %s --check-prefixes=CHECK,X_SYS
+
+#ifdef IS_SYSHEADER
+
+#pragma clang system_header
+#define CONST 42
+#define EXPR1(x) (x)
+#define EXPR2(x) ((x) && (x))
+
+#else
+
+#define IS_SYSHEADER
+#include __FILE__
+
+// CHECK: _Z5func0i:
+int func0(int a) {
+  // CHECK: Decision,File 0, [[@LINE+3]]:11 -> [[@LINE+3]]:21 = M:0, C:2
+  // W_SYS: Expansion,File 0, [[@LINE+2]]:11 -> [[@LINE+2]]:16 = #0 (Expanded file = 1)
+  // X_SYS: Branch,File 0, [[@LINE+1]]:11 -> [[@LINE+1]]:11 = 0, 0 [1,2,0]
+  return (CONST && a);
+  // CHECK: Branch,File 0, [[@LINE-1]]:20 -> [[@LINE-1]]:21 = #2, (#1 - #2) [2,0,0]
+  // W_SYS: Branch,File 1, [[@LINE-16]]:15 -> [[@LINE-16]]:17 = 0, 0 [1,2,0]
+}
+
+// CHECK: _Z5func1ii:
+int func1(int a, int b) {
+  // CHECK: Decision,File 0, [[@LINE+2]]:11 -> [[@LINE+2]]:21 = M:0, C:2
+  // CHECK: Branch,File 0, [[@LINE+1]]:11 -> [[@LINE+1]]:12 = (#0 - #1), #1 [1,0,2]
+  return (a || EXPR1(b));
+  // W_SYS: Expansion,File 0, [[@LINE-1]]:16 -> [[@LINE-1]]:21 = #1 (Expanded file = 1)
+  // W_SYS: Branch,File 1, [[@LINE-24]]:18 -> [[@LINE-24]]:21 = (#1 - #2), #2 [2,0,0]
+  // X_SYS: Branch,File 0, [[@LINE-3]]:16 -> [[@LINE-3]]:16 = (#1 - #2), #2 [2,0,0]
+}
+
+// CHECK: _Z5func2ii:
+int func2(int a, int b) {
+  // W_SYS: Decision,File 0, [[@LINE+5]]:11 -> [[@LINE+5]]:28 = M:0, C:3
+  // X_SYS: Decision,File 0, [[@LINE+4]]:11 -> [[@LINE+4]]:28 = M:0, C:2
+  // W_SYS: Expansion,File 0, [[@LINE+3]]:11 -> [[@LINE+3]]:16 = #0 (Expanded file = 1)
+  // W_SYS: Expansion,File 0, [[@LINE+2]]:23 -> [[@LINE+2]]:28 = #1 (Expanded file = 2)
+  // X_SYS: Branch,File 0, [[@LINE+1]]:11 -> [[@LINE+1]]:11 = #1, (#0 - #1) [1,2,0]
+  return (EXPR2(a) && EXPR1(a));
+  // W_SYS: Branch,File 1, [[@LINE-35]]:19 -> [[@LINE-35]]:22 = #3, (#0 - #3) [1,3,0]
+  // W_SYS: Branch,File 1, [[@LINE-36]]:26 -> [[@LINE-36]]:29 = #4, (#3 - #4) [3,2,0]
+  // W_SYS: Branch,File 2, [[@LINE-38]]:18 -> [[@LINE-38]]:21 = #2, (#1 - #2) [2,0,0]
+  // X_SYS: Branch,File 0, [[@LINE-4]]:23 -> [[@LINE-4]]:23 = #2, (#1 - #2) [2,0,0]
+}
+
+#endif