Index: clang/include/clang/Basic/DiagnosticGroups.td
===================================================================
--- clang/include/clang/Basic/DiagnosticGroups.td
+++ clang/include/clang/Basic/DiagnosticGroups.td
@@ -693,6 +693,7 @@
 def GNUZeroLineDirective : DiagGroup<"gnu-zero-line-directive">;
 def GNUZeroVariadicMacroArguments : DiagGroup<"gnu-zero-variadic-macro-arguments">;
 def Fallback : DiagGroup<"fallback">;
+def MisleadingIndentation : DiagGroup<"misleading-indentation">;
 
 // This covers both the deprecated case (in C++98)
 // and the extension case (in C++11 onwards).
@@ -884,7 +885,7 @@
 // Note that putting warnings in -Wall will not disable them by default. If a
 // warning should be active _only_ when -Wall is passed in, mark it as
 // DefaultIgnore in addition to putting it here.
-def All : DiagGroup<"all", [Most, Parentheses, Switch, SwitchBool]>;
+def All : DiagGroup<"all", [Most, Parentheses, Switch, SwitchBool, MisleadingIndentation]>;
 
 // Warnings that should be in clang-cl /w4.
 def : DiagGroup<"CL4", [All, Extra]>;
Index: clang/include/clang/Basic/DiagnosticParseKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticParseKinds.td
+++ clang/include/clang/Basic/DiagnosticParseKinds.td
@@ -61,6 +61,13 @@
   "remove unnecessary ';' to silence this warning">,
   InGroup<ExtraSemiStmt>, DefaultIgnore;
 
+def warn_misleading_indentation : Warning<
+  "misleading indentation; this is not part of "
+  "the previous '%select{if|else|for|while}0'">,
+  InGroup<MisleadingIndentation>, DefaultIgnore;
+def note_previous_statement : Note<
+  "previous statement is here">;
+
 def ext_thread_before : Extension<"'__thread' before '%0'">;
 def ext_keyword_as_ident : ExtWarn<
   "keyword '%0' will be made available as an identifier "
Index: clang/include/clang/Lex/Preprocessor.h
===================================================================
--- clang/include/clang/Lex/Preprocessor.h
+++ clang/include/clang/Lex/Preprocessor.h
@@ -932,6 +932,12 @@
     return TheModuleLoader.HadFatalFailure;
   }
 
+  /// Retrieve the number of Directives that have been processed by the
+  /// Preprocessor.
+  unsigned getNumDirectives() const {
+    return NumDirectives;
+  }
+
   /// True if we are currently preprocessing a #if or #elif directive
   bool isParsingIfOrElifDirective() const {
     return ParsingIfOrElifDirective;
Index: clang/include/clang/Parse/Parser.h
===================================================================
--- clang/include/clang/Parse/Parser.h
+++ clang/include/clang/Parse/Parser.h
@@ -2266,11 +2266,13 @@
     return isTypeSpecifierQualifier();
   }
 
+public:
   /// isCXXDeclarationStatement - C++-specialized function that disambiguates
   /// between a declaration or an expression statement, when parsing function
   /// bodies. Returns true for declaration, false for expression.
   bool isCXXDeclarationStatement();
 
+private:
   /// isCXXSimpleDeclaration - C++-specialized function that disambiguates
   /// between a simple-declaration or an expression-statement.
   /// If during the disambiguation process a parsing error is encountered,
Index: clang/lib/Parse/ParseStmt.cpp
===================================================================
--- clang/lib/Parse/ParseStmt.cpp
+++ clang/lib/Parse/ParseStmt.cpp
@@ -1191,6 +1191,55 @@
   return false;
 }
 
+namespace {
+
+enum MisleadingStatementKind { MSK_if, MSK_else, MSK_for, MSK_while };
+
+struct MisleadingIndentationChecker {
+  Parser &P;
+  SourceLocation StmtLoc;
+  SourceLocation PrevLoc;
+  unsigned NumDirectives;
+  MisleadingStatementKind Kind;
+  bool NeedsChecking;
+  bool HasBraces;
+  MisleadingIndentationChecker(Parser &P, MisleadingStatementKind K,
+                               SourceLocation SL)
+      : P(P), StmtLoc(SL), PrevLoc(P.getCurToken().getLocation()),
+        NumDirectives(P.getPreprocessor().getNumDirectives()), Kind(K),
+        NeedsChecking(true), HasBraces(P.getCurToken().is(tok::l_brace)) {
+        }
+  void Check(bool ShouldCheck) {
+    NeedsChecking = false;
+    Token Tok = P.getCurToken();
+    if (!ShouldCheck || HasBraces ||
+        NumDirectives != P.getPreprocessor().getNumDirectives() ||
+        Tok.isOneOf(tok::semi, tok::r_brace) || Tok.isAnnotation() ||
+        Tok.getLocation().isMacroID() || PrevLoc.isMacroID() ||
+        StmtLoc.isMacroID())
+      return;
+    SourceManager &SM = P.getPreprocessor().getSourceManager();
+    unsigned PrevColNum = SM.getSpellingColumnNumber(PrevLoc);
+    unsigned CurColNum = SM.getSpellingColumnNumber(Tok.getLocation());
+    unsigned StmtColNum = SM.getSpellingColumnNumber(StmtLoc);
+
+    if (PrevColNum != 0 && CurColNum != 0 && StmtColNum != 0 &&
+        ((PrevColNum > StmtColNum && PrevColNum == CurColNum) ||
+         !Tok.isAtStartOfLine())) {
+      if (SM.getPresumedLineNumber(StmtLoc) ==
+          SM.getPresumedLineNumber(Tok.getLocation()))
+        return;
+      P.Diag(Tok.getLocation(), diag::warn_misleading_indentation)
+          << Kind;
+      P.Diag(StmtLoc, diag::note_previous_statement);
+    }
+  }
+  ~MisleadingIndentationChecker() {
+    assert(!NeedsChecking && "Check Has not been called");
+  }
+};
+
+}
 
 /// ParseIfStatement
 ///       if-statement: [C99 6.8.4.1]
@@ -1265,6 +1314,8 @@
   //
   ParseScope InnerScope(this, Scope::DeclScope, C99orCXX, Tok.is(tok::l_brace));
 
+  MisleadingIndentationChecker MIChecker(*this, MSK_if, IfLoc);
+
   // Read the 'then' stmt.
   SourceLocation ThenStmtLoc = Tok.getLocation();
 
@@ -1278,6 +1329,8 @@
     ThenStmt = ParseStatement(&InnerStatementTrailingElseLoc);
   }
 
+  MIChecker.Check(Tok.isNot(tok::kw_else));
+
   // Pop the 'if' scope if needed.
   InnerScope.Exit();
 
@@ -1305,12 +1358,16 @@
     ParseScope InnerScope(this, Scope::DeclScope, C99orCXX,
                           Tok.is(tok::l_brace));
 
+    MisleadingIndentationChecker MIChecker(*this, MSK_else, ElseLoc);
+
     EnterExpressionEvaluationContext PotentiallyDiscarded(
         Actions, Sema::ExpressionEvaluationContext::DiscardedStatement, nullptr,
         Sema::ExpressionEvaluationContextRecord::EK_Other,
         /*ShouldEnter=*/ConstexprCondition && *ConstexprCondition);
     ElseStmt = ParseStatement();
 
+    MIChecker.Check(ElseStmt.isUsable());
+
     // Pop the 'else' scope if needed.
     InnerScope.Exit();
   } else if (Tok.is(tok::code_completion)) {
@@ -1484,9 +1541,12 @@
   //
   ParseScope InnerScope(this, Scope::DeclScope, C99orCXX, Tok.is(tok::l_brace));
 
+  MisleadingIndentationChecker MIChecker(*this, MSK_while, WhileLoc);
+
   // Read the body statement.
   StmtResult Body(ParseStatement(TrailingElseLoc));
 
+  MIChecker.Check(Body.isUsable());
   // Pop the body scope if needed.
   InnerScope.Exit();
   WhileScope.Exit();
@@ -1918,9 +1978,13 @@
   if (C99orCXXorObjC)
     getCurScope()->decrementMSManglingNumber();
 
+  MisleadingIndentationChecker MIChecker(*this, MSK_for, ForLoc);
+
   // Read the body statement.
   StmtResult Body(ParseStatement(TrailingElseLoc));
 
+  MIChecker.Check(Body.isUsable());
+
   // Pop the body scope if needed.
   InnerScope.Exit();
 
Index: clang/lib/StaticAnalyzer/Checkers/MallocChecker.cpp
===================================================================
--- clang/lib/StaticAnalyzer/Checkers/MallocChecker.cpp
+++ clang/lib/StaticAnalyzer/Checkers/MallocChecker.cpp
@@ -2525,19 +2525,18 @@
 
     // Find the most recent expression bound to the symbol in the current
     // context.
-      if (!ReferenceRegion) {
-        if (const MemRegion *MR = C.getLocationRegionIfPostStore(N)) {
-          SVal Val = State->getSVal(MR);
-          if (Val.getAsLocSymbol() == Sym) {
-            const VarRegion* VR = MR->getBaseRegion()->getAs<VarRegion>();
-            // Do not show local variables belonging to a function other than
-            // where the error is reported.
-            if (!VR ||
-                (VR->getStackFrame() == LeakContext->getStackFrame()))
-              ReferenceRegion = MR;
-          }
+    if (!ReferenceRegion) {
+      if (const MemRegion *MR = C.getLocationRegionIfPostStore(N)) {
+        SVal Val = State->getSVal(MR);
+        if (Val.getAsLocSymbol() == Sym) {
+          const VarRegion *VR = MR->getBaseRegion()->getAs<VarRegion>();
+          // Do not show local variables belonging to a function other than
+          // where the error is reported.
+          if (!VR || (VR->getStackFrame() == LeakContext->getStackFrame()))
+            ReferenceRegion = MR;
         }
       }
+    }
 
     // Allocation node, is the last node in the current or parent context in
     // which the symbol was tracked.
Index: clang/test/Index/pragma-diag-reparse.c
===================================================================
--- clang/test/Index/pragma-diag-reparse.c
+++ clang/test/Index/pragma-diag-reparse.c
@@ -11,6 +11,7 @@
   return x;
 }
 
+#pragma clang diagnostic ignored "-Wmisleading-indentation"
 void foo() { int b=0; while (b==b); }
 
 // RUN: env CINDEXTEST_EDITING=1 CINDEXTEST_FAILONERROR=1 c-index-test -test-load-source-reparse 5 local \
Index: clang/test/Misc/warning-wall.c
===================================================================
--- clang/test/Misc/warning-wall.c
+++ clang/test/Misc/warning-wall.c
@@ -90,6 +90,7 @@
 CHECK-NEXT:    -Wdangling-else
 CHECK-NEXT:  -Wswitch
 CHECK-NEXT:  -Wswitch-bool
+CHECK-NEXT:  -Wmisleading-indentation
 
 
 CHECK-NOT:-W
Index: clang/test/Preprocessor/pragma_diagnostic_sections.cpp
===================================================================
--- clang/test/Preprocessor/pragma_diagnostic_sections.cpp
+++ clang/test/Preprocessor/pragma_diagnostic_sections.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -Wall -Wunused-macros -Wunused-parameter -Wno-uninitialized -verify %s
+// RUN: %clang_cc1 -fsyntax-only -Wall -Wunused-macros -Wunused-parameter -Wno-uninitialized -Wno-misleading-indentation -verify %s
 
 // rdar://8365684
 struct S {