diff --git a/clang/include/clang/StaticAnalyzer/Core/AnalyzerOptions.def b/clang/include/clang/StaticAnalyzer/Core/AnalyzerOptions.def
--- a/clang/include/clang/StaticAnalyzer/Core/AnalyzerOptions.def
+++ b/clang/include/clang/StaticAnalyzer/Core/AnalyzerOptions.def
@@ -336,6 +336,18 @@
     "might be modeled by the analyzer to never return NULL.",
     false)
 
+ANALYZER_OPTION(
+    bool, ShouldIgnoreBisonGeneratedFiles, "ignore-bison-generated-files",
+    "If enabled, any files containing the \"/* A Bison parser, made by\" "
+    "won't be analyzed.",
+    true)
+
+ANALYZER_OPTION(
+    bool, ShouldIgnoreFlexGeneratedFiles, "ignore-flex-generated-files",
+    "If enabled, any files containing the \"/* A lexical scanner generated by "
+    "flex\" won't be analyzed.",
+    true)
+
 //===----------------------------------------------------------------------===//
 // Unsigned analyzer options.
 //===----------------------------------------------------------------------===//
diff --git a/clang/lib/StaticAnalyzer/Frontend/AnalysisConsumer.cpp b/clang/lib/StaticAnalyzer/Frontend/AnalysisConsumer.cpp
--- a/clang/lib/StaticAnalyzer/Frontend/AnalysisConsumer.cpp
+++ b/clang/lib/StaticAnalyzer/Frontend/AnalysisConsumer.cpp
@@ -35,6 +35,7 @@
 #include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h"
 #include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
 #include "llvm/ADT/PostOrderIterator.h"
+#include "llvm/ADT/ScopeExit.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Path.h"
@@ -493,13 +494,11 @@
   }
 }
 
-static bool isBisonFile(ASTContext &C) {
+static bool fileContainsString(StringRef Substring, ASTContext &C) {
   const SourceManager &SM = C.getSourceManager();
   FileID FID = SM.getMainFileID();
   StringRef Buffer = SM.getBufferOrFake(FID).getBuffer();
-  if (Buffer.startswith("/* A Bison parser, made by"))
-    return true;
-  return false;
+  return Buffer.contains(Substring);
 }
 
 void AnalysisConsumer::runAnalysisOnTranslationUnit(ASTContext &C) {
@@ -546,38 +545,48 @@
 }
 
 void AnalysisConsumer::HandleTranslationUnit(ASTContext &C) {
-
   // Don't run the actions if an error has occurred with parsing the file.
   DiagnosticsEngine &Diags = PP.getDiagnostics();
   if (Diags.hasErrorOccurred() || Diags.hasFatalErrorOccurred())
     return;
 
-  if (isBisonFile(C)) {
+  // Explicitly destroy the PathDiagnosticConsumer.  This will flush its output.
+  // FIXME: This should be replaced with something that doesn't rely on
+  // side-effects in PathDiagnosticConsumer's destructor. This is required when
+  // used with option -disable-free.
+  const auto DiagFlusherScopeExit =
+      llvm::make_scope_exit([this] { Mgr.reset(); });
+
+  if (Opts->ShouldIgnoreBisonGeneratedFiles &&
+      fileContainsString("/* A Bison parser, made by", C)) {
     reportAnalyzerProgress("Skipping bison-generated file\n");
-  } else if (Opts->DisableAllCheckers) {
+    return;
+  }
 
-    // Don't analyze if the user explicitly asked for no checks to be performed
-    // on this file.
+  if (Opts->ShouldIgnoreFlexGeneratedFiles &&
+      fileContainsString("/* A lexical scanner generated by flex", C)) {
+    reportAnalyzerProgress("Skipping flex-generated file\n");
+    return;
+  }
+
+  // Don't analyze if the user explicitly asked for no checks to be performed
+  // on this file.
+  if (Opts->DisableAllCheckers) {
     reportAnalyzerProgress("All checks are disabled using a supplied option\n");
-  } else {
-    // Otherwise, just run the analysis.
-    runAnalysisOnTranslationUnit(C);
+    return;
   }
 
+  // Otherwise, just run the analysis.
+  runAnalysisOnTranslationUnit(C);
+
   // Count how many basic blocks we have not covered.
   NumBlocksInAnalyzedFunctions = FunctionSummaries.getTotalNumBasicBlocks();
   NumVisitedBlocksInAnalyzedFunctions =
       FunctionSummaries.getTotalNumVisitedBasicBlocks();
   if (NumBlocksInAnalyzedFunctions > 0)
     PercentReachableBlocks =
-      (FunctionSummaries.getTotalNumVisitedBasicBlocks() * 100) /
+        (FunctionSummaries.getTotalNumVisitedBasicBlocks() * 100) /
         NumBlocksInAnalyzedFunctions;
-
-  // Explicitly destroy the PathDiagnosticConsumer.  This will flush its output.
-  // FIXME: This should be replaced with something that doesn't rely on
-  // side-effects in PathDiagnosticConsumer's destructor. This is required when
-  // used with option -disable-free.
-  Mgr.reset();
 }
 
 AnalysisConsumer::AnalysisMode
diff --git a/clang/test/Analysis/analyzer-config.c b/clang/test/Analysis/analyzer-config.c
--- a/clang/test/Analysis/analyzer-config.c
+++ b/clang/test/Analysis/analyzer-config.c
@@ -83,6 +83,8 @@
 // CHECK-NEXT: exploration_strategy = unexplored_first_queue
 // CHECK-NEXT: faux-bodies = true
 // CHECK-NEXT: graph-trim-interval = 1000
+// CHECK-NEXT: ignore-bison-generated-files = true
+// CHECK-NEXT: ignore-flex-generated-files = true
 // CHECK-NEXT: inline-lambdas = true
 // CHECK-NEXT: ipa = dynamic-bifurcate
 // CHECK-NEXT: ipa-always-inline-size = 3
diff --git a/clang/test/Analysis/flexignore.c b/clang/test/Analysis/flexignore.c
new file mode 100644
--- /dev/null
+++ b/clang/test/Analysis/flexignore.c
@@ -0,0 +1,14 @@
+// RUN: %clang_analyze_cc1 -analyzer-checker=core,debug.ExprInspection -verify -DEXPECT_NO_DIAGNOSTICS %s
+// RUN: %clang_analyze_cc1 -analyzer-checker=core,debug.ExprInspection -verify=conditional %s \
+// RUN:    -analyzer-config ignore-flex-generated-files=false
+
+#ifdef EXPECT_NO_DIAGNOSTICS
+// expected-no-diagnostics
+#endif
+
+/* A lexical scanner generated by flex */
+
+void clang_analyzer_warnIfReached();
+void foo() {
+  clang_analyzer_warnIfReached(); // conditional-warning {{REACHABLE}}
+}
diff --git a/clang/test/Analysis/yaccignore.c b/clang/test/Analysis/yaccignore.c
--- a/clang/test/Analysis/yaccignore.c
+++ b/clang/test/Analysis/yaccignore.c
@@ -1,13 +1,14 @@
-/* A Bison parser, made by GNU Bison 1.875.  */
-
-// RUN: rm -rf %t.plist
-// RUN: %clang_analyze_cc1 -analyzer-checker=core -analyzer-output=plist -o %t.plist -verify %s
-// RUN: FileCheck --input-file=%t.plist %s
+// RUN: %clang_analyze_cc1 -analyzer-checker=core,debug.ExprInspection -verify -DEXPECT_NO_DIAGNOSTICS %s
+// RUN: %clang_analyze_cc1 -analyzer-checker=core,debug.ExprInspection -verify=conditional %s \
+// RUN:    -analyzer-config ignore-bison-generated-files=false
 
+#ifdef EXPECT_NO_DIAGNOSTICS
 // expected-no-diagnostics
-int foo() {
-  int *x = 0;
-  return *x; // no-warning
-}
+#endif
 
-// CHECK:   <key>diagnostics</key>
+/* A Bison parser, made by GNU Bison 1.875.  */
+
+void clang_analyzer_warnIfReached();
+void foo() {
+  clang_analyzer_warnIfReached(); // conditional-warning {{REACHABLE}}
+}