Index: llvm/trunk/docs/CommandGuide/llvm-exegesis.rst
===================================================================
--- llvm/trunk/docs/CommandGuide/llvm-exegesis.rst
+++ llvm/trunk/docs/CommandGuide/llvm-exegesis.rst
@@ -190,7 +190,9 @@
 
 .. option:: -mode=[latency|uops|inverse_throughput|analysis]
 
- Specify the run mode.
+ Specify the run mode. Note that if you pick `analysis` mode, you also need
+ to specify at least one of the `-analysis-clusters-output-file=` and
+ `-analysis-inconsistencies-output-file=`.
 
 .. option:: -num-repetitions=<Number of repetition>
 
@@ -205,12 +207,12 @@
 .. option:: -analysis-clusters-output-file=</path/to/file>
 
  If provided, write the analysis clusters as CSV to this file. "-" prints to
- stdout.
+ stdout. By default, this analysis is not run.
 
 .. option:: -analysis-inconsistencies-output-file=</path/to/file>
 
  If non-empty, write inconsistencies found during analysis to this file. `-`
- prints to stdout.
+ prints to stdout. By default, this analysis is not run.
 
 .. option:: -analysis-numpoints=<dbscan numPoints parameter>
 
Index: llvm/trunk/test/tools/llvm-exegesis/X86/analysis-uops-backwards.test
===================================================================
--- llvm/trunk/test/tools/llvm-exegesis/X86/analysis-uops-backwards.test
+++ llvm/trunk/test/tools/llvm-exegesis/X86/analysis-uops-backwards.test
@@ -1,5 +1,5 @@
 # This tests backwards-compatibility of the yaml schema (see PR39082).
-# RUN: llvm-exegesis -mode=analysis -benchmarks-file=%s -analysis-inconsistencies-output-file="" -analysis-numpoints=1 | FileCheck %s
+# RUN: llvm-exegesis -mode=analysis -benchmarks-file=%s -analysis-clusters-output-file=- -analysis-numpoints=1 | FileCheck %s
 
 # CHECK: cluster_id,opcode_name,config,sched_class,HWPort0,HWPort1,HWPort2,HWPort3,HWPort4,HWPort5,HWPort6,HWPort7,NumMicroOps
 # CHECK-NEXT: vzeroall
Index: llvm/trunk/test/tools/llvm-exegesis/X86/analysis-uops-variant.test
===================================================================
--- llvm/trunk/test/tools/llvm-exegesis/X86/analysis-uops-variant.test
+++ llvm/trunk/test/tools/llvm-exegesis/X86/analysis-uops-variant.test
@@ -1,4 +1,4 @@
-# RUN: llvm-exegesis -mode=analysis -benchmarks-file=%s -analysis-inconsistencies-output-file="" -analysis-numpoints=1 | FileCheck %s
+# RUN: llvm-exegesis -mode=analysis -benchmarks-file=%s -analysis-clusters-output-file=- -analysis-numpoints=1 | FileCheck %s
 
 # REQUIRES: asserts
 # (sched class name is NDEBUG only)
Index: llvm/trunk/test/tools/llvm-exegesis/X86/analysis-uops.test
===================================================================
--- llvm/trunk/test/tools/llvm-exegesis/X86/analysis-uops.test
+++ llvm/trunk/test/tools/llvm-exegesis/X86/analysis-uops.test
@@ -1,4 +1,4 @@
-# RUN: llvm-exegesis -mode=analysis -benchmarks-file=%s -analysis-inconsistencies-output-file="" -analysis-numpoints=1 | FileCheck %s
+# RUN: llvm-exegesis -mode=analysis -benchmarks-file=%s -analysis-clusters-output-file=- -analysis-numpoints=1 | FileCheck %s
 
 # CHECK: cluster_id,opcode_name,config,sched_class,HWPort0,HWPort1,HWPort2,HWPort3,HWPort4,HWPort5,HWPort6,HWPort7,NumMicroOps
 # CHECK-NEXT: vzeroall
Index: llvm/trunk/tools/llvm-exegesis/llvm-exegesis.cpp
===================================================================
--- llvm/trunk/tools/llvm-exegesis/llvm-exegesis.cpp
+++ llvm/trunk/tools/llvm-exegesis/llvm-exegesis.cpp
@@ -91,10 +91,10 @@
 
 static cl::opt<std::string>
     AnalysisClustersOutputFile("analysis-clusters-output-file", cl::desc(""),
-                               cl::init("-"));
+                               cl::init(""));
 static cl::opt<std::string>
     AnalysisInconsistenciesOutputFile("analysis-inconsistencies-output-file",
-                                      cl::desc(""), cl::init("-"));
+                                      cl::desc(""), cl::init(""));
 
 static cl::opt<std::string>
     CpuName("mcpu",
@@ -404,6 +404,13 @@
   if (BenchmarkFile.empty())
     llvm::report_fatal_error("--benchmarks-file must be set.");
 
+  if (AnalysisClustersOutputFile.empty() &&
+      AnalysisInconsistenciesOutputFile.empty()) {
+    llvm::report_fatal_error(
+        "At least one of --analysis-clusters-output-file and "
+        "--analysis-inconsistencies-output-file must be specified.");
+  }
+
   llvm::InitializeNativeTarget();
   llvm::InitializeNativeTargetAsmPrinter();
   llvm::InitializeNativeTargetDisassembler();