[NFC][exegesis] By default, don't dump objects to disk

[lebedev.ri]

Summary

It's a strictly-developer feature, which is useless most of the time.

[RKSimon]

Thanks for fixing this!

[lebedev.ri]

Thank you for the review!
I want to be explicit: i *do* think the feature is useful, and i *do* use it, but it's really specialized.

llvm/test/tools/llvm-exegesis/X86/latency/dump-object-to-disk.s

+# RUN: llvm-exegesis -mtriple=x86_64-unknown-unknown -mcpu=x86-64 -mode=latency --skip-measurements -opcode-name=ADDPSrr -repetition-mode=duplicate -dump-object-to-disk=1 2>&1 | FileCheck %s --check-prefix=CHECK-ON
+# RUN: llvm-exegesis -mtriple=x86_64-unknown-unknown -mcpu=x86-64 -mode=latency --skip-measurements -opcode-name=ADDPSrr -repetition-mode=loop      -dump-object-to-disk=1 2>&1 | FileCheck %s --check-prefix=CHECK-ON
+# RUN: llvm-exegesis -mtriple=x86_64-unknown-unknown -mcpu=x86-64 -mode=latency --skip-measurements -opcode-name=ADDPSrr -repetition-mode=duplicate -dump-object-to-disk=0 2>&1 | FileCheck %s --check-prefix=CHECK-OFF
+# RUN: llvm-exegesis -mtriple=x86_64-unknown-unknown -mcpu=x86-64 -mode=latency --skip-measurements -opcode-name=ADDPSrr -repetition-mode=loop      -dump-object-to-disk=0 2>&1 | FileCheck %s --check-prefix=CHECK-OFF
+# RUN: llvm-exegesis -mtriple=x86_64-unknown-unknown -mcpu=x86-64 -mode=latency --skip-measurements -opcode-name=ADDPSrr -repetition-mode=duplicate 2>&1 | FileCheck %s --check-prefix=CHECK-OFF
+# RUN: llvm-exegesis -mtriple=x86_64-unknown-unknown -mcpu=x86-64 -mode=latency --skip-measurements -opcode-name=ADDPSrr -repetition-mode=loop 2>&1 | FileCheck %s --check-prefix=CHECK-OFF
+
+CHECK-ON: Check generated assembly with
+CHECK-OFF-NOT: Check generated assembly with

llvm/tools/llvm-exegesis/llvm-exegesis.cpp

TripleName("mtriple",
                cl::desc("Target triple. See -version for available targets"),
                cl::cat(Options));
 
 static cl::opt<std::string>
     MCPU("mcpu",
          cl::desc("Target a specific cpu type (-mcpu=help for details)"),
          cl::value_desc("cpu-name"), cl::cat(Options), cl::init("native"));
 
-static cl::opt<bool>
-    DumpObjectToDisk("dump-object-to-disk",
-                     cl::desc("dumps the generated benchmark object to disk "
-                              "and prints a message to access it"),
-                     cl::cat(BenchmarkOptions), cl::init(true));
+static cl::opt<bool> DumpObjectToDisk(
+    "dump-object-to-disk",
+             "and prints a message to access it (default = false)"),
+    cl::cat(BenchmarkOptions), cl::init(false));
 
 static ExitOnError ExitOnErr("llvm-exegesis error: ");
 
 // Helper function that logs the error(s) and exits.
 template <typename... ArgTs> static void ExitWithError(ArgTs &&... Args) {
   ExitOnErr(make_error<Failure>(std::forward<ArgTs>(Args)...));
 }