[XRay][compiler-rt] Switch default XRay 'patch_premain' to false

[dberris]

Summary

Currently, we assume that applications built with XRay would like to
have the instrumentation sleds patched before main starts. This patch
changes the default so that we do not patch the instrumentation sleds
before main. This default is more helpful for deploying applications in
environments where changing the current default is harder (i.e. on
remote machines, or work-pool-like systems).

This default (not to patch pre-main) makes it easier to selectively run
applications with XRay instrumentation enabled, than with the current
state.

compiler-rt/trunk/lib/xray/xray_flags.inc

 //===-- xray_flags.inc ------------------------------------------*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // XRay runtime flags.
 //
 //===----------------------------------------------------------------------===//
 #ifndef XRAY_FLAG
 #error "Define XRAY_FLAG prior to including this file!"
 #endif
 
-XRAY_FLAG(bool, patch_premain, true,
+XRAY_FLAG(bool, patch_premain, false,
           "Whether to patch instrumentation points before main.")
 XRAY_FLAG(bool, xray_naive_log, true,
           "Whether to install the naive log implementation.")
 XRAY_FLAG(const char *, xray_logfile_base, "xray-log.",
           "Filename base for the xray logfile.")
 XRAY_FLAG(bool, xray_fdr_log, false,
           "Whether to install the flight data recorder logging implementation.")

compiler-rt/trunk/test/xray/TestCases/Linux/argv0-log-file-name.cc

 // Check to make sure argv[0] is contained within the (randomised) XRay log file
 // name.
 
 // RUN: %clangxx_xray -std=c++11 %s -o %t
-// RUN: %run %t > xray.log.file.name 2>&1
+// RUN: XRAY_OPTIONS="patch_premain=true xray_naive_log=true" %run %t > xray.log.file.name 2>&1
 // RUN: ls | FileCheck xray.log.file.name
 // RUN: rm xray-log.* xray.log.file.name
 
 #include <cstdio>
 #include <libgen.h>
 
 [[clang::xray_always_instrument]] int main(int argc, char *argv[]) {
   printf("// CHECK: xray-log.%s.{{.*}}\n", basename(argv[0]));
 }

compiler-rt/trunk/test/xray/TestCases/Linux/fixedsize-logging.cc

 // Check to make sure that we have a log file with a fixed-size.
 
 // RUN: %clangxx_xray -std=c++11 %s -o %t
-// RUN: XRAY_OPTIONS="verbosity=1 xray_logfile_base=fixedsize-logging-" %run %t 2>&1 | FileCheck %s
+// RUN: XRAY_OPTIONS="patch_premain=true xray_naive_log=true verbosity=1 xray_logfile_base=fixedsize-logging-" %run %t 2>&1 | FileCheck %s
 //
 // After all that, clean up the output xray log.
 //
 // RUN: rm fixedsize-logging-*
 
 #include <cstdio>
 
 [[clang::xray_always_instrument]] void foo() {
   printf("foo() is always instrumented!");
 }
 
 int main() {
   // CHECK: XRay: Log file in 'fixedsize-logging-{{.*}}'
   foo();
   // CHECK: foo() is always instrumented!
 }

compiler-rt/trunk/test/xray/TestCases/Linux/optional-inmemory-log.cc

 // Make sure that we don't get the inmemory logging implementation enabled when
 // we turn it off via options.
 
 // RUN: %clangxx_xray -std=c++11 %s -o %t
-// RUN: XRAY_OPTIONS="verbosity=1 xray_naive_log=false xray_logfile_base=optional-inmemory-log.xray-" %run %t 2>&1 | FileCheck %s
+// RUN: XRAY_OPTIONS="patch_premain=true verbosity=1 xray_naive_log=false xray_logfile_base=optional-inmemory-log.xray-" %run %t 2>&1 | FileCheck %s
 //
 // Make sure we clean out the logs in case there was a bug.
 //
 // RUN: rm -f optional-inmemory-log.xray-*
 
 #include <cstdio>
 
 [[clang::xray_always_instrument]] void foo() {
   printf("foo() is always instrumented!");
 }
 
 int main() {
   // CHECK-NOT: XRay: Log file in 'optional-inmemory-log.xray-{{.*}}'
   foo();
   // CHECK: foo() is always instrumented!
 }

compiler-rt/trunk/test/xray/TestCases/Linux/pic_test.cc

 // Test to check if we handle pic code properly.
 
 // RUN: %clangxx_xray -fxray-instrument -std=c++11 -fpic %s -o %t
-// RUN: XRAY_OPTIONS="verbosity=1 xray_logfile_base=pic-test-logging-" %run %t 2>&1 | FileCheck %s
+// RUN: XRAY_OPTIONS="patch_premain=true verbosity=1 xray_logfile_base=pic-test-logging-" %run %t 2>&1 | FileCheck %s
 // After all that, clean up the output xray log.
 //
 // RUN: rm pic-test-logging-*
 
 #include <cstdio>
 
 [[clang::xray_always_instrument]]
 unsigned short foo (unsigned b);