[XRay][compiler-rt] Reduce XRay log spam

This change makes XRay print the log file output only when the verbosity
level is higher than 0. It reduces the log spam in the default case when
we want XRay running silently, except when there are actual
fatal/serious errors.

We also update the documentation to show how to get the information
after the change to the default behaviour.

llvm-svn: 320550

compiler-rt/lib/xray/xray_utils.cc

@@ -117,7 +117,8 @@ int getLogFD() XRAY_NEVER_INSTRUMENT {
            TmpFilename);
     return -1;
   }
-  Report("XRay: Log file in '%s'\n", TmpFilename);
+  if (__sanitizer::Verbosity())
+    Report("XRay: Log file in '%s'\n", TmpFilename);
 
   return Fd;
 }

llvm/docs/XRay.rst

@@ -164,6 +164,9 @@ variable, where we list down the options and their defaults below.
 |                   |                 |               | Data Recorder          |
 |                   |                 |               | (FDR) mode.            |
 +-------------------+-----------------+---------------+------------------------+
+| verbosity         | ``int``         | ``0``         | Runtime verbosity      |
+|                   |                 |               | level.                 |
++-------------------+-----------------+---------------+------------------------+
 
 
 If you choose to not use the default logging implementation that comes with the

llvm/docs/XRayExample.rst

@@ -60,7 +60,7 @@ to enable XRay at application start. To do this, XRay checks the
   $ ./bin/llc input.ll
 
   # We need to set the XRAY_OPTIONS to enable some features.
-  $ XRAY_OPTIONS="patch_premain=true xray_mode=xray-basic" ./bin/llc input.ll
+  $ XRAY_OPTIONS="patch_premain=true xray_mode=xray-basic verbosity=1" ./bin/llc input.ll
   ==69819==XRay: Log file in 'xray-log.llc.m35qPB'
 
 At this point we now have an XRay trace we can start analysing.