python: Flush the simulation stdout/stderr buffers

Occasionally gem5's stdout/stderr, when run within the TestLib
framework, will be shuffled. This is resolved by flushing the
stdout/stderr buffer before and after simulation.

In addition to this, the verifier.py has been improved to remove
boilerplate gem5 code from the stdout comparison.

Change-Id: I04c8f9cee4475b8eab2f1ba9bb76bfa3cfcca6ec
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/34995
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/python/m5/simulate.py

@@ -175,7 +175,15 @@ def simulate(*args, **kwargs):
     if _drain_manager.isDrained():
         _drain_manager.resume()
 
-    return _m5.event.simulate(*args, **kwargs)
+    # We flush stdout and stderr before and after the simulation to ensure the
+    # output arrive in order.
+    sys.stdout.flush()
+    sys.stderr.flush()
+    sim_out = _m5.event.simulate(*args, **kwargs)
+    sys.stdout.flush()
+    sys.stderr.flush()
+
+    return sim_out
 
 def drain():
     """Drain the simulator in preparation of a checkpoint or memory mode

tests/gem5/cpu_tests/ref/Bubblesort

@@ -1,6 +1,2 @@
-gem5 Simulator System.  http://gem5.org
-gem5 is copyrighted software; use the --copyright option for details.
-
-
 Global frequency set at 1000000000000 ticks per second
 -50000

tests/gem5/cpu_tests/ref/FloatMM

@@ -1,6 +1,2 @@
-gem5 Simulator System.  http://gem5.org
-gem5 is copyrighted software; use the --copyright option for details.
-
-
 Global frequency set at 1000000000000 ticks per second
 -776.000061

tests/gem5/dram-lowp/ref/simout

@@ -1,7 +1,3 @@
-gem5 Simulator System.  http://gem5.org
-gem5 is copyrighted software; use the --copyright option for details.
-
-
 Global frequency set at 1000000000000 ticks per second
 --- Done DRAM low power sweep ---
 Fixed params - 

tests/gem5/hello_se/ref/simout

@@ -1,7 +1,3 @@
-gem5 Simulator System.  http://gem5.org
-gem5 is copyrighted software; use the --copyright option for details.
-
-
 Global frequency set at 1000000000000 ticks per second
 **** REAL SIMULATION ****
 Hello world!

tests/gem5/insttest_se/ref/sparc/linux/insttest/simout

@@ -1,7 +1,3 @@
-gem5 Simulator System.  http://gem5.org
-gem5 is copyrighted software; use the --copyright option for details.
-
-
 Global frequency set at 1000000000000 ticks per second
 **** REAL SIMULATION ****
 Begining test of difficult SPARC instructions...

tests/gem5/learning_gem5/ref/hello

@@ -1,7 +1,3 @@
-gem5 Simulator System.  http://gem5.org
-gem5 is copyrighted software; use the --copyright option for details.
-
-
 Global frequency set at 1000000000000 ticks per second
 Beginning simulation!
 Hello world!

tests/gem5/learning_gem5/ref/hello_goodbye

@@ -1,7 +1,3 @@
-gem5 Simulator System.  http://gem5.org
-gem5 is copyrighted software; use the --copyright option for details.
-
-
 Global frequency set at 1000000000000 ticks per second
 Beginning simulation!
 Exiting @ tick 10944163 because Goodbye hello!! Goodbye hello!! Goodbye hello!! Goodbye hello!! Goodbye hello!! Goodbye hello!! Goo

tests/gem5/learning_gem5/ref/simple

@@ -1,7 +1,3 @@
-gem5 Simulator System.  http://gem5.org
-gem5 is copyrighted software; use the --copyright option for details.
-
-
 Global frequency set at 1000000000000 ticks per second
 Hello World! From a SimObject!
 Beginning simulation!

tests/gem5/learning_gem5/ref/test

@@ -1,7 +1,3 @@
-gem5 Simulator System.  http://gem5.org
-gem5 is copyrighted software; use the --copyright option for details.
-
-
 Global frequency set at 1000000000 ticks per second
 Beginning simulation!
 Exiting @ tick 9981 because Ruby Tester completed

tests/gem5/learning_gem5/ref/threads

@@ -1,7 +1,3 @@
-gem5 Simulator System.  http://gem5.org
-gem5 is copyrighted software; use the --copyright option for details.
-
-
 Global frequency set at 1000000000000 ticks per second
 Beginning simulation!
 Running on 2 cores. with 100 values

tests/gem5/m5threads_test_atomic/ref/sparc64/simout

@@ -1,7 +1,3 @@
-gem5 Simulator System.  http://gem5.org
-gem5 is copyrighted software; use the --copyright option for details.
-
-
 Global frequency set at 1000000000000 ticks per second
 Init done
 [Iteration 1, Thread 1] Got lock

tests/gem5/verifier.py

@@ -115,6 +115,9 @@ class DerivedGoldStandard(MatchGoldStandard):
 class MatchStdout(DerivedGoldStandard):
     _file = constants.gem5_simulation_stdout
     _default_ignore_regex = [
+            re.compile('^\s+$'), # Remove blank lines.
+            re.compile('^gem5 Simulator System'),
+            re.compile('^gem5 is copyrighted software'),
             re.compile('^Redirecting (stdout|stderr) to'),
             re.compile('^gem5 version '),
             re.compile('^gem5 compiled '),