build: deprecate --enable-gprof builds and remove from CI

As gprof relies on instrumentation you rarely get useful data compared
to a real optimised build. Lets deprecate the build option and
simplify the CI configuration as a result.

Buglink: https://gitlab.com/qemu-project/qemu/-/issues/1338
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20230131094224.861621-1-alex.bennee@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>

.gitlab-ci.d/buildtest.yml

@@ -467,27 +467,16 @@ tsan-build:
     TARGETS: x86_64-softmmu ppc64-softmmu riscv64-softmmu x86_64-linux-user
     MAKE_CHECK_ARGS: bench V=1
 
-# gprof/gcov are GCC features
-build-gprof-gcov:
+# gcov is a GCC features
+gcov:
   extends: .native_build_job_template
   needs:
     job: amd64-ubuntu2004-container
+  timeout: 80m
   variables:
     IMAGE: ubuntu2004
-    CONFIGURE_ARGS: --enable-gprof --enable-gcov
+    CONFIGURE_ARGS: --enable-gcov
     TARGETS: aarch64-softmmu ppc64-softmmu s390x-softmmu x86_64-softmmu
-  artifacts:
-    expire_in: 1 days
-    paths:
-      - build
-
-check-gprof-gcov:
-  extends: .native_test_job_template
-  needs:
-    - job: build-gprof-gcov
-      artifacts: true
-  variables:
-    IMAGE: ubuntu2004
     MAKE_CHECK_ARGS: check
   after_script:
     - cd build

docs/about/deprecated.rst

@@ -20,6 +20,20 @@ they were first deprecated in the 2.10.0 release.
 What follows is a list of all features currently marked as
 deprecated.
 
+Build options
+-------------
+
+``gprof`` builds (since 8.0)
+''''''''''''''''''''''''''''
+
+The ``--enable-gprof`` configure setting relies on compiler
+instrumentation to gather its data which can distort the generated
+profile. As other non-instrumenting tools are available that give a
+more holistic view of the system with non-instrumented binaries we are
+deprecating the build option and no longer defend it in CI. The
+``--enable-gcov`` build option remains for analysis test case
+coverage.
+
 System emulator command line arguments
 --------------------------------------
 

meson.build

@@ -3805,7 +3805,12 @@ summary_info += {'memory allocator':  get_option('malloc')}
 summary_info += {'avx2 optimization': config_host_data.get('CONFIG_AVX2_OPT')}
 summary_info += {'avx512bw optimization': config_host_data.get('CONFIG_AVX512BW_OPT')}
 summary_info += {'avx512f optimization': config_host_data.get('CONFIG_AVX512F_OPT')}
-summary_info += {'gprof enabled':     get_option('gprof')}
+if get_option('gprof')
+  gprof_info = 'YES (deprecated)'
+else
+  gprof_info = get_option('gprof')
+endif
+summary_info += {'gprof':             gprof_info}
 summary_info += {'gcov':              get_option('b_coverage')}
 summary_info += {'thread sanitizer':  config_host.has_key('CONFIG_TSAN')}
 summary_info += {'CFI support':       get_option('cfi')}

meson_options.txt

@@ -320,7 +320,8 @@ option('debug_stack_usage', type: 'boolean', value: false,
 option('qom_cast_debug', type: 'boolean', value: false,
        description: 'cast debugging support')
 option('gprof', type: 'boolean', value: false,
-       description: 'QEMU profiling with gprof')
+       description: 'QEMU profiling with gprof',
+       deprecated: true)
 option('profiler', type: 'boolean', value: false,
        description: 'profiler support')
 option('slirp_smbd', type : 'feature', value : 'auto',