commit f718a4249739f63e3a0c6e008faa3c7d47fa30f9
author gregce <gregce@google.com> Tue Jun 04 14:45:32 2019 -0700
committer Copybara-Service <copybara-worker@google.com> Tue Jun 04 14:46:47 2019 -0700
tree e1adc41b1c84e62adf4b608e0b6bc676f9a17660
parent 7ac7723e09cf7e872f70c552217ca2e552ef5833

Fix performance regression with manual trimming.

When --enforce_transitive_configs_for_config_feature_flag=true
(which means manual trimming is enabled), the manual trimming
transition applies to every configured target in the build, even
though it's a no-op for most of them. But it unconditionally creates
new BuildOptions instances, each of which has its hash key computed
later in the build. This is expensive enough to severely harm
analysis time.

With this change, the transition returns the original instance when no
trimming is necessary.

Example results on a trivial android_binary depending on an android_library
with trimming:

Before:
############################################
# Original Blaze, manual trimming disabled:
b/blazedev_orig build --nobuild //testapp:binary --enforce_transitive_configs_for_config_feature_flag=false | sort | uniq -c
137 CALLING BuildOptions.maybeInitializeFingerprintAndHashCode

# Original Blaze, manual trimming enabled:
b/blazedev_orig build --nobuild //testapp:binary --enforce_transitive_configs_for_config_feature_flag=true | sort | uniq -c
809 CALLING BuildOptions.maybeInitializeFingerprintAndHashCode
573 TRIMMING TRANSITION RETURNED NEW BUILDOPTIONS INSTANCE
############################################

After:
############################################
# Updated Blaze, manual trimming disabled:
b/blazedev_new build --nobuild //testapp:binary --enforce_transitive_configs_for_config_feature_flag=false | sort | uniq -c
138 CALLING BuildOptions.maybeInitializeFingerprintAndHashCode

# Updated Blaze, manual trimming enabled:
b/blazedev_new build --nobuild //testapp:binary --enforce_transitive_configs_for_config_feature_flag=true | sort | uniq -c
475 CALLING BuildOptions.maybeInitializeFingerprintAndHashCode
209 TRIMMING TRANSITION RETURNED NEW BUILDOPTIONS INSTANCE
############################################

We still create more instances when manual trimming is on, but this is expected. Note that rules which don't use trimming (don't have the transitive_configs attribute) don't create *any* more instances.

PiperOrigin-RevId: 251520074