Use Blaze's CommandLine infrastructure to expand ThinLTO command line…

…s only when necessary to avoid unnecessary memory consumption

RELNOTES: None.
PiperOrigin-RevId: 251819397

src/main/java/com/google/devtools/build/lib/rules/cpp/LtoBackendArtifacts.java

@@ -17,6 +17,7 @@
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableSet;
 import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.actions.CommandLine;
 import com.google.devtools.build.lib.analysis.actions.ActionConstructionContext;
 import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
 import com.google.devtools.build.lib.analysis.config.BuildOptions;
@@ -29,7 +30,6 @@
 import com.google.devtools.build.lib.rules.cpp.CppLinkAction.LinkArtifactFactory;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
 import com.google.devtools.build.lib.vfs.PathFragment;
-import java.util.ArrayList;
 import java.util.List;
 import java.util.Objects;
 import javax.annotation.Nullable;
@@ -289,18 +289,9 @@ private void scheduleLtoBackendAction(
  builder.setExecutable(compiler);
  }
 
- List<String> execArgs = new ArrayList<>();
- execArgs.addAll(
- CppHelper.getCommandLine(
- ruleErrorConsumer, featureConfiguration, buildVariables, CppActionNames.LTO_BACKEND));
- // If this is a PIC compile (set based on the CppConfiguration), the PIC
- // option should be added after the rest of the command line so that it
- // cannot be overridden. This is consistent with the ordering in the
- // CppCompileAction's compiler options.
- if (usePic) {
- execArgs.add("-fPIC");
- }
- builder.addExecutableArguments(execArgs);
+ CommandLine ltoCommandLine =
+ new LtoBackendCommandLine(featureConfiguration, buildVariables, usePic);
+ builder.addCommandLine(ltoCommandLine);
 
  actionConstructionContext.registerAction(builder.build(actionConstructionContext));
  }

src/main/java/com/google/devtools/build/lib/rules/cpp/LtoBackendCommandLine.java

@@ -0,0 +1,60 @@
+// Copyright 2019 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.devtools.build.lib.rules.cpp;
+
+import com.google.common.collect.ImmutableList;
+import com.google.devtools.build.lib.actions.CommandLine;
+import com.google.devtools.build.lib.actions.CommandLineExpansionException;
+import com.google.devtools.build.lib.rules.cpp.CcToolchainFeatures.ExpansionException;
+import com.google.devtools.build.lib.rules.cpp.CcToolchainFeatures.FeatureConfiguration;
+
+/**
+ * A representation of command line for {@link LtoBackendAction}.
+ *
+ * <p>We have this class so we're able to defer construction of the command line to execution phase.
+ */
+public class LtoBackendCommandLine extends CommandLine {
+
+ private final FeatureConfiguration featureConfiguration;
+ private final CcToolchainVariables buildVariables;
+ private final boolean usePic;
+
+ LtoBackendCommandLine(
+ FeatureConfiguration featureConfiguration,
+ CcToolchainVariables ccToolchainVariables,
+ boolean usePic) {
+ this.featureConfiguration = featureConfiguration;
+ this.buildVariables = ccToolchainVariables;
+ this.usePic = usePic;
+ }
+
+ @Override
+ public Iterable<String> arguments() throws CommandLineExpansionException {
+ ImmutableList.Builder<String> args = ImmutableList.builder();
+ try {
+ args.addAll(featureConfiguration.getCommandLine(CppActionNames.LTO_BACKEND, buildVariables));
+ } catch (ExpansionException e) {
+ throw new CommandLineExpansionException(e.getMessage());
+ }
+ // If this is a PIC compile (set based on the CppConfiguration), the PIC
+ // option should be added after the rest of the command line so that it
+ // cannot be overridden. This is consistent with the ordering in the
+ // CppCompileAction's compiler options.
+ if (usePic) {
+ args.add("-fPIC");
+ }
+ return args.build();
+ }
+}