Schedule LtoBackendAction when creating LtoBackendArtifact

There is no need to defer the action creation and scheduling, which
happens shortly thereafter, and just requires saving a bunch of information
on the LtoBackendArtifact.

This is preliminary restructuring that will aid some larger changes for
making tests that use static linking more efficient when built with ThinLTO
(for b/67424063).

RELNOTES: None
PiperOrigin-RevId: 174490283

2 files changed, 60 insertions, 39 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppLinkActionBuilder.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppLinkActionBuilder.java
index e5dd996fc2..091c9ac280 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppLinkActionBuilder.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppLinkActionBuilder.java
@@ -525,7 +525,9 @@ public class CppLinkActionBuilder {
   }
 
   private Iterable<LtoBackendArtifacts> createLtoArtifacts(
-      PathFragment ltoOutputRootPrefix, NestedSet<LibraryToLink> uniqueLibraries) {
+      PathFragment ltoOutputRootPrefix,
+      NestedSet<LibraryToLink> uniqueLibraries,
+      ImmutableSet<String> features) {
     Set<Artifact> compiled = new LinkedHashSet<>();
     for (LibraryToLink lib : uniqueLibraries) {
       compiled.addAll(lib.getLtoBitcodeFiles().keySet());
@@ -550,11 +552,25 @@ public class CppLinkActionBuilder {
       }
     }
 
+    List<String> argv = new ArrayList<>();
+    argv.addAll(toolchain.getLinkOptions());
+    argv.addAll(cppConfiguration.getCompilerOptions(features));
     ImmutableList.Builder<LtoBackendArtifacts> ltoOutputs = ImmutableList.builder();
     for (Artifact a : allBitcode.values()) {
       LtoBackendArtifacts ltoArtifacts =
           new LtoBackendArtifacts(
-              ltoOutputRootPrefix, a, allBitcode, ruleContext, configuration, linkArtifactFactory);
+              ltoOutputRootPrefix,
+              a,
+              allBitcode,
+              ruleContext,
+              configuration,
+              linkArtifactFactory,
+              featureConfiguration,
+              toolchain,
+              fdoSupport,
+              usePicForLtoBackendActions,
+              cppConfiguration.useFission(),
+              argv);
       ltoOutputs.add(ltoArtifacts);
     }
     return ltoOutputs.build();
@@ -672,7 +688,7 @@ public class CppLinkActionBuilder {
       // Use the originalUniqueLibraries which contains the full bitcode files
       // needed by the LTO backends (as opposed to the minimized bitcode files
       // that can be used by the LTO indexing step).
-      allLtoArtifacts = createLtoArtifacts(ltoOutputRootPrefix, originalUniqueLibraries);
+      allLtoArtifacts = createLtoArtifacts(ltoOutputRootPrefix, originalUniqueLibraries, features);
     }
 
     @Nullable Artifact thinltoParamFile = null;
@@ -864,23 +880,6 @@ public class CppLinkActionBuilder {
         renamedNonLibraryInputs.add(renamed == null ? a : renamed);
       }
       expandedNonLibraryInputs = renamedNonLibraryInputs;
-    } else if (isLtoIndexing && allLtoArtifacts != null) {
-      for (LtoBackendArtifacts a : allLtoArtifacts) {
-        List<String> argv = new ArrayList<>();
-        argv.addAll(toolchain.getLinkOptions());
-        argv.addAll(cppConfiguration.getCompilerOptions(features));
-        a.setCommandLine(argv);
-
-        a.scheduleLtoBackendAction(
-            ruleContext,
-            featureConfiguration,
-            toolchain,
-            fdoSupport,
-            usePicForLtoBackendActions,
-            cppConfiguration.useFission(),
-            configuration,
-            linkArtifactFactory);
-      }
     }
 
     // getPrimaryInput returns the first element, and that is a public interface - therefore the
diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/LtoBackendArtifacts.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/LtoBackendArtifacts.java
index 6c714c560a..a968ccbd8d 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/LtoBackendArtifacts.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/LtoBackendArtifacts.java
@@ -61,22 +61,19 @@ public final class LtoBackendArtifacts {
   // The result of executing the above command line, an ELF object file.
   private final Artifact objectFile;
 
-  // A map of all of the bitcode files. This is the universe from which the .imports file
-  // distills its lists.  The map is the same across all LtoBackendArtifacts of a given
-  // binary.
-  private final Map<PathFragment, Artifact> bitcodeFiles;
-
-  // Command line arguments to apply to back-end compile action, typically from
-  // the feature configuration and user-provided linkopts.
-  private List<String> commandLine;
-
   LtoBackendArtifacts(
       PathFragment ltoOutputRootPrefix,
       Artifact bitcodeFile,
       Map<PathFragment, Artifact> allBitCodeFiles,
       RuleContext ruleContext,
       BuildConfiguration configuration,
-      CppLinkAction.LinkArtifactFactory linkArtifactFactory) {
+      CppLinkAction.LinkArtifactFactory linkArtifactFactory,
+      FeatureConfiguration featureConfiguration,
+      CcToolchainProvider ccToolchain,
+      FdoSupportProvider fdoSupport,
+      boolean usePic,
+      boolean generateDwo,
+      List<String> commandLine) {
     this.bitcodeFile = bitcodeFile;
     PathFragment obj = ltoOutputRootPrefix.getRelative(bitcodeFile.getRootRelativePath());
 
@@ -86,7 +83,17 @@ public final class LtoBackendArtifacts {
     index = linkArtifactFactory.create(
         ruleContext, configuration, FileSystemUtils.appendExtension(obj, ".thinlto.bc"));
 
-    bitcodeFiles = allBitCodeFiles;
+    scheduleLtoBackendAction(
+        ruleContext,
+        featureConfiguration,
+        ccToolchain,
+        fdoSupport,
+        usePic,
+        generateDwo,
+        configuration,
+        linkArtifactFactory,
+        commandLine,
+        allBitCodeFiles);
   }
 
   // Interface to create an LTO backend that does not perform any cross-module optimization.
@@ -95,14 +102,31 @@ public final class LtoBackendArtifacts {
       Artifact bitcodeFile,
       RuleContext ruleContext,
       BuildConfiguration configuration,
-      CppLinkAction.LinkArtifactFactory linkArtifactFactory) {
+      CppLinkAction.LinkArtifactFactory linkArtifactFactory,
+      FeatureConfiguration featureConfiguration,
+      CcToolchainProvider ccToolchain,
+      FdoSupportProvider fdoSupport,
+      boolean usePic,
+      boolean generateDwo,
+      List<String> commandLine) {
     this.bitcodeFile = bitcodeFile;
 
     PathFragment obj = ltoOutputRootPrefix.getRelative(bitcodeFile.getRootRelativePath());
     objectFile = linkArtifactFactory.create(ruleContext, configuration, obj);
     imports = null;
     index = null;
-    bitcodeFiles = null;
+
+    scheduleLtoBackendAction(
+        ruleContext,
+        featureConfiguration,
+        ccToolchain,
+        fdoSupport,
+        usePic,
+        generateDwo,
+        configuration,
+        linkArtifactFactory,
+        commandLine,
+        null);
   }
 
   public Artifact getObjectFile() {
@@ -118,11 +142,7 @@ public final class LtoBackendArtifacts {
     builder.add(index);
   }
 
-  public void setCommandLine(List<String> cmdLine) {
-    commandLine = cmdLine;
-  }
-
-  public void scheduleLtoBackendAction(
+  private void scheduleLtoBackendAction(
       RuleContext ruleContext,
       FeatureConfiguration featureConfiguration,
       CcToolchainProvider ccToolchain,
@@ -130,7 +150,9 @@ public final class LtoBackendArtifacts {
       boolean usePic,
       boolean generateDwo,
       BuildConfiguration configuration,
-      CppLinkAction.LinkArtifactFactory linkArtifactFactory) {
+      CppLinkAction.LinkArtifactFactory linkArtifactFactory,
+      List<String> commandLine,
+      Map<PathFragment, Artifact> bitcodeFiles) {
     LtoBackendAction.Builder builder = new LtoBackendAction.Builder();
 
     builder.addInput(bitcodeFile);