Pass AutoFDO profiles to LTO backend.

--
PiperOrigin-RevId: 144841772
MOS_MIGRATED_REVID=144841772

3 files changed, 41 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/FdoSupport.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/FdoSupport.java
index 1e37bda60c..6a0b231914 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/FdoSupport.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/FdoSupport.java
@@ -702,6 +702,25 @@ public class FdoSupport {
   }
 
   /**
+   * Adds the AutoFDO profile path to the variable builder and returns the profile artifact.
+   * If AutoFDO is disabled, no build variable is added and returns null.
+   */
+  @ThreadSafe
+  public Artifact buildProfileForLtoBackend(FeatureConfiguration featureConfiguration,
+      CcToolchainFeatures.Variables.Builder buildVariables, RuleContext ruleContext) {
+    if (!featureConfiguration.isEnabled(CppRuleClasses.AUTOFDO)) {
+      return null;
+    }
+    buildVariables.addStringVariable("fdo_profile_path", getAutoProfilePath(
+        fdoProfile, fdoRootExecPath).getPathString());
+    Artifact artifact = ruleContext.getAnalysisEnvironment().getDerivedArtifact(
+        fdoPath.getRelative(getAutoProfileRootRelativePath(fdoProfile)), fdoRoot);
+    ruleContext.getAnalysisEnvironment().registerAction(
+        new FdoStubAction(ruleContext.getActionOwner(), artifact));
+    return artifact;
+  }
+
+  /**
    * Returns the path of the FDO output tree (relative to the execution root)
    * containing the .gcda profile files, or null if FDO is not enabled.
    */
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 05907badd8..1d2a25c9af 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
@@ -134,6 +134,11 @@ public final class LTOBackendArtifacts {
     // The input to the LTO backend step is the bitcode file.
     buildVariablesBuilder.addStringVariable(
         "thinlto_input_bitcode_file", bitcodeFile.getExecPath().toString());
+    Artifact autoFdoProfile = CppHelper.getFdoSupport(ruleContext).buildProfileForLtoBackend(
+        featureConfiguration, buildVariablesBuilder, ruleContext);
+    if (autoFdoProfile != null) {
+      builder.addInput(autoFdoProfile);
+    }
     Variables buildVariables = buildVariablesBuilder.build();
     List<String> execArgs = new ArrayList<>();
     execArgs.addAll(featureConfiguration.getCommandLine("lto-backend", buildVariables));
diff --git a/src/test/java/com/google/devtools/build/lib/packages/util/MockCcSupport.java b/src/test/java/com/google/devtools/build/lib/packages/util/MockCcSupport.java
index 5c4bb7622f..f9969d1db0 100644
--- a/src/test/java/com/google/devtools/build/lib/packages/util/MockCcSupport.java
+++ b/src/test/java/com/google/devtools/build/lib/packages/util/MockCcSupport.java
@@ -234,6 +234,23 @@ public abstract class MockCcSupport {
           + "  }"
           + "}";
 
+  public static final String AUTO_FDO_CONFIGURATION =
+      ""
+          + "feature {"
+          + "  name: 'autofdo'"
+          + "  provides: 'profile'"
+          + "  flag_set {"
+          + "    action: 'c-compile'"
+          + "    action: 'c++-compile'"
+          + "    action: 'lto-backend'"
+          + "    expand_if_all_available: 'fdo_profile_path'"
+          + "    flag_group {"
+          + "      flag: '-fauto-profile=%{fdo_profile_path}'"
+          + "      flag: '-fprofile-correction'"
+          + "    }"
+          + "  }"
+          + "}";
+
   public static final String FDO_INSTRUMENT_CONFIGURATION =
       ""
           + "feature { "