Make .d file analysis properly mark used module (.pcm) files.

Previously, we thought this wouldn't be necessary, as a change in .pcm would
always be accompanied by a corresponding change in a header. However, in the
current compile module this isn't true. Modules currently require all
transitive modules as inputs even though they might not use a single header
from them. Thus, if a module //a depends on a module //b, any change to //b's
headers will currently require //a to be rebuilt unless those headers are
actually included by //a. This leads to false positive cache results.

--
MOS_MIGRATED_REVID=135134348

2 files changed, 3 insertions, 4 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppCompileAction.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppCompileAction.java
index 373574fe24..1d06026c93 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppCompileAction.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppCompileAction.java
@@ -813,8 +813,10 @@ public class CppCompileAction extends AbstractAction
     Set<PathFragment> declaredIncludeDirs = Sets.newHashSet(context.getDeclaredIncludeDirs());
     Set<PathFragment> warnIncludeDirs = Sets.newHashSet(context.getDeclaredIncludeWarnDirs());
     Set<Artifact> declaredIncludeSrcs = Sets.newHashSet(getDeclaredIncludeSrcs());
+    Set<Artifact> transitiveModules = Sets.newHashSet(context.getTransitiveModules(usePic));
     for (Artifact input : inputsForValidation) {
       if (context.getTransitiveCompilationPrerequisites().contains(input)
+          || transitiveModules.contains(input)
           || allowedIncludes.contains(input)) {
         continue; // ignore our fixed source in mandatoryInput: we just want includes
       }
@@ -1014,6 +1016,7 @@ public class CppCompileAction extends AbstractAction
     addToMap(allowedDerivedInputMap, mandatoryInputs);
     addToMap(allowedDerivedInputMap, getDeclaredIncludeSrcs());
     addToMap(allowedDerivedInputMap, context.getTransitiveCompilationPrerequisites());
+    addToMap(allowedDerivedInputMap, context.getTransitiveModules(usePic));
     Artifact artifact = getSourceFile();
     if (!artifact.isSourceArtifact()) {
       allowedDerivedInputMap.put(artifact.getExecPath(), artifact);
diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/HeaderDiscovery.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/HeaderDiscovery.java
index e80856b7c2..5b59a0601f 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/HeaderDiscovery.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/HeaderDiscovery.java
@@ -103,10 +103,6 @@ public class HeaderDiscovery {
     // Check inclusions.
     IncludeProblems problems = new IncludeProblems();
     for (Path execPath : depSet.getDependencies()) {
-      // Module .pcm files are generated and thus aren't declared inputs.
-      if (execPath.getBaseName().endsWith(".pcm")) {
-        continue;
-      }
       PathFragment execPathFragment = execPath.asFragment();
       if (execPathFragment.isAbsolute()) {
         // Absolute includes from system paths are ignored.