Allow rules and targets to specify extra execution platform constraints.

RuleClass.Builder now allows authors to specify whether a rule's targets
can add additional constraints on the execution platform, and to declare
additional constraints for all targets of that rule.

Targets which support this now have an attribute,
"exec_compatible_with", which supports specifying additional constraints
that the execution platform used must match.

This attribute is non-configurable. It will only affect execution
platforms used during toolchain resolution.

Part of #5217.

Change-Id: Id2400dbf869a00aa2be3e3d2f085c2850cd6dc00

Closes #5227.

Change-Id: If7d55f08f7f44bc7d7f6dfec86a3e6bcd68574b9
PiperOrigin-RevId: 199326255

1 files changed, 26 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/ConfiguredTargetFunction.java b/src/main/java/com/google/devtools/build/lib/skyframe/ConfiguredTargetFunction.java
index 8363ff7144..f1df1166bc 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/ConfiguredTargetFunction.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/ConfiguredTargetFunction.java
@@ -31,6 +31,7 @@ import com.google.devtools.build.lib.analysis.ConfiguredTarget;
 import com.google.devtools.build.lib.analysis.ConfiguredTargetFactory;
 import com.google.devtools.build.lib.analysis.Dependency;
 import com.google.devtools.build.lib.analysis.DependencyResolver.InconsistentAspectOrderException;
+import com.google.devtools.build.lib.analysis.PlatformSemantics;
 import com.google.devtools.build.lib.analysis.TargetAndConfiguration;
 import com.google.devtools.build.lib.analysis.ToolchainContext;
 import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
@@ -57,9 +58,11 @@ import com.google.devtools.build.lib.packages.Attribute;
 import com.google.devtools.build.lib.packages.BuildType;
 import com.google.devtools.build.lib.packages.NoSuchTargetException;
 import com.google.devtools.build.lib.packages.NoSuchThingException;
+import com.google.devtools.build.lib.packages.NonconfigurableAttributeMapper;
 import com.google.devtools.build.lib.packages.Package;
 import com.google.devtools.build.lib.packages.RawAttributeMapper;
 import com.google.devtools.build.lib.packages.Rule;
+import com.google.devtools.build.lib.packages.RuleClass.ExecutionPlatformConstraintsAllowed;
 import com.google.devtools.build.lib.packages.RuleClassProvider;
 import com.google.devtools.build.lib.packages.RuleTransitionFactory;
 import com.google.devtools.build.lib.packages.Target;
@@ -272,11 +275,15 @@ public final class ConfiguredTargetFunction implements SkyFunction {
         if (rule.getRuleClassObject().supportsPlatforms()) {
           ImmutableSet<Label> requiredToolchains =
               rule.getRuleClassObject().getRequiredToolchains();
+
+          // Collect local (target, rule) constraints for filtering out execution platforms.
+          ImmutableSet<Label> execConstraintLabels = getExecutionPlatformConstraints(rule);
           toolchainContext =
               ToolchainUtil.createToolchainContext(
                   env,
                   rule.toString(),
                   requiredToolchains,
+                  execConstraintLabels,
                   configuredTargetKey.getConfigurationKey());
           if (env.valuesMissing()) {
             return null;
@@ -384,6 +391,25 @@ public final class ConfiguredTargetFunction implements SkyFunction {
   }
 
   /**
+   * Returns the target-specific execution platform constraints, based on the rule definition and
+   * any constraints added by the target.
+   */
+  private static ImmutableSet<Label> getExecutionPlatformConstraints(Rule rule) {
+    NonconfigurableAttributeMapper mapper = NonconfigurableAttributeMapper.of(rule);
+    ImmutableSet.Builder<Label> execConstraintLabels = new ImmutableSet.Builder<>();
+
+    execConstraintLabels.addAll(rule.getRuleClassObject().getExecutionPlatformConstraints());
+
+    if (rule.getRuleClassObject().executionPlatformConstraintsAllowed()
+        == ExecutionPlatformConstraintsAllowed.PER_TARGET) {
+      execConstraintLabels.addAll(
+          mapper.get(PlatformSemantics.EXEC_COMPATIBLE_WITH_ATTR, BuildType.LABEL_LIST));
+    }
+
+    return execConstraintLabels.build();
+  }
+
+  /**
    * Computes the direct dependencies of a node in the configured target graph (a configured target
    * or an aspects).
    *