Compile conditional statement and expressions.

--
MOS_MIGRATED_REVID=107385205

2 files changed, 93 insertions, 1 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/syntax/ConditionalExpression.java b/src/main/java/com/google/devtools/build/lib/syntax/ConditionalExpression.java
index 652baa6555..be83c3144c 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/ConditionalExpression.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/ConditionalExpression.java
@@ -11,9 +11,22 @@
 // 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.syntax;
 
+import static com.google.devtools.build.lib.syntax.compiler.ByteCodeUtils.append;
+
+import com.google.devtools.build.lib.syntax.compiler.ByteCodeUtils;
+import com.google.devtools.build.lib.syntax.compiler.DebugInfo;
+import com.google.devtools.build.lib.syntax.compiler.Jump;
+import com.google.devtools.build.lib.syntax.compiler.Jump.PrimitiveComparison;
+import com.google.devtools.build.lib.syntax.compiler.LabelAdder;
+import com.google.devtools.build.lib.syntax.compiler.VariableScope;
+
+import net.bytebuddy.implementation.bytecode.ByteCodeAppender;
+
+import java.util.ArrayList;
+import java.util.List;
+
 /**
  * Syntax node for an if/else expression.
  */
@@ -67,4 +80,29 @@ public final class ConditionalExpression extends Expression {
     thenCase.validate(env);
     elseCase.validate(env);
   }
+
+  @Override
+  ByteCodeAppender compile(VariableScope scope, DebugInfo debugInfo) throws EvalException {
+    List<ByteCodeAppender> code = new ArrayList<>();
+    LabelAdder afterLabel = new LabelAdder();
+    LabelAdder elseLabel = new LabelAdder();
+    // compile condition and convert to boolean
+    code.add(condition.compile(scope, debugInfo));
+    append(
+        code,
+        EvalUtils.toBoolean,
+        // jump to else block if false
+        Jump.ifIntOperandToZero(PrimitiveComparison.EQUAL).to(elseLabel));
+    // otherwise evaluate the expression for "then" and jump to end
+    code.add(thenCase.compile(scope, debugInfo));
+    append(
+        code,
+        Jump.to(afterLabel),
+        // add label for "else" and evaluate the expression
+        elseLabel);
+    code.add(elseCase.compile(scope, debugInfo));
+    append(code, afterLabel);
+
+    return ByteCodeUtils.compoundAppender(code);
+  }
 }
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/IfStatement.java b/src/main/java/com/google/devtools/build/lib/syntax/IfStatement.java
index ffe29479bd..a40a4daf37 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/IfStatement.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/IfStatement.java
@@ -13,9 +13,22 @@
 // limitations under the License.
 package com.google.devtools.build.lib.syntax;
 
+import static com.google.devtools.build.lib.syntax.compiler.ByteCodeUtils.append;
+
+import com.google.common.base.Optional;
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
+import com.google.devtools.build.lib.syntax.compiler.ByteCodeUtils;
+import com.google.devtools.build.lib.syntax.compiler.DebugInfo;
+import com.google.devtools.build.lib.syntax.compiler.Jump;
+import com.google.devtools.build.lib.syntax.compiler.Jump.PrimitiveComparison;
+import com.google.devtools.build.lib.syntax.compiler.LabelAdder;
+import com.google.devtools.build.lib.syntax.compiler.LoopLabels;
+import com.google.devtools.build.lib.syntax.compiler.VariableScope;
+
+import net.bytebuddy.implementation.bytecode.ByteCodeAppender;
 
+import java.util.ArrayList;
 import java.util.List;
 
 /**
@@ -66,6 +79,17 @@ public final class IfStatement extends Statement {
       condition.validate(env);
       validateStmts(env, stmts);
     }
+
+    @Override
+    ByteCodeAppender compile(
+        VariableScope scope, Optional<LoopLabels> loopLabels, DebugInfo debugInfo)
+            throws EvalException {
+      List<ByteCodeAppender> code = new ArrayList<>();
+      for (Statement statement : stmts) {
+        code.add(statement.compile(scope, loopLabels, debugInfo));
+      }
+      return ByteCodeUtils.compoundAppender(code);
+    }
   }
 
   private final ImmutableList<ConditionalStatements> thenBlocks;
@@ -132,4 +156,34 @@ public final class IfStatement extends Statement {
     }
     env.finishTemporarilyDisableReadonlyCheckBranch();
   }
+
+  @Override
+  ByteCodeAppender compile(
+      VariableScope scope, Optional<LoopLabels> loopLabels, DebugInfo debugInfo)
+          throws EvalException {
+    List<ByteCodeAppender> code = new ArrayList<>();
+    LabelAdder after = new LabelAdder();
+    LabelAdder nextConditionalOrElse;
+    for (ConditionalStatements statement : thenBlocks) {
+      nextConditionalOrElse = new LabelAdder();
+      // compile condition and convert to boolean
+      code.add(statement.getCondition().compile(scope, debugInfo));
+      append(
+          code,
+          EvalUtils.toBoolean,
+          // jump to next conditional/else block if false
+          Jump.ifIntOperandToZero(PrimitiveComparison.EQUAL).to(nextConditionalOrElse));
+      // otherwise execute the body and jump to end
+      code.add(statement.compile(scope, loopLabels, debugInfo));
+      append(code, Jump.to(after));
+      // add label for next conditional or the else block (which may be empty, but no matter)
+      append(code, nextConditionalOrElse);
+    }
+    for (Statement statement : elseBlock) {
+      code.add(statement.compile(scope, loopLabels, debugInfo));
+    }
+    append(code, after);
+
+    return ByteCodeUtils.compoundAppender(code);
+  }
 }