Class ComparisonCoalescingOperatorAsmGenerator

java.lang.Object

org.ek9lang.compiler.backend.jvm.AbstractAsmGenerator

org.ek9lang.compiler.backend.jvm.AbstractControlFlowAsmGenerator

org.ek9lang.compiler.backend.jvm.ComparisonCoalescingOperatorAsmGenerator

final class ComparisonCoalescingOperatorAsmGenerator
extends AbstractControlFlowAsmGenerator

Specialized generator for EK9 comparison coalescing operators (<?, >?, <=?, >=?). Handles CONTROL_FLOW_CHAIN with chain_type: "LESS_THAN_COALESCING_OPERATOR", "GREATER_THAN_COALESCING_OPERATOR", "LESS_EQUAL_COALESCING_OPERATOR", or "GREATER_EQUAL_COALESCING_OPERATOR".

EK9 Comparison Coalescing Operator Patterns:

• lhs <? rhs - Returns lesser value, gracefully handling null/unset
• lhs >? rhs - Returns greater value, gracefully handling null/unset
• lhs <=? rhs - Returns LHS if less-or-equal, else RHS, handling null/unset
• lhs >=? rhs - Returns LHS if greater-or-equal, else RHS, handling null/unset

Comparison Logic for lhs <? rhs:

1. If LHS is null → returns RHS
2. If LHS is not null BUT unset → returns RHS
3. If RHS is null → returns LHS
4. If RHS is not null BUT unset → returns LHS
5. If LHS < RHS → returns LHS (lesser value)
6. Otherwise → returns RHS

Key Differences from Other Coalescing Operators:

• Null coalescing (??) - 1 case (NULL check only)
• Elvis coalescing (:?) - 2 cases (NULL + IS_SET on LHS only)
• Comparison coalescing (<?, >?, <=?, >=?) - 5 cases (NULL + IS_SET on BOTH operands + comparison)

IR Structure (example for <? operator):

CONTROL_FLOW_CHAIN [chain_type: "LESS_THAN_COALESCING_OPERATOR"]
  condition_chain:
    [case 1: case_type: "NULL_CHECK"]
      condition_evaluation: [LOAD lhs, IS_NULL lhs]
      primitive_condition: lhs_is_null
      body_evaluation: [LOAD rhs]
      body_result: rhs
    [case 2: case_type: "EXPRESSION"]
      condition_evaluation: [CALL lhs._isSet(), CALL result._false()]
      condition_result: lhs_isSet (EK9 Boolean)
      primitive_condition: lhs_not_set (inverted)
      body_evaluation: [LOAD rhs]
      body_result: rhs
    [case 3: case_type: "NULL_CHECK"]
      condition_evaluation: [LOAD rhs, IS_NULL rhs]
      primitive_condition: rhs_is_null
      body_evaluation: []  // LHS already loaded
      body_result: lhs
    [case 4: case_type: "EXPRESSION"]
      condition_evaluation: [CALL rhs._isSet(), CALL result._false()]
      condition_result: rhs_isSet (EK9 Boolean)
      primitive_condition: rhs_not_set (inverted)
      body_evaluation: []  // LHS already loaded
      body_result: lhs
    [case 5: case_type: "EXPRESSION"]
      condition_evaluation: [CALL lhs._lt(rhs), CALL result._true()]
      condition_result: comparison (EK9 Boolean)
      primitive_condition: is_less_than
      body_evaluation: []  // LHS already loaded
      body_result: lhs
  default_body_evaluation: [LOAD rhs]
  default_result: rhs

Safety: NULL_CHECK cases always precede _isSet() calls to prevent accessing unallocated memory.

Stack Frame Invariant: All paths arrive at 'end' label with empty stack. Result is stored in local variable (overall_result).

Nested Class Summary

Nested classes/interfaces inherited from class AbstractAsmGenerator

AbstractAsmGenerator.LocalVariableInfo, AbstractAsmGenerator.MethodContext, AbstractAsmGenerator.ScopeInfo, AbstractAsmGenerator.TempVariableSource

Field Summary

Fields inherited from class AbstractControlFlowAsmGenerator

context

Fields inherited from class AbstractAsmGenerator

classWriter, constructTargetTuple, outputVisitor

Constructor Summary

Constructors

Constructor	Description
ComparisonCoalescingOperatorAsmGenerator(ConstructTargetTuple constructTargetTuple, OutputVisitor outputVisitor, org.objectweb.asm.ClassWriter classWriter, BytecodeGenerationContext context)

Method Summary

Modifier and Type	Method	Description
void	generate(ControlFlowChainInstr instr)	Generate bytecode for comparison coalescing operators (<?, >?, <=?, >=?).

Methods inherited from class AbstractControlFlowAsmGenerator

branchIfFalse, branchIfTrue, copyResultVariable, createControlFlowLabel, jumpTo, placeLabel, processBodyEvaluation, processConditionCase, processConditionCaseWithoutLabelPlacement, processConditionEvaluation, processInstructions

Methods inherited from class AbstractAsmGenerator

convertToJvmDescriptor, convertToJvmName, extractFieldName, generateBooleanLiteral, generateCharacterLiteral, generateDebugInfo, generateFloatLiteral, generateIntegerLiteral, generateLoadVariable, generateLocalVariableTable, generateMethodDescriptor, generateObjectLiteral, generateStackOperation, generateStoreVariable, generateStringLiteral, getCurrentMethodVisitor, getFieldDescriptor, getMethodContext, getOrCreateLabel, getOwnerClassName, getVariableIndex, isFieldAccess, isVariableAllocated, setCurrentMethodVisitor, setSharedMethodContext, trackTempVariableFromLiteral, trackTempVariableFromLoad

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

ComparisonCoalescingOperatorAsmGenerator

ComparisonCoalescingOperatorAsmGenerator(ConstructTargetTuple constructTargetTuple,
 OutputVisitor outputVisitor,
 org.objectweb.asm.ClassWriter classWriter,
 BytecodeGenerationContext context)

Method Details

generate

public void generate(ControlFlowChainInstr instr)

Generate bytecode for comparison coalescing operators (<?, >?, <=?, >=?).

Bytecode Pattern (example for <? ):

// Case 1: Check if LHS is null
ALOAD lhs_index
IFNONNULL lhs_not_null_label
// NULL case: load RHS
ALOAD rhs_index
ASTORE result_index
GOTO end_label

lhs_not_null_label:
// Case 2: Check if LHS is set
ALOAD lhs_index
INVOKEVIRTUAL _isSet()
INVOKEVIRTUAL _false()  // Inverted: if NOT set
ILOAD invertedPrimitive_index
IFEQ lhs_is_set_label
// UNSET case: load RHS
ALOAD rhs_index
ASTORE result_index
GOTO end_label

lhs_is_set_label:
// Case 3: Check if RHS is null
ALOAD rhs_index
IFNONNULL rhs_not_null_label
// NULL case: load LHS
ALOAD lhs_index
ASTORE result_index
GOTO end_label

rhs_not_null_label:
// Case 4: Check if RHS is set
ALOAD rhs_index
INVOKEVIRTUAL _isSet()
INVOKEVIRTUAL _false()  // Inverted: if NOT set
ILOAD invertedPrimitive_index
IFEQ rhs_is_set_label
// UNSET case: load LHS
ALOAD lhs_index
ASTORE result_index
GOTO end_label

rhs_is_set_label:
// Case 5: Perform comparison (LHS < RHS)
ALOAD lhs_index
ALOAD rhs_index
INVOKEVIRTUAL _lt(RHS_type)
INVOKEVIRTUAL _true()
ILOAD comparison_index
IFEQ comparison_false_label
// COMPARISON TRUE: load LHS
ALOAD lhs_index
ASTORE result_index
GOTO end_label

comparison_false_label:
// COMPARISON FALSE: load RHS (default case)
ALOAD rhs_index
ASTORE result_index

end_label:
// result now holds correct value

Stack Frame Invariant: Pre-condition: stack is empty Post-condition: stack is empty (result in local variable)

Parameters:

instr - CONTROL_FLOW_CHAIN instruction with comparison coalescing type