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 (:?) - 1 case (LHS absent or not set, via the null-safe ?)
• Comparison coalescing (<?, >?, <=?, >=?) - 3 cases (each operand absent or not set, then the comparison)

IR Structure (example for <? operator). Each operand is generated ONCE: both are evaluated before any case (every path evaluates both, exactly once); "absent or not set" is the null-safe ? - a nested QUESTION_OPERATOR chain, IS_NULL before _isSet() - inverted. Generating the RHS per case, as this once did, made a nested chain grow as 3^n.

CONTROL_FLOW_CHAIN [chain_type: "LESS_THAN_COALESCING_OPERATOR"]
  condition_chain:
    [case 1: case_type: "EXPRESSION"]
      condition_evaluation: [LOAD lhs, lhs_set = QUESTION_OPERATOR(lhs), LOAD rhs, CALL lhs_set._false()]
      condition_result: lhs_set (EK9 Boolean)
      primitive_condition: lhs_not_set
      body_evaluation: [RETAIN rhs]
      body_result: rhs
    [case 2: case_type: "EXPRESSION"]
      condition_evaluation: [rhs_set = QUESTION_OPERATOR(rhs), CALL rhs_set._false()]
      condition_result: rhs_set (EK9 Boolean)
      primitive_condition: rhs_not_set
      body_evaluation: [RETAIN lhs]
      body_result: lhs
    [case 3: case_type: "EXPRESSION"]
      condition_evaluation: [CALL lhs._cmp(rhs), CALL cmp._lt(0), CALL result._true()]
      condition_result: comparison (EK9 Boolean)
      primitive_condition: is_less_than
      body_evaluation: [RETAIN lhs]
      body_result: lhs
  default_body_evaluation: [RETAIN rhs]
  default_result: rhs

Safety: the null-safe ? never calls _isSet() on an absent operand.

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

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, generateCoalescingPattern, jumpTo, placeLabel, processBodyEvaluation, processConditionCase, processConditionCaseWithoutLabelPlacement, processConditionEvaluation, processInstructions, processSequentialCaseChain

Methods inherited from class AbstractAsmGenerator

convertToJvmDescriptor, convertToJvmName, extractFieldName, generateBooleanLiteral, generateCharacterLiteral, generateDebugInfo, generateFloatLiteral, generateIntegerLiteral, generateLoadVariable, generateLocalVariableTable, generateMethodDescriptor, generateObjectLiteral, generateStackOperation, generateStoreVariable, generateStoreVariableAsInt, generateStringLiteral, getCurrentMethodVisitor, getFieldDescriptor, getMethodContext, getOrCreateLabel, getOwnerClassName, getVariableIndex, isFieldAccess, isVariableAllocated, isVariableFieldAccess, setCurrentMethodVisitor, setSharedMethodContext, toJvmFieldName, 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 (<?, >?, <=?, >=?).

Uses the common coalescing pattern from AbstractControlFlowAsmGenerator with an operator-specific label prefix.

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