l1a/l1b: 32-bit OK, 64-bit broken. l2: FAIL.

[opencode-agent]

Spec compliance report

Compiler	Status	Issues
l1a	⚠️ PARTIAL	32-bit: PASS. 64-bit: Missing Long.MIN_VALUE/-1 special case handling; 64-bit assembly missing int_div handler for #DE
l1b	⚠️ PARTIAL	Same as l1a
l2	❌ FAIL	32-bit: Throws IllegalArgumentException at codegen. 64-bit: Not implemented. L2ByteCodeSupportChecker incorrectly reports support

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Details

l1a Implementation

• Status: ⚠️ PARTIAL
• Files:
  • core/src/core/org/jnode/vm/x86/compiler/l1a/X86BytecodeVisitor.java:3184-3227 (visit_ldiv)
  • core/src/core/org/jnode/vm/MathSupport.java:41-94 (ldiv implementation for 32-bit)
• 32-bit mode (line 3188-3196): Delegates to MathSupport.ldiv() via invokeJavaMethod(context.getLdivMethod()). MathSupport.ldiv() correctly implements JVM spec:
  • Division by zero → throws ArithmeticException (line 70)
  • Long.MIN_VALUE / -1 → returns Long.MIN_VALUE (lines 42-53, special case handling)
  • Normal division with truncation toward zero
• 64-bit mode (lines 3197-3226): Uses native x86 IDIV:
  • Pops v2 (divisor), v1 (dividend) — correct stack order
  • Loads v1 into RAX, sign-extends to RDX:RAX via CDQ
  • Executes IDIV (RDX:RAX / v2.reg), quotient in RAX
  • ISSUE 1 (line 3215-3218): Long.MIN_VALUE / -1 causes x86 #DE (divide error) because quotient overflows 64 bits. JVM spec requires returning Long.MIN_VALUE with NO exception. Current implementation will trigger #DE.
  • ISSUE 2: 64-bit assembly (core/src/native/x86/ints64.asm) lacks int_div handler for vector 0 (#DE). The handler exists only in ints32.asm:240-244. Without it, division by zero in 64-bit mode will not be converted to ArithmeticException.

l1b Implementation

• Status: ⚠️ PARTIAL
• Files:
  • core/src/core/org/jnode/vm/x86/compiler/l1b/X86BytecodeVisitor.java:3976-4029 (visit_ldiv)
  • core/src/core/org/jnode/vm/MathSupport.java:41-94 (shared 32-bit implementation)
• 32-bit mode (lines 3981-3998): Identical to l1a — delegates to MathSupport.ldiv(). PASS
• 64-bit mode (lines 3999-4028): Identical to l1a — uses native IDIV. Same two issues as l1a 64-bit

l2 Implementation

• Status: ❌ FAIL
• Files:
  • core/src/core/org/jnode/vm/x86/compiler/l2/GenericX86CodeGenerator.java:3630-3637 (32-bit stack-based generateBinaryOP)
  • core/src/core/org/jnode/vm/x86/compiler/l2/L2ByteCodeSupportChecker.java (no override for visit_ldiv)
• 32-bit mode: In generateBinaryOP(int disp1, int disp2, BinaryOperation operation, int disp3) at line 3631, LDIV falls through to throw new IllegalArgumentException("Unknown operation: " + operation). Code generation fails at compile time.
• 64-bit mode: No implementation. Several // if (os.isCode64()) comments (lines 4022, 4066, 4113, 4612, 5278, 5453) indicate incomplete 64-bit support.
• L2ByteCodeSupportChecker: Does not override visit_ldiv(), inherits no-op from BytecodeVisitorSupport:923. This causes L2 to incorrectly believe ldiv is supported, leading to runtime codegen failures.

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JVM Spec References

• ldiv spec: https://docs.oracle.com/javase/specs/jvms/se6/html/Instructions2.doc8.html
• Operand stack effect: ..., value1, value2 → ..., result
• Division semantics: Truncates toward zero
• Special case: Long.MIN_VALUE / -1 → Long.MIN_VALUE (overflow, no exception)
• Runtime exception: ArithmeticException if divisor == 0

---

JNode File References

• L1A 32-bit: core/src/core/org/jnode/vm/x86/compiler/l1a/X86BytecodeVisitor.java:3188-3196
• L1A 64-bit: core/src/core/org/jnode/vm/x86/compiler/l1a/X86BytecodeVisitor.java:3197-3226
• L1B 32-bit: core/src/core/org/jnode/vm/x86/compiler/l1b/X86BytecodeVisitor.java:3981-3998
• L1B 64-bit: core/src/core/org/jnode/vm/x86/compiler/l1b/X86BytecodeVisitor.java:3999-4028
• MathSupport (32-bit impl): core/src/core/org/jnode/vm/MathSupport.java:41-94
• L2 32-bit codegen failure: core/src/core/org/jnode/vm/x86/compiler/l2/GenericX86CodeGenerator.java:3630-3637
• L2 support checker: core/src/core/org/jnode/vm/x86/compiler/l2/L2ByteCodeSupportChecker.java (no visit_ldiv override)
• 32-bit #DE handler: core/src/native/x86/ints32.asm:240-244
• 64-bit #DE handler: MISSING from core/src/native/x86/ints64.asm

Closes #341

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