All 3 compilers FAIL: l1a/l1b miss returnAddress push/type; L2 explicitly unsupported

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Spec Compliance Report for jsr_w

Compiler	Status	Issues
l1a	❌ FAIL	Missing operand stack push of returnAddress; no returnAddress type support; ret/jsr asymmetry not modeled
l1b	❌ FAIL	Missing operand stack push of returnAddress; no returnAddress type support; ret/jsr asymmetry not modeled
l2	❌ FAIL	Explicitly unsupported in L2ByteCodeSupportChecker and IRGenerator

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Details

l1a Implementation

• Status: ❌ FAIL
• Files: core/src/core/org/jnode/vm/x86/compiler/l1a/X86BytecodeVisitor.java:2960-2962, core/src/core/org/jnode/vm/x86/compiler/l1a/X86BytecodeVisitor.java:3886-3892
• Issues:
  1. Missing operand stack push (line 2960-2962): visit_jsr only emits os.writeCALL(helper.getInstrLabel(address)). Per JVM spec, the address of the next instruction (return address) must be pushed onto the operand stack as a returnAddress type value. The x86 CALL pushes to hardware stack, not JVM operand stack.
  2. No returnAddress type support: The JVM returnAddress type is not represented in JvmType, Item hierarchy, or type system. No ReturnAddressItem class exists.
  3. ret/jsr asymmetry not modeled (line 3886-3892): visit_ret does os.writeJMP(helper.BP, ebpOfs) — jumps to address stored in local variable — but jsr never pushed that address to the operand stack for subsequent astore by the subroutine.
  4. BytecodeParser correct (BytecodeParser.java:890-891): Properly decodes 32-bit signed offset via gets4() and computes absolute target.

l1b Implementation

• Status: ❌ FAIL
• Files: core/src/core/org/jnode/vm/x86/compiler/l1b/X86BytecodeVisitor.java:3687-3692, core/src/core/org/jnode/vm/x86/compiler/l1b/X86BytecodeVisitor.java:4830-4839
• Issues: Identical to l1a — same writeCALL implementation, same missing operand stack push, same missing returnAddress type, same ret/jsr asymmetry.

l2 Implementation

• Status: ❌ FAIL
• Files:
  • core/src/core/org/jnode/vm/x86/compiler/l2/L2ByteCodeSupportChecker.java:163-165
  • core/src/core/org/jnode/vm/compiler/ir/IRGenerator.java:1321-1323
  • core/src/core/org/jnode/vm/compiler/ir/IRBasicBlockFinder.java:216-220
• Issues:
  1. Explicitly unsupported: Both L2ByteCodeSupportChecker.visit_jsr and IRGenerator.visit_jsr throw UnsupportedOperationException.
  2. Basic block analysis incomplete: IRBasicBlockFinder.visit_jsr doesn't add branch target or fall-through as successors.
  3. No returnAddress type in IR: The IR Operand type system has no RETURN_ADDRESS category.

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Key JVM Spec Requirements (from https://docs.oracle.com/javase/specs/jvms/se6/html/Instructions2.doc7.html)

• Operand Stack: ... → ..., address (pushes returnAddress type)
• Branch Offset: Signed 32-bit, computed from 4 bytes
• Target: Must be opcode within same method
• Asymmetry: jsr_w pushes to operand stack; ret retrieves from local variable

Closes #330

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