Add ASSIGN_NOPUSH to eliminate redundant assignment pushes

[bertysentry]

Summary

• Add a dedicated ASSIGN_NOPUSH opcode for scalar assignments whose result is immediately discarded
• Update tuple peephole optimization to rewrite ASSIGN + POP into ASSIGN_NOPUSH
• Teach the AVM to handle both assignment opcodes and skip the stack push for the nopush form
• Add optimizer coverage for statement assignments and assignment expressions

Testing

• mvn formatter:format test -Dtest=AwkTupleOptimizationTest
• mvn test
• mvn verify

[Copilot]

Pull request overview

This PR introduces a new scalar-assignment opcode (ASSIGN_NOPUSH) to avoid redundant operand-stack pushes when an assignment’s result is immediately discarded, and updates the peephole optimizer, opcode definitions, AVM execution, and optimizer tests accordingly.

Changes:

• Add ASSIGN_NOPUSH opcode and document distinct stack semantics vs ASSIGN.
• Extend the peephole optimizer to rewrite ASSIGN followed by POP into ASSIGN_NOPUSH.
• Update the AVM assignment execution path to optionally skip pushing the assigned value; add tests asserting the optimizer behavior for statement vs expression assignments.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/test/java/io/jawk/AwkTupleOptimizationTest.java	Adds optimizer tests and opcode-scanning helpers to validate folding behavior.
src/main/java/io/jawk/intermediate/Opcode.java	Introduces ASSIGN_NOPUSH and clarifies ASSIGN stack behavior in docs.
src/main/java/io/jawk/intermediate/AwkTuples.java	Adds peephole rewrite for ASSIGN + POP -> ASSIGN_NOPUSH and tuple construction helper.
src/main/java/io/jawk/backend/AVM.java	Executes ASSIGN_NOPUSH by assigning without re-pushing; removes redundant push/pop in a couple of internal assignment sites.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.