Summary

When a memory uses loadMemoryFromFileInline, running firtool with --repl-seq-mem appears to lose the memory initialization-file metadata in the companion output.

As a result, downstream external-memory generators can reconstruct the memory shape and ports, but cannot preserve the original $readmemh(...) initialization semantics.

Expected behavior

If a memory is annotated with loadMemoryFromFileInline, then after --repl-seq-mem the companion output should still preserve enough information to represent the memory-file initialization.

For example, the companion metadata could include an init_file field or another structured representation of the memory-file annotation.

Version

• Chisel: 6.6.0
• firtool: 1.73.0
• Scala: 2.13.15

Actual behavior

After --repl-seq-mem, the companion output only contains memory geometry / port information such as:

• name
• depth
• width
• ports
• mask_gran

but no initialization-file path.

This means a downstream tool can generate an external memory module, but cannot emit $readmemh(...) for a memory that originally used loadMemoryFromFileInline.

Minimal reproducer shape

In Chisel, the memory is created like this:

val rom = SyncReadMem(byteTableDepth, UInt(32.W))
loadMemoryFromFileInline(rom, romFile)

Then SystemVerilog is emitted with:

ChiselStage.emitSystemVerilogFile(
  new Top,
  firtoolOpts = Array(
    "--repl-seq-mem",
    "--repl-seq-mem-file=out.sv.conf"
  )
)

Observed companion output

The generated .sv.conf contains entries like:

name some_memory_ext depth 8192 width 32 ports read

No initialization-file field is present.

The generated SystemVerilog only contains an external-memory placeholder such as:

// external module some_memory_ext

so the original $readmemh(...) information is no longer available to downstream tools.

Functional impact

Without --repl-seq-mem, the memory initialization is preserved in the generated Verilog.

With --repl-seq-mem, the initialization-file information is not preserved in the companion output, so a downstream external-memory flow cannot reconstruct equivalent behavior.

Question

Is this an intended limitation of --repl-seq-mem, or should memory-file initialization metadata be preserved in the companion output?