compare-asm

name	compare-asm
description	Side-by-side target vs base assembly comparison with cluster boundaries and mismatch annotations. Shows aligned instructions with match markers, register swap details, and offset deltas. Use when diagnosing the last few percent of a function.
argument-hint	<symbol_name>
allowed-tools	Bash(python3 scripts/analysis/diff_inspect.py *), Read, Grep, Glob

Compare ASM Skill

Side-by-side target vs base assembly comparison with annotations.

Arguments

$ARGUMENTS - The function symbol name (mangled or demangled).

Steps

1. Run the comparison:

   python3 scripts/analysis/diff_inspect.py --symbol "$ARGUMENTS" --compare-asm --project-dir .
   

2. Read the output:

   • Match markers: = equal, ~ diff_arg (same opcode, different args), ! diff_op, + insert (target only), - delete (base only), X replace
   • Cluster boundaries mark contiguous insert/delete regions
   • [reg:rN->rM] annotations show register swap details
   • [off:+N] annotations show offset/immediate deltas
   • Consecutive equal instructions are collapsed (first 2 + last 2 shown)

3. Diagnosis summary at the end shows:

   • Mismatch type counts
   • Register swap pairs with frequency
   • Dominant offset delta

When to Use

• Working on a function's "last 10%" and need to see exactly where mismatches are
• Want to correlate register swaps with specific instruction sequences
• Need to understand the structure of insert/delete clusters
• Comparing the effect of a source change on assembly output

Output Size

• Equal instruction runs of 5+ are collapsed to save space
• Output is capped at 150 instruction rows for large functions
• Focus is on mismatch regions with context

Tips

• Combine with /rb2-locals to map registers to variable names
• Use --offsets mode separately for detailed offset histogram
• Use --regswaps mode for comprehensive register pair analysis