Compatibility graph

Every node is a published RISC-V extension. Every edge is an encoding relation the registry detected between two extensions —FATAL conflicts (full encoding tuple matches with different mnemonics),WARNING conflicts (remappable), designedSHARED overlaps (same instruction by spec),SHARED MAJOR OPCODE (informational; both live under the same 7-bit major opcode), and overlappingCUSTOM opcode spaces.

What “shared major opcode” means here

Many ratified extensions live under the same 7-bit major opcode by design — every RVV vector instruction sits at OP-V 0x57, atomics at AMO 0x2F, immediate ops at OP-IMM 0x13. Sharing the major opcode is not a conflict by itself. A real conflict requires overlapping full decode mask/match patterns, including any fixed register/immediate field constraints (the kind of reserved carve-outs that distinguish, say, two RVV instructions sharing funct3 + funct6). Such edges are now classified as SHARED_MAJOR_OPCODE and rendered in blue. FATAL in red is reserved for full-mask matches with different mnemonics — none on the graph today.

The current detector still works at the funct3/funct7/funct12 level; adding funct6 + register/immediate mask resolution is the next iteration, and will refine some of today's WARNINGs into either real conflicts or shared dispatch space.

102

Extensions

117

Edges

FATAL conflicts

Designed overlaps

100%

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Reading the graph

Nodes = published extensions. Color = Readiness Level (RL5 green → RL1 stone). Drag to reposition. Click to open the package page.
Edges = collisions detected by the registry. Hover for the encoding detail.
Cyan edges (SHARED) are designed overlaps, not real conflicts — e.g. Zbkb's rol and Zbb's rol are the same instruction by spec.
Scroll to zoom · drag the canvas to pan. Use “Reset view” to recenter.
“Hide isolated nodes” drops extensions with no visible edge from the canvas (otherwise they drift around as untethered points).