Module regs 

Register state: 15 general-purpose 64-bit registers + PC.

PVM2 is RV64E — a 16-register integer base (x0–x15) — so it has the full 15 GPRs (x1, x2, x5–x15, plus x3, x4) with x0 hardwired to zero, plus an instruction pointer. x3/x4 map to the two high slots (13, 14) so the 13 commonly-used registers keep slots 0..=12; the recompiler holds those 13 in host registers and spills x3/x4 to memory (see reg_is_spilled). Only x16–x31 (which do not exist in the E base) remain reserved.

Structs

Regs

Full register state: 15 GPRs + PC.

Enums

RegClass

Classification of a 5-bit RV register index in PVM2.

Constants

REG_COUNT

Number of general-purpose registers.

REG_SLOT_LUT

32-entry const-folded copy of reg_slot_or_ff for the recompiler’s codegen/gas hot path — a single load beats the range-match (the profiler showed the match at ~8.8% of compile). Generated from reg_class, so it cannot drift from the canonical classification.

Functions

reg_class

Classify a 5-bit RV register index (low 5 bits of x). See RegClass.

reg_is_reserved

True iff x is a reserved register (x16..x31 — they do not exist in the RV64E base) — as opposed to x0, which also lacks a slot but is valid. Drives the reserved-encoding (illegal) check in both engines.

reg_is_spilled

True iff x is a spilled register — x3 or x4, the two GPRs that map to the high slots (13, 14). They are real, fully-valid registers (the interpreter executes them as ordinary GPRs), but the x86-64 recompiler’s host register file is exhausted by the other 13 slots, so it holds x3/x4 in memory and materialises them per access. The recompiler uses this to route an x3/x4 instruction to its cold spill path; the gas model uses it to charge the memory-spill cost.

reg_slot_or_ff

PVM2 GPR slot (0..=14) for x, or 0xFF if x has no slot — x0 (hardwired zero) or a reserved register (x16..x31). The gas simulator reads 0xFF as “no dependency / no write”; both engines’ gas paths use this (the recompiler via the const-folded REG_SLOT_LUT) so gas agrees bit-for-bit. Note 0xFF conflates x0 with reserved — use reg_is_reserved when that distinction matters.