Module generate 

RV64E-subset program generator.

Two modes, sharing one boundary-biased operand pool:

• enumerate_boundary — deterministic, near-exhaustive over each op × boundary-operand combination. This is what guarantees the high-value corners appear (e.g. div x?, INT_MIN, -1).
• Gen::random_program — random instruction sequences for cross-op / cross-state breadth, seeded for reproducibility.

Every generated program is total by construction: register-only, straight-line, over x0–x15 minus the spilled (x3/x4) and x6/x7 (left at 0 so their signature slots are deterministic), ending in encode::signature_epilogue. So it always halts cleanly on a conformant engine — and on the oracle — with a defined register signature. (The div corners are included: RISC-V defines INT_MIN/-1 as a value, so the oracle and interpreter produce one; only a buggy recompiler diverges.)

v1 emits register-only ops (no loads/stores/branches — those want a memory window / control flow and come later); this already covers the value-domain edge cases that matter most (div overflow, shift masking, W-op sign-extension, mulhsu, Zbb corners).

Structs

Gen

Random program generator.

XorShift64

Small, fast, deterministic PRNG (xorshift64* — state never zero).

Constants

IMM20S

Boundary 20-bit upper immediates (for lui/auipc).

IMMS

Boundary 12-bit-signed immediates (for I-type ALU).

OPERANDS

Boundary-biased operand pool — the values bugs hide at.

SHAMTS

Boundary shift amounts — includes the out-of-range 64/65 that exercise the & 63 / & 31 masking both engines (must) perform.

Functions

enumerate_boundary

Deterministic boundary enumeration. For each register-only op, emit one program per relevant boundary-operand combination, seeding source registers x8/x9 and writing the result to x10. Guarantees the corner cases appear.