RISC-V Design · All levels

Formal Pipeline Checks: Mechanism

Mechanism for Formal Pipeline Checks.

Mechanism to understand

Mechanism for Formal Pipeline Checks is anchored on Proof closure on pipeline safety/liveness properties with bounded-depth convergence and vacuity review.. Convert observations into mechanism-backed decisions with explicit ownership.

Formal pipeline checks encode invariants such as precise exception behavior, hazard handling correctness, no-commit-on-kill guarantees, and forward progress under legal assumptions. These properties expose corner-state bugs in control logic, bypass paths, and flush interactions that simulation may miss due to insufficient interleaving coverage. Successful deployment partitions checks by stage and protocol interface, constrains environments transparently, and tracks counterexample quality so proofs represent real architecture guarantees rather than over-constrained models.

Name first failing path and trigger condition.
Prove path loss with one measurable artifact.
Assign owner who can deliver smallest reversible fix.

Pipeline mechanism sketch

diagram

RISC-V PIPELINE DIAGRAM - Formal Pipeline Checks

PC -> IF -> ID -> EX -> MEM -> WB
      |     |      |      |      |
  i-cache decode  ALU/BR  LSU    regfile write
              \   |
               +-> branch resolve + redirect

Hot paths:
  - branch + load-use dependencies in ID/EX
  - memory latency stretching MEM stage
  - writeback arbitration for integer/vector units

Focus: keep control hazards predictable

Decode intent map

diagram

DECODE CONTROL MAP - Formal Pipeline Checks

opcode/funct3/funct7      controls asserted
-----------------------   ---------------------------------------
LUI / AUIPC               rd_write, imm_select(U), alu_add_pc
JAL / JALR                rd_write, pc_redirect, link_write
BRANCH                    cmp_enable, branch_type, pc_redirect
LOAD                      mem_read, rd_write, wb_sel(memory)
STORE                     mem_write, store_size, addr_calc
OP-IMM                    alu_enable, imm_select(I), rd_write
OP                        alu_enable, src2_reg, rd_write
SYSTEM / CSR              csr_readwrite, trap_check, privilege_gate
VECTOR (V extension)      vdecode, lane_mask, vtype_update

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