RISC-V Design · All levels
Branch Handling, Pipeline Flush, and Redirect Timing: Theory Deep Dive
Theory Deep Dive for Branch Handling, Pipeline Flush, and Redirect Timing.
Theory deep dive
Theory Deep Dive for Branch Handling, Pipeline Flush, and Redirect Timing is anchored on Branch mispredict penalty in cycles, wrong-path retire count (target zero), and redirect latency from resolve to fetch restart.. Convert observations into mechanism-backed decisions with explicit ownership.
Theory matters when it predicts engineering outcomes. Tie abstract ISA and microarchitecture concepts to measurable behavior in trace and counter data.
Pipeline model
diagram
RISC-V PIPELINE DIAGRAM - Branch Handling, Pipeline Flush, and Redirect Timing
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 predictablePrivilege model
diagram
PRIVILEGE MODE STACK - Branch Handling, Pipeline Flush, and Redirect Timing
+------------------------------+
| Machine mode (M) |
| firmware, PMP, trap root |
+---------------+--------------+
|
delegated traps
v
+------------------------------+
| Supervisor mode (S) |
| kernel, page tables, drivers |
+---------------+--------------+
|
ecall / syscall
v
+------------------------------+
| User mode (U) |
| applications, libraries |
+------------------------------+
Key rule: each upward transition records cause + PC in trap CSRs.