Program 20: Branch-heavy loop

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Purpose

Provide frequent taken branches interleaved with two simple ALU updates.

This is one of the six workload fixtures. This page specifies its instructions and architectural result; pipeline cycles, stalls, and throughput are implementation-specific and are not established by this reference run.

Setup

Property	Value
Benchmark workload ID	program-20
Headless selection	--program 20
Visualizer scenario	rv32i-program20
Registered test	RV32ISingleCycleSystemTest/program-20
Instruction image	6 words, starting at 0x00000000; last word at 0x00000014
Initial state	PC = 0x00000000; all registers zero; neither halted nor trapped
Memories	Separate instruction and data memories, 256 KiB each; unlisted data bytes zero

Start address	Bytes, in increasing address order
None	—

The table lists the complete preloaded data image, not instruction bytes. No data image is required.

Register	Role established by the program
x1	Countdown from 16
x2	Accumulator counting iterations

The shared setup describes reset, loading, and the behavioral-core selection. These hand-written programs do not use the standard ABI stack.

Assembly

Every instruction word is shown, including words that a trap or branch may prevent from executing. Address and word comments identify the exact fixture image.

addi x1, x0, 16                # 0x00000000 | 0x01000093
addi x2, x0, 0                 # 0x00000004 | 0x00000113
loop:
addi x2, x2, 1                 # 0x00000008 | 0x00110113
addi x1, x1, -1                # 0x0000000C | 0xFFF08093
bne x1, x0, loop               # 0x00000010 | 0xFE009CE3
ebreak                         # 0x00000014 | 0x00100073

Execution

1. Initialize count 16 and accumulator zero.
2. Each iteration increments x2, decrements x1, and executes BNE back to the first update while the count is nonzero.
3. The branch is taken fifteen times and falls through on the sixteenth. The final values are x1=0 and x2=16.
4. EBREAK completes 2 + 16 × 3 + 1 = 51 attempts.

One branch per three loop instructions makes redirects frequent. The reference does not assign a pipeline flush penalty to them.

Expected result

These are the fixture's explicit final-state assertions. Unlisted registers are not implicitly zero; their values follow the assembly. The store table enumerates every written byte, including zero-valued writes.

Item	Expected value	Meaning
x1	0x00000000	Countdown from 16
x2	0x00000010	Accumulator counting iterations
PC	0x00000014	EBREAK address
Attempts	51	Checkpoints I0–I50
HALTED	1	Project halt
TRAPPED	0	No exception
TRAP_CAUSE	0	None, a project enum code

Start address	Bytes, in increasing address order
None	—

No data writes occur; the initial data image is unchanged. All data memory remains unchanged; there are no loads or stores.

Simulation and checkpoints

For a headless functional check, run build/rv32i_experiment --core single --program 20 --period 4000 --max-cycles 4096 --allocation-limit-mib 512. Select baseline or advanced for the same fixture on another core; add --fidelity reference for the structural-datapath reference profile. The explicit period is a scheduling choice, not a performance result. Use the campaign procedure for clock-certified measurements.

All 51 instruction attempts are included, with absolute simulator time and checkpoint number. The terminating EBREAK is included. The table is scrollable in both directions. Observation conventions distinguish these attempts from loaded word addresses and hardware cycles.

All 51 instruction-attempt checkpoints of RV32ISingleCycleSystemTest/program-20, with a behavioral core. Times are absolute simulator units, not milliseconds or an ISA latency.

Checkpoint	Time	Instruction / address	Expected architectural effects
I0	7080	ADDI @ 0x00000000	raw=0x01000093, pc_after=0x00000004, wb=x1=0x00000010, mem=None, flow=next
I1	11080	ADDI @ 0x00000004	raw=0x00000113, pc_after=0x00000008, wb=x2=0x00000000, mem=None, flow=next
I2	15080	ADDI @ 0x00000008	raw=0x00110113, pc_after=0x0000000c, wb=x2=0x00000001, mem=None, flow=next
I3	19080	ADDI @ 0x0000000c	raw=0xfff08093, pc_after=0x00000010, wb=x1=0x0000000f, mem=None, flow=next
I4	23080	BNE @ 0x00000010	raw=0xfe009ce3, pc_after=0x00000008, wb=None, mem=None, branch=BNE taken=true
I5	27080	ADDI @ 0x00000008	raw=0x00110113, pc_after=0x0000000c, wb=x2=0x00000002, mem=None, flow=next
I6	31080	ADDI @ 0x0000000c	raw=0xfff08093, pc_after=0x00000010, wb=x1=0x0000000e, mem=None, flow=next
I7	35080	BNE @ 0x00000010	raw=0xfe009ce3, pc_after=0x00000008, wb=None, mem=None, branch=BNE taken=true
I8	39080	ADDI @ 0x00000008	raw=0x00110113, pc_after=0x0000000c, wb=x2=0x00000003, mem=None, flow=next
I9	43080	ADDI @ 0x0000000c	raw=0xfff08093, pc_after=0x00000010, wb=x1=0x0000000d, mem=None, flow=next
I10	47080	BNE @ 0x00000010	raw=0xfe009ce3, pc_after=0x00000008, wb=None, mem=None, branch=BNE taken=true
I11	51080	ADDI @ 0x00000008	raw=0x00110113, pc_after=0x0000000c, wb=x2=0x00000004, mem=None, flow=next
I12	55080	ADDI @ 0x0000000c	raw=0xfff08093, pc_after=0x00000010, wb=x1=0x0000000c, mem=None, flow=next
I13	59080	BNE @ 0x00000010	raw=0xfe009ce3, pc_after=0x00000008, wb=None, mem=None, branch=BNE taken=true
I14	63080	ADDI @ 0x00000008	raw=0x00110113, pc_after=0x0000000c, wb=x2=0x00000005, mem=None, flow=next
I15	67080	ADDI @ 0x0000000c	raw=0xfff08093, pc_after=0x00000010, wb=x1=0x0000000b, mem=None, flow=next
I16	71080	BNE @ 0x00000010	raw=0xfe009ce3, pc_after=0x00000008, wb=None, mem=None, branch=BNE taken=true
I17	75080	ADDI @ 0x00000008	raw=0x00110113, pc_after=0x0000000c, wb=x2=0x00000006, mem=None, flow=next
I18	79080	ADDI @ 0x0000000c	raw=0xfff08093, pc_after=0x00000010, wb=x1=0x0000000a, mem=None, flow=next
I19	83080	BNE @ 0x00000010	raw=0xfe009ce3, pc_after=0x00000008, wb=None, mem=None, branch=BNE taken=true
I20	87080	ADDI @ 0x00000008	raw=0x00110113, pc_after=0x0000000c, wb=x2=0x00000007, mem=None, flow=next
I21	91080	ADDI @ 0x0000000c	raw=0xfff08093, pc_after=0x00000010, wb=x1=0x00000009, mem=None, flow=next
I22	95080	BNE @ 0x00000010	raw=0xfe009ce3, pc_after=0x00000008, wb=None, mem=None, branch=BNE taken=true
I23	99080	ADDI @ 0x00000008	raw=0x00110113, pc_after=0x0000000c, wb=x2=0x00000008, mem=None, flow=next
I24	103080	ADDI @ 0x0000000c	raw=0xfff08093, pc_after=0x00000010, wb=x1=0x00000008, mem=None, flow=next
I25	107080	BNE @ 0x00000010	raw=0xfe009ce3, pc_after=0x00000008, wb=None, mem=None, branch=BNE taken=true
I26	111080	ADDI @ 0x00000008	raw=0x00110113, pc_after=0x0000000c, wb=x2=0x00000009, mem=None, flow=next
I27	115080	ADDI @ 0x0000000c	raw=0xfff08093, pc_after=0x00000010, wb=x1=0x00000007, mem=None, flow=next
I28	119080	BNE @ 0x00000010	raw=0xfe009ce3, pc_after=0x00000008, wb=None, mem=None, branch=BNE taken=true
I29	123080	ADDI @ 0x00000008	raw=0x00110113, pc_after=0x0000000c, wb=x2=0x0000000a, mem=None, flow=next
I30	127080	ADDI @ 0x0000000c	raw=0xfff08093, pc_after=0x00000010, wb=x1=0x00000006, mem=None, flow=next
I31	131080	BNE @ 0x00000010	raw=0xfe009ce3, pc_after=0x00000008, wb=None, mem=None, branch=BNE taken=true
I32	135080	ADDI @ 0x00000008	raw=0x00110113, pc_after=0x0000000c, wb=x2=0x0000000b, mem=None, flow=next
I33	139080	ADDI @ 0x0000000c	raw=0xfff08093, pc_after=0x00000010, wb=x1=0x00000005, mem=None, flow=next
I34	143080	BNE @ 0x00000010	raw=0xfe009ce3, pc_after=0x00000008, wb=None, mem=None, branch=BNE taken=true
I35	147080	ADDI @ 0x00000008	raw=0x00110113, pc_after=0x0000000c, wb=x2=0x0000000c, mem=None, flow=next
I36	151080	ADDI @ 0x0000000c	raw=0xfff08093, pc_after=0x00000010, wb=x1=0x00000004, mem=None, flow=next
I37	155080	BNE @ 0x00000010	raw=0xfe009ce3, pc_after=0x00000008, wb=None, mem=None, branch=BNE taken=true
I38	159080	ADDI @ 0x00000008	raw=0x00110113, pc_after=0x0000000c, wb=x2=0x0000000d, mem=None, flow=next
I39	163080	ADDI @ 0x0000000c	raw=0xfff08093, pc_after=0x00000010, wb=x1=0x00000003, mem=None, flow=next
I40	167080	BNE @ 0x00000010	raw=0xfe009ce3, pc_after=0x00000008, wb=None, mem=None, branch=BNE taken=true
I41	171080	ADDI @ 0x00000008	raw=0x00110113, pc_after=0x0000000c, wb=x2=0x0000000e, mem=None, flow=next
I42	175080	ADDI @ 0x0000000c	raw=0xfff08093, pc_after=0x00000010, wb=x1=0x00000002, mem=None, flow=next
I43	179080	BNE @ 0x00000010	raw=0xfe009ce3, pc_after=0x00000008, wb=None, mem=None, branch=BNE taken=true
I44	183080	ADDI @ 0x00000008	raw=0x00110113, pc_after=0x0000000c, wb=x2=0x0000000f, mem=None, flow=next
I45	187080	ADDI @ 0x0000000c	raw=0xfff08093, pc_after=0x00000010, wb=x1=0x00000001, mem=None, flow=next
I46	191080	BNE @ 0x00000010	raw=0xfe009ce3, pc_after=0x00000008, wb=None, mem=None, branch=BNE taken=true
I47	195080	ADDI @ 0x00000008	raw=0x00110113, pc_after=0x0000000c, wb=x2=0x00000010, mem=None, flow=next
I48	199080	ADDI @ 0x0000000c	raw=0xfff08093, pc_after=0x00000010, wb=x1=0x00000000, mem=None, flow=next
I49	203080	BNE @ 0x00000010	raw=0xfe009ce3, pc_after=0x00000014, wb=None, mem=None, branch=BNE taken=false
I50	207080	EBREAK @ 0x00000014	raw=0x00100073, pc_after=0x00000014, wb=None, mem=None, flow=next, halted=true

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