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| author | Eduard Zingerman <eddyz87@gmail.com> | 2026-10-26 16:38:30 -0700 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2026-10-27 16:26:21 +0000 |
| commit | a0137c789774bdc2eff9b1b4525741ed118eeba0 (patch) | |
| tree | f49c192f1cc8f755e4a096efbbb56dc3fc58efc4 /tools/testing | |
| parent | 344c14e8b3d45e3c643cec1ba6acd3e4691dfe66 (diff) | |
selftests/bpf: 32-bit copy of the counter compared at the latch
When building SCEV expressions for the loop:
w7 = w1; r7 = (zext32 r1)
w1 = w7; r1 = (zext32 (zext32 r1))
w1 += 2; r1 = (zext32 (+ (zext32 (zext32 r1)) 2))
Computed SCEV expression for r1:
(zext32 (linear r1 2))
Substituting this into r7's expression at the latch:
(zext32 (zext32 (linear r1 2)))
Without (zext32 (zext32 X)) -> (zext32 X) simplification rule
the latch would not be recognized as linear and header_count
won't be computed.
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://patch.msgid.link/20261026-scev-simpler-clamp-v2-10-f373aec9825f@gmail.com
Diffstat (limited to 'tools/testing')
| -rw-r--r-- | tools/testing/selftests/bpf/progs/verifier_scev.c | 27 |
1 files changed, 27 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/progs/verifier_scev.c b/tools/testing/selftests/bpf/progs/verifier_scev.c index 39603c8bf083..37434efd1490 100644 --- a/tools/testing/selftests/bpf/progs/verifier_scev.c +++ b/tools/testing/selftests/bpf/progs/verifier_scev.c @@ -3710,4 +3710,31 @@ __naked void dominating_exit_bounds_count(void) " ::: __clobber_all); } +/* + * The counter is copied to a callee-saved register for the call and the copy is compared. + */ +SEC("xdp") +__success +__log_level(2) +__flag(BPF_F_TEST_STATE_FREQ) +__msg(" scev at latch 5:") +__msg(" r7=(zext32 r1) / (zext32 (linear r1 2))") +__msg("loop header at 1, header_count is 100 ") +__msg("loop header at 1, widening r1 to 0..198 step 2") +__naked void post_cond_jlt32_copy(void) +{ + asm volatile (" \ + w1 = 0; \ +1: w7 = w1; \ + call %[bpf_get_prandom_u32]; \ + w1 = w7; \ + w1 += 2; \ + if w7 < 198 goto 1b; \ + r0 = 0; \ + exit; \ +" : + : __imm(bpf_get_prandom_u32) + : __clobber_all); +} + char _license[] SEC("license") = "GPL"; |