bpf: Add loop test case with 32 bit reg comparison against 0

Add a loop test with 32 bit register against 0 immediate:

# ./test_verifier 631
#631/p taken loop with back jump to 1st insn, 2 OK

Disassembly:

[...]
1b: test %edi,%edi
1d: jne 0x0000000000000014
[...]

Pretty much similar to prior "taken loop with back jump to 1st
insn" test case just as jmp32 variant.

Signed-off-by: Daniel Borkmann <[e-mail]>
Signed-off-by: Alexei Starovoitov <[e-mail]>
Acked-by: Song Liu <[e-mail]>

tools/testing/selftests/bpf/verifier/loops1.c

···
 	.prog_type = BPF_PROG_TYPE_XDP,
 	.retval = 55,
 },
+{
+	"taken loop with back jump to 1st insn, 2",
+	.insns = {
+	BPF_MOV64_IMM(BPF_REG_1, 10),
+	BPF_MOV64_IMM(BPF_REG_2, 0),
+	BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 1, 0, 1),
+	BPF_EXIT_INSN(),
+	BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_1),
+	BPF_ALU64_IMM(BPF_SUB, BPF_REG_1, 1),
+	BPF_JMP32_IMM(BPF_JNE, BPF_REG_1, 0, -3),
+	BPF_MOV64_REG(BPF_REG_0, BPF_REG_2),
+	BPF_EXIT_INSN(),
+	},
+	.result = ACCEPT,
+	.prog_type = BPF_PROG_TYPE_XDP,
+	.retval = 55,
+},