[Qemu-devel] [PATCH v2 11/12] target-arm: A64: add support for 'test and branch' imm

[Peter Maydell <peter.maydell@linaro.org>]

From: Alexander Graf <agraf@suse.de>

This patch adds emulation for the test and branch insns,
TBZ and TBNZ.

Signed-off-by: Alexander Graf <agraf@suse.de>
[claudio:
  adapted for new decoder
  always compare with 0
  remove a TCG temporary
]
Signed-off-by: Claudio Fontana <claudio.fontana@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target-arm/translate-a64.c |   27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/target-arm/translate-a64.c b/target-arm/translate-a64.c
index afad874..b79672b 100644
--- a/target-arm/translate-a64.c
+++ b/target-arm/translate-a64.c
@@ -215,10 +215,33 @@ static void disas_comp_b_imm(DisasContext *s, uint32_t insn)
     unsupported_encoding(s, insn);
 }
 
-/* Test & branch (immediate) */
+/* C3.2.5 Test & branch (immediate)
+ *   31  30         25  24  23   19 18          5 4    0
+ * +----+-------------+----+-------+-------------+------+
+ * | b5 | 0 1 1 0 1 1 | op |  b40  |    imm14    |  Rt  |
+ * +----+-------------+----+-------+-------------+------+
+ */
 static void disas_test_b_imm(DisasContext *s, uint32_t insn)
 {
-    unsupported_encoding(s, insn);
+    unsigned int bit_pos, op, rt;
+    uint64_t addr;
+    int label_match;
+    TCGv_i64 tcg_cmp;
+
+    bit_pos = (extract32(insn, 31, 1) << 5) | extract32(insn, 19, 5);
+    op = extract32(insn, 24, 1); /* 0: TBZ; 1: TBNZ */
+    addr = s->pc + sextract32(insn, 5, 14) * 4 - 4;
+    rt = extract32(insn, 0, 5);
+
+    tcg_cmp = tcg_temp_new_i64();
+    tcg_gen_andi_i64(tcg_cmp, cpu_reg(s, rt), (1ULL << bit_pos));
+    label_match = gen_new_label();
+    tcg_gen_brcondi_i64(op ? TCG_COND_NE : TCG_COND_EQ,
+                        tcg_cmp, 0, label_match);
+    tcg_temp_free_i64(tcg_cmp);
+    gen_goto_tb(s, 0, s->pc);
+    gen_set_label(label_match);
+    gen_goto_tb(s, 1, addr);
 }
 
 /* C3.2.2 / C5.6.19 Conditional branch (immediate)
-- 
1.7.9.5