diff mbox

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

Message ID 1386107477-24165-12-git-send-email-peter.maydell@linaro.org
State Superseded
Headers show

Commit Message

Peter Maydell Dec. 3, 2013, 9:51 p.m. UTC 
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 |   30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

Comments

Richard Henderson Dec. 4, 2013, 12:07 a.m. UTC | #1 
On 12/04/2013 10:51 AM, Peter Maydell wrote:
> +    label_nomatch = gen_new_label();
> +    if (op) { /* TBNZ */
> +        tcg_gen_brcondi_i64(TCG_COND_EQ, tcg_cmp, 0, label_nomatch);
> +    } else { /* TBZ */
> +        tcg_gen_brcondi_i64(TCG_COND_NE, tcg_cmp, 0, label_nomatch);
> +    }
> +    tcg_temp_free_i64(tcg_cmp);
> +    gen_goto_tb(s, 0, addr);
> +    gen_set_label(label_nomatch);
> +    gen_goto_tb(s, 1, s->pc);

Similar to B.cond, I think it would be clearer to write positive tests than
negative tests.  Therefore TBNZ -> NE; TBZ -> EQ, and swap the two goto_tb.

Further, you can avoid some repetition of the brcondi with (?:).

Otherwise,

Reviewed-by: Richard Henderson <rth@twiddle.net>


r~
Peter Maydell Dec. 4, 2013, 12:22 a.m. UTC | #2 
On 4 December 2013 00:07, Richard Henderson <rth@twiddle.net> wrote:
> On 12/04/2013 10:51 AM, Peter Maydell wrote:
>> +    label_nomatch = gen_new_label();
>> +    if (op) { /* TBNZ */
>> +        tcg_gen_brcondi_i64(TCG_COND_EQ, tcg_cmp, 0, label_nomatch);
>> +    } else { /* TBZ */
>> +        tcg_gen_brcondi_i64(TCG_COND_NE, tcg_cmp, 0, label_nomatch);
>> +    }
>> +    tcg_temp_free_i64(tcg_cmp);
>> +    gen_goto_tb(s, 0, addr);
>> +    gen_set_label(label_nomatch);
>> +    gen_goto_tb(s, 1, s->pc);
>
> Similar to B.cond, I think it would be clearer to write positive tests than
> negative tests.  Therefore TBNZ -> NE; TBZ -> EQ, and swap the two goto_tb.
>
> Further, you can avoid some repetition of the brcondi with (?:).

OK, will fix.

thanks
-- PMM
diff mbox

Patch

diff --git a/target-arm/translate-a64.c b/target-arm/translate-a64.c
index 3c0748d..bcb59db 100644
--- a/target-arm/translate-a64.c
+++ b/target-arm/translate-a64.c
@@ -215,10 +215,36 @@  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_nomatch;
+    TCGv_i64 tcg_cmp;
+
+    bit_pos = (extract32(insn, 31, 1) << 5) | extract32(insn, 19, 5);
+    op = extract32(insn, 24, 1);
+    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_nomatch = gen_new_label();
+    if (op) { /* TBNZ */
+        tcg_gen_brcondi_i64(TCG_COND_EQ, tcg_cmp, 0, label_nomatch);
+    } else { /* TBZ */
+        tcg_gen_brcondi_i64(TCG_COND_NE, tcg_cmp, 0, label_nomatch);
+    }
+    tcg_temp_free_i64(tcg_cmp);
+    gen_goto_tb(s, 0, addr);
+    gen_set_label(label_nomatch);
+    gen_goto_tb(s, 1, s->pc);
 }
 
 /* C3.2.2 / C5.6.19 Conditional branch (immediate)