[Qemu-devel] [PULL 04/24] target-arm: Introduce DisasCompare

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

From: Richard Henderson <rth@twiddle.net>

Split arm_gen_test_cc into 3 functions, so that it can be reused
for non-branch TCG comparisons.

Signed-off-by: Richard Henderson <rth@twiddle.net>
Message-id: 1441909103-24666-3-git-send-email-rth@twiddle.net
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target-arm/translate.c | 115 +++++++++++++++++++++++++++++--------------------
 target-arm/translate.h |   9 ++++
 2 files changed, 78 insertions(+), 46 deletions(-)

diff --git a/target-arm/translate.c b/target-arm/translate.c
index f1b7c16..7d2e984 100644
--- a/target-arm/translate.c
+++ b/target-arm/translate.c
@@ -738,81 +738,104 @@ static void gen_thumb2_parallel_addsub(int op1, int op2, TCGv_i32 a, TCGv_i32 b)
 #undef PAS_OP
 
 /*
- * generate a conditional branch based on ARM condition code cc.
+ * Generate a conditional based on ARM condition code cc.
  * This is common between ARM and Aarch64 targets.
  */
-void arm_gen_test_cc(int cc, TCGLabel *label)
+void arm_test_cc(DisasCompare *cmp, int cc)
 {
-    TCGv_i32 tmp;
-    TCGLabel *inv;
+    TCGv_i32 value;
+    TCGCond cond;
+    bool global = true;
 
     switch (cc) {
     case 0: /* eq: Z */
-        tcg_gen_brcondi_i32(TCG_COND_EQ, cpu_ZF, 0, label);
-        break;
     case 1: /* ne: !Z */
-        tcg_gen_brcondi_i32(TCG_COND_NE, cpu_ZF, 0, label);
+        cond = TCG_COND_EQ;
+        value = cpu_ZF;
         break;
+
     case 2: /* cs: C */
-        tcg_gen_brcondi_i32(TCG_COND_NE, cpu_CF, 0, label);
-        break;
     case 3: /* cc: !C */
-        tcg_gen_brcondi_i32(TCG_COND_EQ, cpu_CF, 0, label);
+        cond = TCG_COND_NE;
+        value = cpu_CF;
         break;
+
     case 4: /* mi: N */
-        tcg_gen_brcondi_i32(TCG_COND_LT, cpu_NF, 0, label);
-        break;
     case 5: /* pl: !N */
-        tcg_gen_brcondi_i32(TCG_COND_GE, cpu_NF, 0, label);
+        cond = TCG_COND_LT;
+        value = cpu_NF;
         break;
+
     case 6: /* vs: V */
-        tcg_gen_brcondi_i32(TCG_COND_LT, cpu_VF, 0, label);
-        break;
     case 7: /* vc: !V */
-        tcg_gen_brcondi_i32(TCG_COND_GE, cpu_VF, 0, label);
+        cond = TCG_COND_LT;
+        value = cpu_VF;
         break;
+
     case 8: /* hi: C && !Z */
-        inv = gen_new_label();
-        tcg_gen_brcondi_i32(TCG_COND_EQ, cpu_CF, 0, inv);
-        tcg_gen_brcondi_i32(TCG_COND_NE, cpu_ZF, 0, label);
-        gen_set_label(inv);
-        break;
-    case 9: /* ls: !C || Z */
-        tcg_gen_brcondi_i32(TCG_COND_EQ, cpu_CF, 0, label);
-        tcg_gen_brcondi_i32(TCG_COND_EQ, cpu_ZF, 0, label);
+    case 9: /* ls: !C || Z -> !(C && !Z) */
+        cond = TCG_COND_NE;
+        value = tcg_temp_new_i32();
+        global = false;
+        /* CF is 1 for C, so -CF is an all-bits-set mask for C;
+           ZF is non-zero for !Z; so AND the two subexpressions.  */
+        tcg_gen_neg_i32(value, cpu_CF);
+        tcg_gen_and_i32(value, value, cpu_ZF);
         break;
+
     case 10: /* ge: N == V -> N ^ V == 0 */
-        tmp = tcg_temp_new_i32();
-        tcg_gen_xor_i32(tmp, cpu_VF, cpu_NF);
-        tcg_gen_brcondi_i32(TCG_COND_GE, tmp, 0, label);
-        tcg_temp_free_i32(tmp);
-        break;
     case 11: /* lt: N != V -> N ^ V != 0 */
-        tmp = tcg_temp_new_i32();
-        tcg_gen_xor_i32(tmp, cpu_VF, cpu_NF);
-        tcg_gen_brcondi_i32(TCG_COND_LT, tmp, 0, label);
-        tcg_temp_free_i32(tmp);
+        /* Since we're only interested in the sign bit, == 0 is >= 0.  */
+        cond = TCG_COND_GE;
+        value = tcg_temp_new_i32();
+        global = false;
+        tcg_gen_xor_i32(value, cpu_VF, cpu_NF);
         break;
+
     case 12: /* gt: !Z && N == V */
-        inv = gen_new_label();
-        tcg_gen_brcondi_i32(TCG_COND_EQ, cpu_ZF, 0, inv);
-        tmp = tcg_temp_new_i32();
-        tcg_gen_xor_i32(tmp, cpu_VF, cpu_NF);
-        tcg_gen_brcondi_i32(TCG_COND_GE, tmp, 0, label);
-        tcg_temp_free_i32(tmp);
-        gen_set_label(inv);
-        break;
     case 13: /* le: Z || N != V */
-        tcg_gen_brcondi_i32(TCG_COND_EQ, cpu_ZF, 0, label);
-        tmp = tcg_temp_new_i32();
-        tcg_gen_xor_i32(tmp, cpu_VF, cpu_NF);
-        tcg_gen_brcondi_i32(TCG_COND_LT, tmp, 0, label);
-        tcg_temp_free_i32(tmp);
+        cond = TCG_COND_NE;
+        value = tcg_temp_new_i32();
+        global = false;
+        /* (N == V) is equal to the sign bit of ~(NF ^ VF).  Propagate
+         * the sign bit then AND with ZF to yield the result.  */
+        tcg_gen_xor_i32(value, cpu_VF, cpu_NF);
+        tcg_gen_sari_i32(value, value, 31);
+        tcg_gen_andc_i32(value, cpu_ZF, value);
         break;
+
     default:
         fprintf(stderr, "Bad condition code 0x%x\n", cc);
         abort();
     }
+
+    if (cc & 1) {
+        cond = tcg_invert_cond(cond);
+    }
+
+    cmp->cond = cond;
+    cmp->value = value;
+    cmp->value_global = global;
+}
+
+void arm_free_cc(DisasCompare *cmp)
+{
+    if (!cmp->value_global) {
+        tcg_temp_free_i32(cmp->value);
+    }
+}
+
+void arm_jump_cc(DisasCompare *cmp, TCGLabel *label)
+{
+    tcg_gen_brcondi_i32(cmp->cond, cmp->value, 0, label);
+}
+
+void arm_gen_test_cc(int cc, TCGLabel *label)
+{
+    DisasCompare cmp;
+    arm_test_cc(&cmp, cc);
+    arm_jump_cc(&cmp, label);
+    arm_free_cc(&cmp);
 }
 
 static const uint8_t table_logic_cc[16] = {
diff --git a/target-arm/translate.h b/target-arm/translate.h
index a30a1db3..b8fe37a 100644
--- a/target-arm/translate.h
+++ b/target-arm/translate.h
@@ -63,6 +63,12 @@ typedef struct DisasContext {
     TCGv_i64 tmp_a64[TMP_A64_MAX];
 } DisasContext;
 
+typedef struct DisasCompare {
+    TCGCond cond;
+    TCGv_i32 value;
+    bool value_global;
+} DisasCompare;
+
 /* Share the TCG temporaries common between 32 and 64 bit modes.  */
 extern TCGv_ptr cpu_env;
 extern TCGv_i32 cpu_NF, cpu_ZF, cpu_CF, cpu_VF;
@@ -144,6 +150,9 @@ static inline void aarch64_cpu_dump_state(CPUState *cs, FILE *f,
 }
 #endif
 
+void arm_test_cc(DisasCompare *cmp, int cc);
+void arm_free_cc(DisasCompare *cmp);
+void arm_jump_cc(DisasCompare *cmp, TCGLabel *label);
 void arm_gen_test_cc(int cc, TCGLabel *label);
 
 #endif /* TARGET_ARM_TRANSLATE_H */
-- 
1.9.1