[Qemu-devel] [PATCH] target-arm: Implement ARMv8 VSEL instruction.

[Will Newton <will.newton@linaro.org>]

This adds support for the VSEL floating point selection instruction
which was added in ARMv8. It is based on the previous patch[1] from
Mans Rullgard, but attempts to addres the feedback given on that patch.

[1] http://lists.nongnu.org/archive/html/qemu-devel/2013-06/msg03117.html

Signed-off-by: Will Newton <will.newton@linaro.org>
---
 target-arm/translate.c | 121 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 121 insertions(+)

diff --git a/target-arm/translate.c b/target-arm/translate.c
index 998bde2..7bfd606 100644
--- a/target-arm/translate.c
+++ b/target-arm/translate.c
@@ -2617,6 +2617,114 @@ static TCGv_i32 gen_load_and_replicate(DisasContext *s, TCGv_i32 addr, int size)
     return tmp;
 }

+static int disas_v8vfp_insn(CPUARMState *env, DisasContext *s, uint32_t insn)
+{
+    uint32_t rd, rn, rm, dp = (insn >> 8) & 1;
+
+    if (!s->vfp_enabled)
+      return 1;
+
+    if (dp) {
+        VFP_DREG_D(rd, insn);
+        VFP_DREG_N(rn, insn);
+        VFP_DREG_M(rm, insn);
+    } else {
+        rd = VFP_SREG_D(insn);
+        rn = VFP_SREG_N(insn);
+        rm = VFP_SREG_M(insn);
+    }
+
+    if (((insn >> 23) & 1) == 0) {
+        /* vsel */
+        uint32_t cc = (insn >> 20) & 3;
+	TCGv_i32 tmp, zero;
+
+	zero = tcg_const_tl(0);
+
+	if (dp) {
+	    TCGv_i64 ftmp1, ftmp2, ftmp3;
+
+	    ftmp1 = tcg_temp_new_i64();
+	    ftmp2 = tcg_temp_new_i64();
+	    ftmp3 = tcg_temp_new_i64();
+	    tcg_gen_ld_f64(ftmp1, cpu_env, vfp_reg_offset(dp, rn));
+	    tcg_gen_ld_f64(ftmp2, cpu_env, vfp_reg_offset(dp, rm));
+	    switch (cc) {
+	    case 0: /* eq: Z */
+		tcg_gen_movcond_i64(TCG_COND_EQ, ftmp3, cpu_ZF, zero,
+				    ftmp1, ftmp2);
+		break;
+	    case 1: /* vs: V */
+		tcg_gen_movcond_i64(TCG_COND_LT, ftmp3, cpu_VF, zero,
+				    ftmp1, ftmp2);
+		break;
+	    case 2: /* ge: N == V -> N ^ V == 0 */
+		tmp = tcg_temp_new_i32();
+		tcg_gen_xor_i32(tmp, cpu_VF, cpu_NF);
+		tcg_gen_movcond_i64(TCG_COND_GE, ftmp3, tmp, zero,
+				    ftmp1, ftmp2);
+		tcg_temp_free_i32(tmp);
+		break;
+	    case 3: /* gt: !Z && N == V */
+		tcg_gen_movcond_i64(TCG_COND_NE, ftmp3, cpu_ZF, zero,
+				    ftmp1, ftmp2);
+		tmp = tcg_temp_new_i32();
+		tcg_gen_xor_i32(tmp, cpu_VF, cpu_NF);
+		tcg_gen_movcond_i64(TCG_COND_GE, ftmp3, tmp, zero,
+				    ftmp3, ftmp2);
+		tcg_temp_free_i32(tmp);
+		break;
+	    }
+	    tcg_gen_st_f64(ftmp3, cpu_env, vfp_reg_offset(dp, rd));
+	    tcg_temp_free_i64(ftmp1);
+	    tcg_temp_free_i64(ftmp2);
+	    tcg_temp_free_i64(ftmp3);
+	} else {
+	    TCGv_i32 ftmp1, ftmp2, ftmp3;
+
+	    ftmp1 = tcg_temp_new_i32();
+	    ftmp2 = tcg_temp_new_i32();
+	    ftmp3 = tcg_temp_new_i32();
+	    tcg_gen_ld_f32(ftmp1, cpu_env, vfp_reg_offset(dp, rn));
+	    tcg_gen_ld_f32(ftmp2, cpu_env, vfp_reg_offset(dp, rm));
+	    switch (cc) {
+	    case 0: /* eq: Z */
+		tcg_gen_movcond_i32(TCG_COND_EQ, ftmp3, cpu_ZF, zero,
+				    ftmp1, ftmp2);
+		break;
+	    case 1: /* vs: V */
+		tcg_gen_movcond_i32(TCG_COND_LT, ftmp3, cpu_VF, zero,
+				    ftmp1, ftmp2);
+		break;
+	    case 2: /* ge: N == V -> N ^ V == 0 */
+		tmp = tcg_temp_new_i32();
+		tcg_gen_xor_i32(tmp, cpu_VF, cpu_NF);
+		tcg_gen_movcond_i32(TCG_COND_GE, ftmp3, tmp, zero,
+				    ftmp1, ftmp2);
+		tcg_temp_free_i32(tmp);
+		break;
+	    case 3: /* gt: !Z && N == V */
+		tcg_gen_movcond_i32(TCG_COND_NE, ftmp3, cpu_ZF, zero,
+				    ftmp1, ftmp2);
+		tmp = tcg_temp_new_i32();
+		tcg_gen_xor_i32(tmp, cpu_VF, cpu_NF);
+		tcg_gen_movcond_i32(TCG_COND_GE, ftmp3, tmp, zero,
+				    ftmp3, ftmp2);
+		tcg_temp_free_i32(tmp);
+		break;
+	    }
+	    tcg_gen_st_f32(ftmp3, cpu_env, vfp_reg_offset(dp, rd));
+	    tcg_temp_free_i32(ftmp1);
+	    tcg_temp_free_i32(ftmp2);
+	    tcg_temp_free_i32(ftmp3);
+	}
+
+        return 0;
+    }
+
+    return 1;
+}
+
 /* Disassemble a VFP instruction.  Returns nonzero if an error occurred
    (ie. an undefined instruction).  */
 static int disas_vfp_insn(CPUARMState * env, DisasContext *s, uint32_t insn)
@@ -6756,6 +6864,13 @@ static void disas_arm_insn(CPUARMState * env, DisasContext *s)
                 goto illegal_op;
             return;
         }
+	if ((insn & 0x0f800e50) == 0x0e000a00) {
+	    /* ARMv8 VFP.  */
+	    ARCH(8);
+
+	    if (disas_v8vfp_insn(env, s, insn))
+		goto illegal_op;
+	}
         if (((insn & 0x0f30f000) == 0x0510f000) ||
             ((insn & 0x0f30f010) == 0x0710f000)) {
             if ((insn & (1 << 22)) == 0) {
@@ -8768,6 +8883,12 @@ static int disas_thumb2_insn(CPUARMState *env, DisasContext *s, uint16_t insn_hw
             insn = (insn & 0xe2ffffff) | ((insn & (1 << 28)) >> 4) | (1 << 28);
             if (disas_neon_data_insn(env, s, insn))
                 goto illegal_op;
+	} else if ((insn & 0x0f800e50) == 0x0e000a00) {
+	    /* ARMv8 VFP.  */
+	    ARCH(8);
+
+	    if (disas_v8vfp_insn(env, s, insn))
+		goto illegal_op;
         } else {
             if (insn & (1 << 28))
                 goto illegal_op;
-- 
1.8.1.4