[Qemu-devel] [PATCH 06/16] target-arm: A64: Saturating and narrowing shift ops

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

From: Alex Bennée <alex.bennee@linaro.org>

This implements a the remaining [US][R]SHR[R][2] opcodes which are
saturating and narrowing shift right operations. These are used in
things like libav. Note signed shifts can have an "unsigned" saturating
narrow operation which will floor negative values.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
[PMM: Added the scalar encodings, style tweaks]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target-arm/translate-a64.c | 181 ++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 178 insertions(+), 3 deletions(-)

diff --git a/target-arm/translate-a64.c b/target-arm/translate-a64.c
index 0c2b903..eff7a7d 100644
--- a/target-arm/translate-a64.c
+++ b/target-arm/translate-a64.c
@@ -5907,6 +5907,94 @@ static void handle_scalar_simd_shli(DisasContext *s, bool insert,
     tcg_temp_free_i64(tcg_rd);
 }
 
+/* SQSHRN/SQSHRUN - Saturating (signed/unsigned) shift right with
+ * (signed/unsigned) narrowing */
+static void handle_vec_simd_sqshrn(DisasContext *s, bool is_scalar, bool is_q,
+                                   bool is_u_shift, bool is_u_narrow,
+                                   int immh, int immb, int opcode,
+                                   int rn, int rd)
+{
+    int immhb = immh << 3 | immb;
+    int size = 32 - clz32(immh) - 1;
+    int esize = 8 << size;
+    int shift = (2 * esize) - immhb;
+    int elements = is_scalar ? 1 : (64 / esize);
+    bool round = extract32(opcode, 0, 1);
+    TCGMemOp ldop = (size + 1) | (is_u_shift ? 0 : MO_SIGN);
+    TCGv_i64 tcg_rn, tcg_rd, tcg_round;
+    TCGv_i32 tcg_rd_narrowed;
+    TCGv_i64 tcg_final;
+
+    static NeonGenNarrowEnvFn * const signed_narrow_fns[4][2] = {
+        { gen_helper_neon_narrow_sat_s8,
+          gen_helper_neon_unarrow_sat8 },
+        { gen_helper_neon_narrow_sat_s16,
+          gen_helper_neon_unarrow_sat16 },
+        { gen_helper_neon_narrow_sat_s32,
+          gen_helper_neon_unarrow_sat32 },
+        { NULL, NULL },
+    };
+    static NeonGenNarrowEnvFn * const unsigned_narrow_fns[4] = {
+        gen_helper_neon_narrow_sat_u8,
+        gen_helper_neon_narrow_sat_u16,
+        gen_helper_neon_narrow_sat_u32,
+        NULL
+    };
+    NeonGenNarrowEnvFn *narrowfn;
+
+    int i;
+
+    assert(size < 4);
+
+    if (extract32(immh, 3, 1)) {
+        unallocated_encoding(s);
+        return;
+    }
+
+    if (is_u_shift) {
+        narrowfn = unsigned_narrow_fns[size];
+    } else {
+        narrowfn = signed_narrow_fns[size][is_u_narrow ? 1 : 0];
+    }
+
+    tcg_rn = tcg_temp_new_i64();
+    tcg_rd = tcg_temp_new_i64();
+    tcg_rd_narrowed = tcg_temp_new_i32();
+    tcg_final = tcg_const_i64(0);
+
+    if (round) {
+        uint64_t round_const = 1ULL << (shift - 1);
+        tcg_round = tcg_const_i64(round_const);
+    } else {
+        TCGV_UNUSED_I64(tcg_round);
+    }
+
+    for (i = 0; i < elements; i++) {
+        read_vec_element(s, tcg_rn, rn, i, ldop);
+        handle_shri_with_rndacc(tcg_rd, tcg_rn, tcg_round,
+                                false, is_u_shift, size+1, shift);
+        narrowfn(tcg_rd_narrowed, cpu_env, tcg_rd);
+        tcg_gen_extu_i32_i64(tcg_rd, tcg_rd_narrowed);
+        tcg_gen_deposit_i64(tcg_final, tcg_final, tcg_rd, esize * i, esize);
+    }
+
+    if (!is_q) {
+        clear_vec_high(s, rd);
+        write_vec_element(s, tcg_final, rd, 0, MO_64);
+    } else {
+        write_vec_element(s, tcg_final, rd, 1, MO_64);
+    }
+
+    if (round) {
+        tcg_temp_free_i64(tcg_round);
+    }
+    tcg_temp_free_i64(tcg_rn);
+    tcg_temp_free_i64(tcg_rd);
+    tcg_temp_free_i32(tcg_rd_narrowed);
+    tcg_temp_free_i64(tcg_final);
+    return;
+}
+
 /* Common vector code for handling integer to FP conversion */
 static void handle_simd_intfp_conv(DisasContext *s, int rd, int rn,
                                    int elements, int is_signed,
@@ -6013,6 +6101,11 @@ static void disas_simd_scalar_shift_imm(DisasContext *s, uint32_t insn)
     int immh = extract32(insn, 19, 4);
     bool is_u = extract32(insn, 29, 1);
 
+    if (immh == 0) {
+        unallocated_encoding(s);
+        return;
+    }
+
     switch (opcode) {
     case 0x00: /* SSHR / USHR */
     case 0x02: /* SSRA / USRA */
@@ -6027,6 +6120,20 @@ static void disas_simd_scalar_shift_imm(DisasContext *s, uint32_t insn)
         handle_simd_shift_intfp_conv(s, true, false, is_u, immh, immb,
                                      opcode, rn, rd);
         break;
+    case 0x10: /* SQSHRUN, SQSHRUN2 */
+    case 0x11: /* SQRSHRUN, SQRSHRUN2 */
+        if (!is_u) {
+            unallocated_encoding(s);
+            return;
+        }
+        handle_vec_simd_sqshrn(s, true, false, false, true,
+                               immh, immb, opcode, rn, rd);
+        break;
+    case 0x12: /* SQSHRN, SQSHRN2, UQSHRN */
+    case 0x13: /* SQRSHRN, SQRSHRN2, UQRSHRN, UQRSHRN2 */
+        handle_vec_simd_sqshrn(s, true, false, is_u, is_u,
+                               immh, immb, opcode, rn, rd);
+        break;
     default:
         unsupported_encoding(s, insn);
         break;
@@ -6985,6 +7092,63 @@ static void handle_vec_simd_wshli(DisasContext *s, bool is_q, bool is_u,
     }
 }
 
+/* SHRN/RSHRN - Shift right with narrowing (and potential rounding) */
+static void handle_vec_simd_shrn(DisasContext *s, bool is_q,
+                                 int immh, int immb, int opcode, int rn, int rd)
+{
+    int immhb = immh << 3 | immb;
+    int size = 32 - clz32(immh) - 1;
+    int dsize = 64;
+    int esize = 8 << size;
+    int elements = dsize/esize;
+    int shift = (2 * esize) - immhb;
+    bool round = extract32(opcode, 0, 1);
+    TCGv_i64 tcg_rn, tcg_rd, tcg_final;
+    TCGv_i64 tcg_round;
+    int i;
+
+    if (extract32(immh, 3, 1)) {
+        unallocated_encoding(s);
+        return;
+    }
+
+    tcg_rn = tcg_temp_new_i64();
+    tcg_rd = tcg_temp_new_i64();
+    tcg_final = tcg_temp_new_i64();
+    read_vec_element(s, tcg_final, rd, is_q ? 1 : 0, MO_64);
+
+    if (round) {
+        uint64_t round_const = 1ULL << (shift - 1);
+        tcg_round = tcg_const_i64(round_const);
+    } else {
+        TCGV_UNUSED_I64(tcg_round);
+    }
+
+    for (i = 0; i < elements; i++) {
+        read_vec_element(s, tcg_rn, rn, i, size+1);
+        handle_shri_with_rndacc(tcg_rd, tcg_rn, tcg_round,
+                                false, true, size+1, shift);
+
+        tcg_gen_deposit_i64(tcg_final, tcg_final, tcg_rd, esize * i, esize);
+    }
+
+    if (!is_q) {
+        clear_vec_high(s, rd);
+        write_vec_element(s, tcg_final, rd, 0, MO_64);
+    } else {
+        write_vec_element(s, tcg_final, rd, 1, MO_64);
+    }
+
+    if (round) {
+        tcg_temp_free_i64(tcg_round);
+    }
+    tcg_temp_free_i64(tcg_rn);
+    tcg_temp_free_i64(tcg_rd);
+    tcg_temp_free_i64(tcg_final);
+    return;
+}
+
+
 /* C3.6.14 AdvSIMD shift by immediate
  *  31  30   29 28         23 22  19 18  16 15    11  10 9    5 4    0
  * +---+---+---+-------------+------+------+--------+---+------+------+
@@ -7011,6 +7175,20 @@ static void disas_simd_shift_imm(DisasContext *s, uint32_t insn)
     case 0x0a: /* SHL / SLI */
         handle_vec_simd_shli(s, is_q, is_u, immh, immb, opcode, rn, rd);
         break;
+    case 0x10: /* SHRN */
+    case 0x11: /* RSHRN / SQRSHRUN */
+        if (is_u) {
+            handle_vec_simd_sqshrn(s, false, is_q, false, true, immh, immb,
+                                   opcode, rn, rd);
+        } else {
+            handle_vec_simd_shrn(s, is_q, immh, immb, opcode, rn, rd);
+        }
+        break;
+    case 0x12: /* SQSHRN / UQSHRN */
+    case 0x13: /* SQRSHRN / UQRSHRN */
+        handle_vec_simd_sqshrn(s, false, is_q, is_u, is_u, immh, immb,
+                               opcode, rn, rd);
+        break;
     case 0x14: /* SSHLL / USHLL */
         handle_vec_simd_wshli(s, is_q, is_u, immh, immb, opcode, rn, rd);
         break;
@@ -7022,9 +7200,6 @@ static void disas_simd_shift_imm(DisasContext *s, uint32_t insn)
         unsupported_encoding(s, insn);
         return;
     default:
-        /* We don't currently implement any of the Narrow or
-         * saturating shifts.
-         */
         unsupported_encoding(s, insn);
         return;
     }
-- 
1.9.0