target/arm: Convert Neon VSHR 2-reg-shift insns to decodetree

Convert the VSHR 2-reg-shift insns to decodetree.

Note that unlike the legacy decoder, we present the right shift
amount to the trans_ function as a positive integer.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20200522145520.6778-3-peter.maydell@linaro.org

3 files changed, 67 insertions, 20 deletions

diff --git a/target/arm/neon-dp.decode b/target/arm/neon-dp.decode
index fcce2edacd..1b877cc68f 100644
--- a/target/arm/neon-dp.decode
+++ b/target/arm/neon-dp.decode
@@ -208,6 +208,21 @@ VMINNM_fp_3s     1111 001 1 0 . 1 . .... .... 1111 ... 1 .... @3same_fp
 ######################################################################
 &2reg_shift vm vd q shift size
 
+# Right shifts are encoded as N - shift, where N is the element size in bits.
+%neon_rshift_i6  16:6 !function=rsub_64
+%neon_rshift_i5  16:5 !function=rsub_32
+%neon_rshift_i4  16:4 !function=rsub_16
+%neon_rshift_i3  16:3 !function=rsub_8
+
+@2reg_shr_d      .... ... . . . ......  .... .... 1 q:1 . . .... \
+                 &2reg_shift vm=%vm_dp vd=%vd_dp size=3 shift=%neon_rshift_i6
+@2reg_shr_s      .... ... . . . 1 ..... .... .... 0 q:1 . . .... \
+                 &2reg_shift vm=%vm_dp vd=%vd_dp size=2 shift=%neon_rshift_i5
+@2reg_shr_h      .... ... . . . 01 .... .... .... 0 q:1 . . .... \
+                 &2reg_shift vm=%vm_dp vd=%vd_dp size=1 shift=%neon_rshift_i4
+@2reg_shr_b      .... ... . . . 001 ... .... .... 0 q:1 . . .... \
+                 &2reg_shift vm=%vm_dp vd=%vd_dp size=0 shift=%neon_rshift_i3
+
 @2reg_shl_d      .... ... . . . shift:6      .... .... 1 q:1 . . .... \
                  &2reg_shift vm=%vm_dp vd=%vd_dp size=3
 @2reg_shl_s      .... ... . . . 1 shift:5    .... .... 0 q:1 . . .... \
@@ -217,6 +232,16 @@ VMINNM_fp_3s     1111 001 1 0 . 1 . .... .... 1111 ... 1 .... @3same_fp
 @2reg_shl_b      .... ... . . . 001 shift:3  .... .... 0 q:1 . . .... \
                  &2reg_shift vm=%vm_dp vd=%vd_dp size=0
 
+VSHR_S_2sh       1111 001 0 1 . ...... .... 0000 . . . 1 .... @2reg_shr_d
+VSHR_S_2sh       1111 001 0 1 . ...... .... 0000 . . . 1 .... @2reg_shr_s
+VSHR_S_2sh       1111 001 0 1 . ...... .... 0000 . . . 1 .... @2reg_shr_h
+VSHR_S_2sh       1111 001 0 1 . ...... .... 0000 . . . 1 .... @2reg_shr_b
+
+VSHR_U_2sh       1111 001 1 1 . ...... .... 0000 . . . 1 .... @2reg_shr_d
+VSHR_U_2sh       1111 001 1 1 . ...... .... 0000 . . . 1 .... @2reg_shr_s
+VSHR_U_2sh       1111 001 1 1 . ...... .... 0000 . . . 1 .... @2reg_shr_h
+VSHR_U_2sh       1111 001 1 1 . ...... .... 0000 . . . 1 .... @2reg_shr_b
+
 VSHL_2sh         1111 001 0 1 . ...... .... 0101 . . . 1 .... @2reg_shl_d
 VSHL_2sh         1111 001 0 1 . ...... .... 0101 . . . 1 .... @2reg_shl_s
 VSHL_2sh         1111 001 0 1 . ...... .... 0101 . . . 1 .... @2reg_shl_h
diff --git a/target/arm/translate-neon.inc.c b/target/arm/translate-neon.inc.c
index 7f05323fdf..8693b9aa99 100644
--- a/target/arm/translate-neon.inc.c
+++ b/target/arm/translate-neon.inc.c
@@ -31,6 +31,24 @@ static inline int plus1(DisasContext *s, int x)
     return x + 1;
 }
 
+static inline int rsub_64(DisasContext *s, int x)
+{
+    return 64 - x;
+}
+
+static inline int rsub_32(DisasContext *s, int x)
+{
+    return 32 - x;
+}
+static inline int rsub_16(DisasContext *s, int x)
+{
+    return 16 - x;
+}
+static inline int rsub_8(DisasContext *s, int x)
+{
+    return 8 - x;
+}
+
 /* Include the generated Neon decoder */
 #include "decode-neon-dp.inc.c"
 #include "decode-neon-ls.inc.c"
@@ -1240,3 +1258,26 @@ static bool do_vector_2sh(DisasContext *s, arg_2reg_shift *a, GVecGen2iFn *fn)
 
 DO_2SH(VSHL, tcg_gen_gvec_shli)
 DO_2SH(VSLI, gen_gvec_sli)
+
+static bool trans_VSHR_S_2sh(DisasContext *s, arg_2reg_shift *a)
+{
+    /* Signed shift out of range results in all-sign-bits */
+    a->shift = MIN(a->shift, (8 << a->size) - 1);
+    return do_vector_2sh(s, a, tcg_gen_gvec_sari);
+}
+
+static void gen_zero_rd_2sh(unsigned vece, uint32_t rd_ofs, uint32_t rm_ofs,
+                            int64_t shift, uint32_t oprsz, uint32_t maxsz)
+{
+    tcg_gen_gvec_dup_imm(vece, rd_ofs, oprsz, maxsz, 0);
+}
+
+static bool trans_VSHR_U_2sh(DisasContext *s, arg_2reg_shift *a)
+{
+    /* Shift out of range is architecturally valid and results in zero. */
+    if (a->shift >= (8 << a->size)) {
+        return do_vector_2sh(s, a, gen_zero_rd_2sh);
+    } else {
+        return do_vector_2sh(s, a, tcg_gen_gvec_shri);
+    }
+}
diff --git a/target/arm/translate.c b/target/arm/translate.c
index 41fef49dbe..4acc94e3cb 100644
--- a/target/arm/translate.c
+++ b/target/arm/translate.c
@@ -5296,6 +5296,7 @@ static int disas_neon_data_insn(DisasContext *s, uint32_t insn)
             op = (insn >> 8) & 0xf;
 
             switch (op) {
+            case 0: /* VSHR */
             case 5: /* VSHL, VSLI */
                 return 1; /* handled by decodetree */
             default:
@@ -5330,26 +5331,6 @@ static int disas_neon_data_insn(DisasContext *s, uint32_t insn)
                 }
 
                 switch (op) {
-                case 0:  /* VSHR */
-                    /* Right shift comes here negative.  */
-                    shift = -shift;
-                    /* Shifts larger than the element size are architecturally
-                     * valid.  Unsigned results in all zeros; signed results
-                     * in all sign bits.
-                     */
-                    if (!u) {
-                        tcg_gen_gvec_sari(size, rd_ofs, rm_ofs,
-                                          MIN(shift, (8 << size) - 1),
-                                          vec_size, vec_size);
-                    } else if (shift >= 8 << size) {
-                        tcg_gen_gvec_dup_imm(MO_8, rd_ofs, vec_size,
-                                             vec_size, 0);
-                    } else {
-                        tcg_gen_gvec_shri(size, rd_ofs, rm_ofs, shift,
-                                          vec_size, vec_size);
-                    }
-                    return 0;
-
                 case 1:  /* VSRA */
                     /* Right shift comes here negative.  */
                     shift = -shift;