target/arm: Convert LDXP, STXP, CASP, CAS to decodetree

Convert the load/store exclusive pair (LDXP, STXP, LDAXP, STLXP),
compare-and-swap pair (CASP, CASPA, CASPAL, CASPL), and compare-and
swap (CAS, CASA, CASAL, CASL) instructions to decodetree.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20230602155223.2040685-10-peter.maydell@linaro.org

2 files changed, 50 insertions, 76 deletions

diff --git a/target/arm/tcg/a64.decode b/target/arm/tcg/a64.decode
index c5894fc..6b1079b 100644
--- a/target/arm/tcg/a64.decode
+++ b/target/arm/tcg/a64.decode
@@ -237,7 +237,18 @@ HLT             1101 0100 010 ................ 000 00 @i16
 &stlr           rn rt sz lasr
 @stxr           sz:2 ...... ... rs:5 lasr:1 rt2:5 rn:5 rt:5 &stxr
 @stlr           sz:2 ...... ... ..... lasr:1 ..... rn:5 rt:5 &stlr
+%imm1_30_p2 30:1 !function=plus_2
+@stxp           .. ...... ... rs:5 lasr:1 rt2:5 rn:5 rt:5 &stxr sz=%imm1_30_p2
 STXR            .. 001000 000 ..... . ..... ..... ..... @stxr  # inc STLXR
 LDXR            .. 001000 010 ..... . ..... ..... ..... @stxr  # inc LDAXR
 STLR            .. 001000 100 11111 . 11111 ..... ..... @stlr  # inc STLLR
 LDAR            .. 001000 110 11111 . 11111 ..... ..... @stlr  # inc LDLAR
+
+STXP            1 . 001000 001 ..... . ..... ..... ..... @stxp # inc STLXP
+LDXP            1 . 001000 011 ..... . ..... ..... ..... @stxp # inc LDAXP
+
+# CASP, CASPA, CASPAL, CASPL (we don't decode the bits that determine
+# acquire/release semantics because QEMU's cmpxchg always has those)
+CASP            0 . 001000 0 - 1 rs:5 - 11111 rn:5 rt:5 sz=%imm1_30_p2
+# CAS, CASA, CASAL, CASL
+CAS             sz:2 001000 1 - 1 rs:5 - 11111 rn:5 rt:5
diff --git a/target/arm/tcg/translate-a64.c b/target/arm/tcg/translate-a64.c
index 1ba2d6a..ff4338e 100644
--- a/target/arm/tcg/translate-a64.c
+++ b/target/arm/tcg/translate-a64.c
@@ -2741,84 +2741,50 @@ static bool trans_LDAR(DisasContext *s, arg_stlr *a)
     return true;
 }
 
-/* Load/store exclusive
- *
- *  31 30 29         24  23  22   21  20  16  15  14   10 9    5 4    0
- * +-----+-------------+----+---+----+------+----+-------+------+------+
- * | sz  | 0 0 1 0 0 0 | o2 | L | o1 |  Rs  | o0 |  Rt2  |  Rn  | Rt   |
- * +-----+-------------+----+---+----+------+----+-------+------+------+
- *
- *  sz: 00 -> 8 bit, 01 -> 16 bit, 10 -> 32 bit, 11 -> 64 bit
- *   L: 0 -> store, 1 -> load
- *  o2: 0 -> exclusive, 1 -> not
- *  o1: 0 -> single register, 1 -> register pair
- *  o0: 1 -> load-acquire/store-release, 0 -> not
- */
-static void disas_ldst_excl(DisasContext *s, uint32_t insn)
+static bool trans_STXP(DisasContext *s, arg_stxr *a)
 {
-    int rt = extract32(insn, 0, 5);
-    int rn = extract32(insn, 5, 5);
-    int rt2 = extract32(insn, 10, 5);
-    int rs = extract32(insn, 16, 5);
-    int is_lasr = extract32(insn, 15, 1);
-    int o2_L_o1_o0 = extract32(insn, 21, 3) * 2 | is_lasr;
-    int size = extract32(insn, 30, 2);
+    if (a->rn == 31) {
+        gen_check_sp_alignment(s);
+    }
+    if (a->lasr) {
+        tcg_gen_mb(TCG_MO_ALL | TCG_BAR_STRL);
+    }
+    gen_store_exclusive(s, a->rs, a->rt, a->rt2, a->rn, a->sz, true);
+    return true;
+}
 
-    switch (o2_L_o1_o0) {
-    case 0x2: case 0x3: /* CASP / STXP */
-        if (size & 2) { /* STXP / STLXP */
-            if (rn == 31) {
-                gen_check_sp_alignment(s);
-            }
-            if (is_lasr) {
-                tcg_gen_mb(TCG_MO_ALL | TCG_BAR_STRL);
-            }
-            gen_store_exclusive(s, rs, rt, rt2, rn, size, true);
-            return;
-        }
-        if (rt2 == 31
-            && ((rt | rs) & 1) == 0
-            && dc_isar_feature(aa64_atomics, s)) {
-            /* CASP / CASPL */
-            gen_compare_and_swap_pair(s, rs, rt, rn, size | 2);
-            return;
-        }
-        break;
+static bool trans_LDXP(DisasContext *s, arg_stxr *a)
+{
+    if (a->rn == 31) {
+        gen_check_sp_alignment(s);
+    }
+    gen_load_exclusive(s, a->rt, a->rt2, a->rn, a->sz, true);
+    if (a->lasr) {
+        tcg_gen_mb(TCG_MO_ALL | TCG_BAR_LDAQ);
+    }
+    return true;
+}
 
-    case 0x6: case 0x7: /* CASPA / LDXP */
-        if (size & 2) { /* LDXP / LDAXP */
-            if (rn == 31) {
-                gen_check_sp_alignment(s);
-            }
-            gen_load_exclusive(s, rt, rt2, rn, size, true);
-            if (is_lasr) {
-                tcg_gen_mb(TCG_MO_ALL | TCG_BAR_LDAQ);
-            }
-            return;
-        }
-        if (rt2 == 31
-            && ((rt | rs) & 1) == 0
-            && dc_isar_feature(aa64_atomics, s)) {
-            /* CASPA / CASPAL */
-            gen_compare_and_swap_pair(s, rs, rt, rn, size | 2);
-            return;
-        }
-        break;
+static bool trans_CASP(DisasContext *s, arg_CASP *a)
+{
+    if (!dc_isar_feature(aa64_atomics, s)) {
+        return false;
+    }
+    if (((a->rt | a->rs) & 1) != 0) {
+        return false;
+    }
 
-    case 0xa: /* CAS */
-    case 0xb: /* CASL */
-    case 0xe: /* CASA */
-    case 0xf: /* CASAL */
-        if (rt2 == 31 && dc_isar_feature(aa64_atomics, s)) {
-            gen_compare_and_swap(s, rs, rt, rn, size);
-            return;
-        }
-        break;
-    default:
-        /* Handled in decodetree */
-        break;
+    gen_compare_and_swap_pair(s, a->rs, a->rt, a->rn, a->sz);
+    return true;
+}
+
+static bool trans_CAS(DisasContext *s, arg_CAS *a)
+{
+    if (!dc_isar_feature(aa64_atomics, s)) {
+        return false;
     }
-    unallocated_encoding(s);
+    gen_compare_and_swap(s, a->rs, a->rt, a->rn, a->sz);
+    return true;
 }
 
 /*
@@ -4247,9 +4213,6 @@ static void disas_ldst_tag(DisasContext *s, uint32_t insn)
 static void disas_ldst(DisasContext *s, uint32_t insn)
 {
     switch (extract32(insn, 24, 6)) {
-    case 0x08: /* Load/store exclusive */
-        disas_ldst_excl(s, insn);
-        break;
     case 0x18: case 0x1c: /* Load register (literal) */
         disas_ld_lit(s, insn);
         break;