include/exec/memop: Add MO_ATOM_*

This field may be used to describe the precise atomicity requirements
of the guest, which may then be used to constrain the methods by which
it may be emulated by the host.

For instance, the AArch64 LDP (32-bit) instruction changes semantics
with ARMv8.4 LSE2, from

  MO_64 | MO_ATOM_IFALIGN_PAIR
  (64-bits, single-copy atomic only on 4 byte units,
   nonatomic if not aligned by 4),

to

  MO_64 | MO_ATOM_WITHIN16
  (64-bits, single-copy atomic within a 16 byte block)

The former may be implemented with two 4 byte loads, or a single 8 byte
load if that happens to be efficient on the host.  The latter may not
be implemented with two 4 byte loads and may also require a helper when
misaligned.

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

1 files changed, 21 insertions, 6 deletions

diff --git a/tcg/tcg.c b/tcg/tcg.c
index 1231c8ab4c..f156ca65f5 100644
--- a/tcg/tcg.c
+++ b/tcg/tcg.c
@@ -2195,6 +2195,15 @@ static const char * const alignment_name[(MO_AMASK >> MO_ASHIFT) + 1] = {
     [MO_ALIGN_64 >> MO_ASHIFT] = "al64+",
 };
 
+static const char * const atom_name[(MO_ATOM_MASK >> MO_ATOM_SHIFT) + 1] = {
+    [MO_ATOM_IFALIGN >> MO_ATOM_SHIFT] = "",
+    [MO_ATOM_IFALIGN_PAIR >> MO_ATOM_SHIFT] = "pair+",
+    [MO_ATOM_WITHIN16 >> MO_ATOM_SHIFT] = "w16+",
+    [MO_ATOM_WITHIN16_PAIR >> MO_ATOM_SHIFT] = "w16p+",
+    [MO_ATOM_SUBALIGN >> MO_ATOM_SHIFT] = "sub+",
+    [MO_ATOM_NONE >> MO_ATOM_SHIFT] = "noat+",
+};
+
 static const char bswap_flag_name[][6] = {
     [TCG_BSWAP_IZ] = "iz",
     [TCG_BSWAP_OZ] = "oz",
@@ -2330,17 +2339,23 @@ static void tcg_dump_ops(TCGContext *s, FILE *f, bool have_prefs)
             case INDEX_op_qemu_ld_i64:
             case INDEX_op_qemu_st_i64:
                 {
+                    const char *s_al, *s_op, *s_at;
                     MemOpIdx oi = op->args[k++];
                     MemOp op = get_memop(oi);
                     unsigned ix = get_mmuidx(oi);
 
-                    if (op & ~(MO_AMASK | MO_BSWAP | MO_SSIZE)) {
-                        col += ne_fprintf(f, ",$0x%x,%u", op, ix);
+                    s_al = alignment_name[(op & MO_AMASK) >> MO_ASHIFT];
+                    s_op = ldst_name[op & (MO_BSWAP | MO_SSIZE)];
+                    s_at = atom_name[(op & MO_ATOM_MASK) >> MO_ATOM_SHIFT];
+                    op &= ~(MO_AMASK | MO_BSWAP | MO_SSIZE | MO_ATOM_MASK);
+
+                    /* If all fields are accounted for, print symbolically. */
+                    if (!op && s_al && s_op && s_at) {
+                        col += ne_fprintf(f, ",%s%s%s,%u",
+                                          s_at, s_al, s_op, ix);
                     } else {
-                        const char *s_al, *s_op;
-                        s_al = alignment_name[(op & MO_AMASK) >> MO_ASHIFT];
-                        s_op = ldst_name[op & (MO_BSWAP | MO_SSIZE)];
-                        col += ne_fprintf(f, ",%s%s,%u", s_al, s_op, ix);
+                        op = get_memop(oi);
+                        col += ne_fprintf(f, ",$0x%x,%u", op, ix);
                     }
                     i = 1;
                 }