diff options
author | Richard Henderson <richard.henderson@linaro.org> | 2022-11-08 09:23:54 +1100 |
---|---|---|
committer | Richard Henderson <richard.henderson@linaro.org> | 2023-05-16 16:30:29 -0700 |
commit | e63b8a29834d7fcc5574288852f78a5c70f19015 (patch) | |
tree | bf6ed1712af7b9f87f20f59fa370c60fda37de04 | |
parent | ebebea53ef8b08deb1ff970eaae706504a857bf6 (diff) |
tcg: Introduce atom_and_align_for_opc
Examine MemOp for atomicity and alignment, adjusting alignment
as required to implement atomicity on the host.
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
-rw-r--r-- | tcg/tcg.c | 95 |
1 files changed, 95 insertions, 0 deletions
@@ -220,6 +220,15 @@ static void * const qemu_st_helpers[MO_SIZE + 1] __attribute__((unused)) = { #endif }; +typedef struct { + MemOp atom; /* lg2 bits of atomicity required */ + MemOp align; /* lg2 bits of alignment to use */ +} TCGAtomAlign; + +static TCGAtomAlign atom_and_align_for_opc(TCGContext *s, MemOp opc, + MemOp host_atom, bool allow_two_ops) + __attribute__((unused)); + TCGContext tcg_init_ctx; __thread TCGContext *tcg_ctx; @@ -5230,6 +5239,92 @@ static void tcg_reg_alloc_call(TCGContext *s, TCGOp *op) } } +/** + * atom_and_align_for_opc: + * @s: tcg context + * @opc: memory operation code + * @host_atom: MO_ATOM_{IFALIGN,WITHIN16,SUBALIGN} for host operations + * @allow_two_ops: true if we are prepared to issue two operations + * + * Return the alignment and atomicity to use for the inline fast path + * for the given memory operation. The alignment may be larger than + * that specified in @opc, and the correct alignment will be diagnosed + * by the slow path helper. + * + * If @allow_two_ops, the host is prepared to test for 2x alignment, + * and issue two loads or stores for subalignment. + */ +static TCGAtomAlign atom_and_align_for_opc(TCGContext *s, MemOp opc, + MemOp host_atom, bool allow_two_ops) +{ + MemOp align = get_alignment_bits(opc); + MemOp size = opc & MO_SIZE; + MemOp half = size ? size - 1 : 0; + MemOp atmax; + MemOp atom; + + /* When serialized, no further atomicity required. */ + if (s->gen_tb->cflags & CF_PARALLEL) { + atom = opc & MO_ATOM_MASK; + } else { + atom = MO_ATOM_NONE; + } + + switch (atom) { + case MO_ATOM_NONE: + /* The operation requires no specific atomicity. */ + atmax = MO_8; + break; + + case MO_ATOM_IFALIGN: + atmax = size; + break; + + case MO_ATOM_IFALIGN_PAIR: + atmax = half; + break; + + case MO_ATOM_WITHIN16: + atmax = size; + if (size == MO_128) { + /* Misalignment implies !within16, and therefore no atomicity. */ + } else if (host_atom != MO_ATOM_WITHIN16) { + /* The host does not implement within16, so require alignment. */ + align = MAX(align, size); + } + break; + + case MO_ATOM_WITHIN16_PAIR: + atmax = size; + /* + * Misalignment implies !within16, and therefore half atomicity. + * Any host prepared for two operations can implement this with + * half alignment. + */ + if (host_atom != MO_ATOM_WITHIN16 && allow_two_ops) { + align = MAX(align, half); + } + break; + + case MO_ATOM_SUBALIGN: + atmax = size; + if (host_atom != MO_ATOM_SUBALIGN) { + /* If unaligned but not odd, there are subobjects up to half. */ + if (allow_two_ops) { + align = MAX(align, half); + } else { + align = MAX(align, size); + } + } + break; + + default: + g_assert_not_reached(); + } + + return (TCGAtomAlign){ .atom = atmax, .align = align }; +} + /* * Similarly for qemu_ld/st slow path helpers. * We must re-implement tcg_gen_callN and tcg_reg_alloc_call simultaneously, |