From fae450ba4764dcf8c7a131131639ac0969a8eae8 Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Wed, 25 Aug 2021 22:42:19 -0700 Subject: [PATCH] tcg/optimize: Split out fold_masks MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Move all of the known-zero optimizations into the per-opcode functions. Use fold_masks when there is a possibility of the result being determined, and simply set ctx->z_mask otherwise. Reviewed-by: Alex Bennée Reviewed-by: Luis Pires Signed-off-by: Richard Henderson --- tcg/optimize.c | 545 ++++++++++++++++++++++++++----------------------- 1 file changed, 294 insertions(+), 251 deletions(-) diff --git a/tcg/optimize.c b/tcg/optimize.c index bf74b77355..e84d10be53 100644 --- a/tcg/optimize.c +++ b/tcg/optimize.c @@ -50,7 +50,8 @@ typedef struct OptContext { TCGTempSet temps_used; /* In flight values from optimization. */ - uint64_t z_mask; + uint64_t a_mask; /* mask bit is 0 iff value identical to first input */ + uint64_t z_mask; /* mask bit is 0 iff value bit is 0 */ TCGType type; } OptContext; @@ -694,6 +695,31 @@ static bool fold_const2(OptContext *ctx, TCGOp *op) return false; } +static bool fold_masks(OptContext *ctx, TCGOp *op) +{ + uint64_t a_mask = ctx->a_mask; + uint64_t z_mask = ctx->z_mask; + + /* + * 32-bit ops generate 32-bit results. For the result is zero test + * below, we can ignore high bits, but for further optimizations we + * need to record that the high bits contain garbage. + */ + if (ctx->type == TCG_TYPE_I32) { + ctx->z_mask |= MAKE_64BIT_MASK(32, 32); + a_mask &= MAKE_64BIT_MASK(0, 32); + z_mask &= MAKE_64BIT_MASK(0, 32); + } + + if (z_mask == 0) { + return tcg_opt_gen_movi(ctx, op, op->args[0], 0); + } + if (a_mask == 0) { + return tcg_opt_gen_mov(ctx, op, op->args[0], op->args[1]); + } + return false; +} + /* * Convert @op to NOT, if NOT is supported by the host. * Return true f the conversion is successful, which will still @@ -847,24 +873,55 @@ static bool fold_add2_i32(OptContext *ctx, TCGOp *op) static bool fold_and(OptContext *ctx, TCGOp *op) { + uint64_t z1, z2; + if (fold_const2(ctx, op) || fold_xi_to_i(ctx, op, 0) || fold_xi_to_x(ctx, op, -1) || fold_xx_to_x(ctx, op)) { return true; } - return false; + + z1 = arg_info(op->args[1])->z_mask; + z2 = arg_info(op->args[2])->z_mask; + ctx->z_mask = z1 & z2; + + /* + * Known-zeros does not imply known-ones. Therefore unless + * arg2 is constant, we can't infer affected bits from it. + */ + if (arg_is_const(op->args[2])) { + ctx->a_mask = z1 & ~z2; + } + + return fold_masks(ctx, op); } static bool fold_andc(OptContext *ctx, TCGOp *op) { + uint64_t z1; + if (fold_const2(ctx, op) || fold_xx_to_i(ctx, op, 0) || fold_xi_to_x(ctx, op, 0) || fold_ix_to_not(ctx, op, -1)) { return true; } - return false; + + z1 = arg_info(op->args[1])->z_mask; + + /* + * Known-zeros does not imply known-ones. Therefore unless + * arg2 is constant, we can't infer anything from it. + */ + if (arg_is_const(op->args[2])) { + uint64_t z2 = ~arg_info(op->args[2])->z_mask; + ctx->a_mask = z1 & ~z2; + z1 &= z2; + } + ctx->z_mask = z1; + + return fold_masks(ctx, op); } static bool fold_brcond(OptContext *ctx, TCGOp *op) @@ -963,13 +1020,52 @@ static bool fold_brcond2(OptContext *ctx, TCGOp *op) static bool fold_bswap(OptContext *ctx, TCGOp *op) { + uint64_t z_mask, sign; + if (arg_is_const(op->args[1])) { uint64_t t = arg_info(op->args[1])->val; t = do_constant_folding(op->opc, ctx->type, t, op->args[2]); return tcg_opt_gen_movi(ctx, op, op->args[0], t); } - return false; + + z_mask = arg_info(op->args[1])->z_mask; + switch (op->opc) { + case INDEX_op_bswap16_i32: + case INDEX_op_bswap16_i64: + z_mask = bswap16(z_mask); + sign = INT16_MIN; + break; + case INDEX_op_bswap32_i32: + case INDEX_op_bswap32_i64: + z_mask = bswap32(z_mask); + sign = INT32_MIN; + break; + case INDEX_op_bswap64_i64: + z_mask = bswap64(z_mask); + sign = INT64_MIN; + break; + default: + g_assert_not_reached(); + } + + switch (op->args[2] & (TCG_BSWAP_OZ | TCG_BSWAP_OS)) { + case TCG_BSWAP_OZ: + break; + case TCG_BSWAP_OS: + /* If the sign bit may be 1, force all the bits above to 1. */ + if (z_mask & sign) { + z_mask |= sign; + } + break; + default: + /* The high bits are undefined: force all bits above the sign to 1. */ + z_mask |= sign << 1; + break; + } + ctx->z_mask = z_mask; + + return fold_masks(ctx, op); } static bool fold_call(OptContext *ctx, TCGOp *op) @@ -1006,6 +1102,8 @@ static bool fold_call(OptContext *ctx, TCGOp *op) static bool fold_count_zeros(OptContext *ctx, TCGOp *op) { + uint64_t z_mask; + if (arg_is_const(op->args[1])) { uint64_t t = arg_info(op->args[1])->val; @@ -1015,12 +1113,39 @@ static bool fold_count_zeros(OptContext *ctx, TCGOp *op) } return tcg_opt_gen_mov(ctx, op, op->args[0], op->args[2]); } + + switch (ctx->type) { + case TCG_TYPE_I32: + z_mask = 31; + break; + case TCG_TYPE_I64: + z_mask = 63; + break; + default: + g_assert_not_reached(); + } + ctx->z_mask = arg_info(op->args[2])->z_mask | z_mask; + return false; } static bool fold_ctpop(OptContext *ctx, TCGOp *op) { - return fold_const1(ctx, op); + if (fold_const1(ctx, op)) { + return true; + } + + switch (ctx->type) { + case TCG_TYPE_I32: + ctx->z_mask = 32 | 31; + break; + case TCG_TYPE_I64: + ctx->z_mask = 64 | 63; + break; + default: + g_assert_not_reached(); + } + return false; } static bool fold_deposit(OptContext *ctx, TCGOp *op) @@ -1032,6 +1157,10 @@ static bool fold_deposit(OptContext *ctx, TCGOp *op) t1 = deposit64(t1, op->args[3], op->args[4], t2); return tcg_opt_gen_movi(ctx, op, op->args[0], t1); } + + ctx->z_mask = deposit64(arg_info(op->args[1])->z_mask, + op->args[3], op->args[4], + arg_info(op->args[2])->z_mask); return false; } @@ -1077,6 +1206,8 @@ static bool fold_eqv(OptContext *ctx, TCGOp *op) static bool fold_extract(OptContext *ctx, TCGOp *op) { + uint64_t z_mask_old, z_mask; + if (arg_is_const(op->args[1])) { uint64_t t; @@ -1084,7 +1215,15 @@ static bool fold_extract(OptContext *ctx, TCGOp *op) t = extract64(t, op->args[2], op->args[3]); return tcg_opt_gen_movi(ctx, op, op->args[0], t); } - return false; + + z_mask_old = arg_info(op->args[1])->z_mask; + z_mask = extract64(z_mask_old, op->args[2], op->args[3]); + if (op->args[2] == 0) { + ctx->a_mask = z_mask_old ^ z_mask; + } + ctx->z_mask = z_mask; + + return fold_masks(ctx, op); } static bool fold_extract2(OptContext *ctx, TCGOp *op) @@ -1108,12 +1247,83 @@ static bool fold_extract2(OptContext *ctx, TCGOp *op) static bool fold_exts(OptContext *ctx, TCGOp *op) { - return fold_const1(ctx, op); + uint64_t z_mask_old, z_mask, sign; + bool type_change = false; + + if (fold_const1(ctx, op)) { + return true; + } + + z_mask_old = z_mask = arg_info(op->args[1])->z_mask; + + switch (op->opc) { + CASE_OP_32_64(ext8s): + sign = INT8_MIN; + z_mask = (uint8_t)z_mask; + break; + CASE_OP_32_64(ext16s): + sign = INT16_MIN; + z_mask = (uint16_t)z_mask; + break; + case INDEX_op_ext_i32_i64: + type_change = true; + QEMU_FALLTHROUGH; + case INDEX_op_ext32s_i64: + sign = INT32_MIN; + z_mask = (uint32_t)z_mask; + break; + default: + g_assert_not_reached(); + } + + if (z_mask & sign) { + z_mask |= sign; + } else if (!type_change) { + ctx->a_mask = z_mask_old ^ z_mask; + } + ctx->z_mask = z_mask; + + return fold_masks(ctx, op); } static bool fold_extu(OptContext *ctx, TCGOp *op) { - return fold_const1(ctx, op); + uint64_t z_mask_old, z_mask; + bool type_change = false; + + if (fold_const1(ctx, op)) { + return true; + } + + z_mask_old = z_mask = arg_info(op->args[1])->z_mask; + + switch (op->opc) { + CASE_OP_32_64(ext8u): + z_mask = (uint8_t)z_mask; + break; + CASE_OP_32_64(ext16u): + z_mask = (uint16_t)z_mask; + break; + case INDEX_op_extrl_i64_i32: + case INDEX_op_extu_i32_i64: + type_change = true; + QEMU_FALLTHROUGH; + case INDEX_op_ext32u_i64: + z_mask = (uint32_t)z_mask; + break; + case INDEX_op_extrh_i64_i32: + type_change = true; + z_mask >>= 32; + break; + default: + g_assert_not_reached(); + } + + ctx->z_mask = z_mask; + if (!type_change) { + ctx->a_mask = z_mask_old ^ z_mask; + } + return fold_masks(ctx, op); } static bool fold_mb(OptContext *ctx, TCGOp *op) @@ -1154,6 +1364,9 @@ static bool fold_movcond(OptContext *ctx, TCGOp *op) return tcg_opt_gen_mov(ctx, op, op->args[0], op->args[4 - i]); } + ctx->z_mask = arg_info(op->args[3])->z_mask + | arg_info(op->args[4])->z_mask; + if (arg_is_const(op->args[3]) && arg_is_const(op->args[4])) { uint64_t tv = arg_info(op->args[3])->val; uint64_t fv = arg_info(op->args[4])->val; @@ -1228,9 +1441,16 @@ static bool fold_nand(OptContext *ctx, TCGOp *op) static bool fold_neg(OptContext *ctx, TCGOp *op) { + uint64_t z_mask; + if (fold_const1(ctx, op)) { return true; } + + /* Set to 1 all bits to the left of the rightmost. */ + z_mask = arg_info(op->args[1])->z_mask; + ctx->z_mask = -(z_mask & -z_mask); + /* * Because of fold_sub_to_neg, we want to always return true, * via finish_folding. @@ -1266,7 +1486,10 @@ static bool fold_or(OptContext *ctx, TCGOp *op) fold_xx_to_x(ctx, op)) { return true; } - return false; + + ctx->z_mask = arg_info(op->args[1])->z_mask + | arg_info(op->args[2])->z_mask; + return fold_masks(ctx, op); } static bool fold_orc(OptContext *ctx, TCGOp *op) @@ -1281,6 +1504,15 @@ static bool fold_orc(OptContext *ctx, TCGOp *op) static bool fold_qemu_ld(OptContext *ctx, TCGOp *op) { + const TCGOpDef *def = &tcg_op_defs[op->opc]; + MemOpIdx oi = op->args[def->nb_oargs + def->nb_iargs]; + MemOp mop = get_memop(oi); + int width = 8 * memop_size(mop); + + if (!(mop & MO_SIGN) && width < 64) { + ctx->z_mask = MAKE_64BIT_MASK(0, width); + } + /* Opcodes that touch guest memory stop the mb optimization. */ ctx->prev_mb = NULL; return false; @@ -1306,6 +1538,8 @@ static bool fold_setcond(OptContext *ctx, TCGOp *op) if (i >= 0) { return tcg_opt_gen_movi(ctx, op, op->args[0], i); } + + ctx->z_mask = 1; return false; } @@ -1372,6 +1606,8 @@ static bool fold_setcond2(OptContext *ctx, TCGOp *op) op->opc = INDEX_op_setcond_i32; break; } + + ctx->z_mask = 1; return false; do_setcond_const: @@ -1380,6 +1616,8 @@ static bool fold_setcond2(OptContext *ctx, TCGOp *op) static bool fold_sextract(OptContext *ctx, TCGOp *op) { + int64_t z_mask_old, z_mask; + if (arg_is_const(op->args[1])) { uint64_t t; @@ -1387,7 +1625,15 @@ static bool fold_sextract(OptContext *ctx, TCGOp *op) t = sextract64(t, op->args[2], op->args[3]); return tcg_opt_gen_movi(ctx, op, op->args[0], t); } - return false; + + z_mask_old = arg_info(op->args[1])->z_mask; + z_mask = sextract64(z_mask_old, op->args[2], op->args[3]); + if (op->args[2] == 0 && z_mask >= 0) { + ctx->a_mask = z_mask_old ^ z_mask; + } + ctx->z_mask = z_mask; + + return fold_masks(ctx, op); } static bool fold_shift(OptContext *ctx, TCGOp *op) @@ -1397,6 +1643,13 @@ static bool fold_shift(OptContext *ctx, TCGOp *op) fold_xi_to_x(ctx, op, 0)) { return true; } + + if (arg_is_const(op->args[2])) { + ctx->z_mask = do_constant_folding(op->opc, ctx->type, + arg_info(op->args[1])->z_mask, + arg_info(op->args[2])->val); + return fold_masks(ctx, op); + } return false; } @@ -1452,6 +1705,25 @@ static bool fold_sub2_i32(OptContext *ctx, TCGOp *op) return fold_addsub2_i32(ctx, op, false); } +static bool fold_tcg_ld(OptContext *ctx, TCGOp *op) +{ + /* We can't do any folding with a load, but we can record bits. */ + switch (op->opc) { + CASE_OP_32_64(ld8u): + ctx->z_mask = MAKE_64BIT_MASK(0, 8); + break; + CASE_OP_32_64(ld16u): + ctx->z_mask = MAKE_64BIT_MASK(0, 16); + break; + case INDEX_op_ld32u_i64: + ctx->z_mask = MAKE_64BIT_MASK(0, 32); + break; + default: + g_assert_not_reached(); + } + return false; +} + static bool fold_xor(OptContext *ctx, TCGOp *op) { if (fold_const2(ctx, op) || @@ -1460,7 +1732,10 @@ static bool fold_xor(OptContext *ctx, TCGOp *op) fold_xi_to_not(ctx, op, -1)) { return true; } - return false; + + ctx->z_mask = arg_info(op->args[1])->z_mask + | arg_info(op->args[2])->z_mask; + return fold_masks(ctx, op); } /* Propagate constants and copies, fold constant expressions. */ @@ -1481,7 +1756,6 @@ void tcg_optimize(TCGContext *s) } QTAILQ_FOREACH_SAFE(op, &s->ops, link, op_next) { - uint64_t z_mask, partmask, affected, tmp; TCGOpcode opc = op->opc; const TCGOpDef *def; bool done = false; @@ -1562,245 +1836,9 @@ void tcg_optimize(TCGContext *s) break; } - /* Simplify using known-zero bits. Currently only ops with a single - output argument is supported. */ - z_mask = -1; - affected = -1; - switch (opc) { - CASE_OP_32_64(ext8s): - if ((arg_info(op->args[1])->z_mask & 0x80) != 0) { - break; - } - QEMU_FALLTHROUGH; - CASE_OP_32_64(ext8u): - z_mask = 0xff; - goto and_const; - CASE_OP_32_64(ext16s): - if ((arg_info(op->args[1])->z_mask & 0x8000) != 0) { - break; - } - QEMU_FALLTHROUGH; - CASE_OP_32_64(ext16u): - z_mask = 0xffff; - goto and_const; - case INDEX_op_ext32s_i64: - if ((arg_info(op->args[1])->z_mask & 0x80000000) != 0) { - break; - } - QEMU_FALLTHROUGH; - case INDEX_op_ext32u_i64: - z_mask = 0xffffffffU; - goto and_const; - - CASE_OP_32_64(and): - z_mask = arg_info(op->args[2])->z_mask; - if (arg_is_const(op->args[2])) { - and_const: - affected = arg_info(op->args[1])->z_mask & ~z_mask; - } - z_mask = arg_info(op->args[1])->z_mask & z_mask; - break; - - case INDEX_op_ext_i32_i64: - if ((arg_info(op->args[1])->z_mask & 0x80000000) != 0) { - break; - } - QEMU_FALLTHROUGH; - case INDEX_op_extu_i32_i64: - /* We do not compute affected as it is a size changing op. */ - z_mask = (uint32_t)arg_info(op->args[1])->z_mask; - break; - - CASE_OP_32_64(andc): - /* Known-zeros does not imply known-ones. Therefore unless - op->args[2] is constant, we can't infer anything from it. */ - if (arg_is_const(op->args[2])) { - z_mask = ~arg_info(op->args[2])->z_mask; - goto and_const; - } - /* But we certainly know nothing outside args[1] may be set. */ - z_mask = arg_info(op->args[1])->z_mask; - break; - - case INDEX_op_sar_i32: - if (arg_is_const(op->args[2])) { - tmp = arg_info(op->args[2])->val & 31; - z_mask = (int32_t)arg_info(op->args[1])->z_mask >> tmp; - } - break; - case INDEX_op_sar_i64: - if (arg_is_const(op->args[2])) { - tmp = arg_info(op->args[2])->val & 63; - z_mask = (int64_t)arg_info(op->args[1])->z_mask >> tmp; - } - break; - - case INDEX_op_shr_i32: - if (arg_is_const(op->args[2])) { - tmp = arg_info(op->args[2])->val & 31; - z_mask = (uint32_t)arg_info(op->args[1])->z_mask >> tmp; - } - break; - case INDEX_op_shr_i64: - if (arg_is_const(op->args[2])) { - tmp = arg_info(op->args[2])->val & 63; - z_mask = (uint64_t)arg_info(op->args[1])->z_mask >> tmp; - } - break; - - case INDEX_op_extrl_i64_i32: - z_mask = (uint32_t)arg_info(op->args[1])->z_mask; - break; - case INDEX_op_extrh_i64_i32: - z_mask = (uint64_t)arg_info(op->args[1])->z_mask >> 32; - break; - - CASE_OP_32_64(shl): - if (arg_is_const(op->args[2])) { - tmp = arg_info(op->args[2])->val & (TCG_TARGET_REG_BITS - 1); - z_mask = arg_info(op->args[1])->z_mask << tmp; - } - break; - - CASE_OP_32_64(neg): - /* Set to 1 all bits to the left of the rightmost. */ - z_mask = -(arg_info(op->args[1])->z_mask - & -arg_info(op->args[1])->z_mask); - break; - - CASE_OP_32_64(deposit): - z_mask = deposit64(arg_info(op->args[1])->z_mask, - op->args[3], op->args[4], - arg_info(op->args[2])->z_mask); - break; - - CASE_OP_32_64(extract): - z_mask = extract64(arg_info(op->args[1])->z_mask, - op->args[2], op->args[3]); - if (op->args[2] == 0) { - affected = arg_info(op->args[1])->z_mask & ~z_mask; - } - break; - CASE_OP_32_64(sextract): - z_mask = sextract64(arg_info(op->args[1])->z_mask, - op->args[2], op->args[3]); - if (op->args[2] == 0 && (tcg_target_long)z_mask >= 0) { - affected = arg_info(op->args[1])->z_mask & ~z_mask; - } - break; - - CASE_OP_32_64(or): - CASE_OP_32_64(xor): - z_mask = arg_info(op->args[1])->z_mask - | arg_info(op->args[2])->z_mask; - break; - - case INDEX_op_clz_i32: - case INDEX_op_ctz_i32: - z_mask = arg_info(op->args[2])->z_mask | 31; - break; - - case INDEX_op_clz_i64: - case INDEX_op_ctz_i64: - z_mask = arg_info(op->args[2])->z_mask | 63; - break; - - case INDEX_op_ctpop_i32: - z_mask = 32 | 31; - break; - case INDEX_op_ctpop_i64: - z_mask = 64 | 63; - break; - - CASE_OP_32_64(setcond): - case INDEX_op_setcond2_i32: - z_mask = 1; - break; - - CASE_OP_32_64(movcond): - z_mask = arg_info(op->args[3])->z_mask - | arg_info(op->args[4])->z_mask; - break; - - CASE_OP_32_64(ld8u): - z_mask = 0xff; - break; - CASE_OP_32_64(ld16u): - z_mask = 0xffff; - break; - case INDEX_op_ld32u_i64: - z_mask = 0xffffffffu; - break; - - CASE_OP_32_64(qemu_ld): - { - MemOpIdx oi = op->args[def->nb_oargs + def->nb_iargs]; - MemOp mop = get_memop(oi); - if (!(mop & MO_SIGN)) { - z_mask = (2ULL << ((8 << (mop & MO_SIZE)) - 1)) - 1; - } - } - break; - - CASE_OP_32_64(bswap16): - z_mask = arg_info(op->args[1])->z_mask; - if (z_mask <= 0xffff) { - op->args[2] |= TCG_BSWAP_IZ; - } - z_mask = bswap16(z_mask); - switch (op->args[2] & (TCG_BSWAP_OZ | TCG_BSWAP_OS)) { - case TCG_BSWAP_OZ: - break; - case TCG_BSWAP_OS: - z_mask = (int16_t)z_mask; - break; - default: /* undefined high bits */ - z_mask |= MAKE_64BIT_MASK(16, 48); - break; - } - break; - - case INDEX_op_bswap32_i64: - z_mask = arg_info(op->args[1])->z_mask; - if (z_mask <= 0xffffffffu) { - op->args[2] |= TCG_BSWAP_IZ; - } - z_mask = bswap32(z_mask); - switch (op->args[2] & (TCG_BSWAP_OZ | TCG_BSWAP_OS)) { - case TCG_BSWAP_OZ: - break; - case TCG_BSWAP_OS: - z_mask = (int32_t)z_mask; - break; - default: /* undefined high bits */ - z_mask |= MAKE_64BIT_MASK(32, 32); - break; - } - break; - - default: - break; - } - - /* 32-bit ops generate 32-bit results. For the result is zero test - below, we can ignore high bits, but for further optimizations we - need to record that the high bits contain garbage. */ - partmask = z_mask; - if (ctx.type == TCG_TYPE_I32) { - z_mask |= ~(tcg_target_ulong)0xffffffffu; - partmask &= 0xffffffffu; - affected &= 0xffffffffu; - } - ctx.z_mask = z_mask; - - if (partmask == 0) { - tcg_opt_gen_movi(&ctx, op, op->args[0], 0); - continue; - } - if (affected == 0) { - tcg_opt_gen_mov(&ctx, op, op->args[0], op->args[1]); - continue; - } + /* Assume all bits affected, and no bits known zero. */ + ctx.a_mask = -1; + ctx.z_mask = -1; /* * Process each opcode. @@ -1873,6 +1911,11 @@ void tcg_optimize(TCGContext *s) case INDEX_op_extrh_i64_i32: done = fold_extu(&ctx, op); break; + CASE_OP_32_64(ld8u): + CASE_OP_32_64(ld16u): + case INDEX_op_ld32u_i64: + done = fold_tcg_ld(&ctx, op); + break; case INDEX_op_mb: done = fold_mb(&ctx, op); break;