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/*
* %CopyrightBegin%
*
* Copyright Ericsson AB 2020-2020. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* %CopyrightEnd%
*/
#include <algorithm>
#include "beam_asm.hpp"
using namespace asmjit;
void BeamModuleAssembler::emit_linear_search(x86::Gp comparand,
const ArgVal &Fail,
const std::vector<ArgVal> &args) {
int count = args.size() / 2;
for (int i = 0; i < count; i++) {
const ArgVal &value = args[i];
const ArgVal &label = args[i + count];
cmp_arg(comparand, value, ARG1);
a.je(labels[label.getValue()]);
}
if (Fail.getType() == ArgVal::f) {
a.jmp(labels[Fail.getValue()]);
} else {
/* NIL means fallthrough to the next instruction. */
ASSERT(Fail.getType() == ArgVal::i && Fail.getValue() == NIL);
}
}
void BeamModuleAssembler::emit_i_select_tuple_arity(
const ArgVal &Src,
const ArgVal &Fail,
const ArgVal &Size,
const std::vector<ArgVal> &args) {
mov_arg(ARG2, Src);
emit_is_boxed(labels[Fail.getValue()], ARG2);
x86::Gp boxed_ptr = emit_ptr_val(ARG2, ARG2);
ERTS_CT_ASSERT(Support::isInt32(make_arityval(MAX_ARITYVAL)));
a.mov(ARG2d, emit_boxed_val(boxed_ptr, 0, sizeof(Uint32)));
ERTS_CT_ASSERT(_TAG_HEADER_ARITYVAL == 0);
a.test(ARG2.r8(), imm(_TAG_HEADER_MASK));
a.jne(labels[Fail.getValue()]);
ERTS_CT_ASSERT(Support::isInt32(make_arityval(MAX_ARITYVAL)));
int count = args.size() / 2;
for (int i = 0; i < count; i++) {
const ArgVal &value = args[i];
const ArgVal &label = args[i + count];
a.cmp(ARG2d, imm(value.getValue()));
a.je(labels[label.getValue()]);
}
a.jne(labels[Fail.getValue()]);
}
void BeamModuleAssembler::emit_i_select_val_lins(
const ArgVal &Src,
const ArgVal &Fail,
const ArgVal &Size,
const std::vector<ArgVal> &args) {
ASSERT(Size.getValue() == args.size());
mov_arg(ARG2, Src);
if (emit_optimized_three_way_select(Fail, args))
return;
emit_linear_search(ARG2, Fail, args);
}
void BeamModuleAssembler::emit_i_select_val_bins(
const ArgVal &Src,
const ArgVal &Fail,
const ArgVal &Size,
const std::vector<ArgVal> &args) {
ASSERT(Size.getValue() == args.size());
int count = args.size() / 2;
Label fail;
if (Fail.getType() == ArgVal::f) {
fail = labels[Fail.getValue()];
} else {
/* NIL means fallthrough to the next instruction. */
ASSERT(Fail.getType() == ArgVal::i && Fail.getValue() == NIL);
fail = a.newLabel();
}
mov_arg(ARG2, Src);
comment("Binary search in table of %lu elements", count);
emit_binsearch_nodes(0, count - 1, Fail, args);
if (Fail.getType() == ArgVal::i) {
a.bind(fail);
}
}
/*
* Emit code for a binary search through an interval Left <= Right of
* the i_select_val argument vector `args`.
*
* ARG2 is the value being looked up.
*/
void BeamModuleAssembler::emit_binsearch_nodes(
size_t Left,
size_t Right,
const ArgVal &Fail,
const std::vector<ArgVal> &args) {
ASSERT(Left <= Right);
ASSERT(Right < args.size() / 2);
size_t mid = (Left + Right) >> 1;
ArgVal midval(ArgVal::i, args[mid].getValue());
int count = args.size() / 2;
size_t remaining = (Right - Left + 1);
if (remaining <= 10) {
/* Measurements on randomly generated select_val instructions
have shown that linear search is faster than binary search
when there are ten or less elements.
*/
std::vector<ArgVal> shrunk;
comment("Linear search in [%lu..%lu], %lu elements",
Left,
Right,
remaining);
shrunk.reserve(remaining * 2);
shrunk.insert(shrunk.end(),
args.begin() + Left,
args.begin() + Left + remaining);
shrunk.insert(shrunk.end(),
args.begin() + Left + count,
args.begin() + count + Left + remaining);
if (!emit_optimized_three_way_select(Fail, shrunk))
emit_linear_search(ARG2, Fail, shrunk);
return;
}
comment("Subtree [%lu..%lu], pivot %lu", Left, Right, mid);
cmp_arg(ARG2, midval, ARG1);
if (Left == Right) {
a.je(labels[args[mid + count].getValue()]);
a.jmp(labels[Fail.getValue()]);
return;
}
a.je(labels[args[mid + count].getValue()]);
if (Left == mid) {
a.jb(labels[Fail.getValue()]);
} else {
Label right_tree = a.newLabel();
a.ja(right_tree);
emit_binsearch_nodes(Left, mid - 1, Fail, args);
a.bind(right_tree);
}
emit_binsearch_nodes(mid + 1, Right, Fail, args);
}
void BeamModuleAssembler::emit_i_jump_on_val(const ArgVal &Src,
const ArgVal &Fail,
const ArgVal &Base,
const ArgVal &Size,
const std::vector<ArgVal> &args) {
Label data = embed_vararg_rodata(args, 0);
Label fail;
ASSERT(Size.getValue() == args.size());
mov_arg(ARG1, Src);
a.mov(RETd, ARG1d);
a.and_(RETb, imm(_TAG_IMMED1_MASK));
a.cmp(RETb, imm(_TAG_IMMED1_SMALL));
if (Fail.getType() == ArgVal::f) {
a.jne(labels[Fail.getValue()]);
} else {
/* NIL means fallthrough to the next instruction. */
ASSERT(Fail.getType() == ArgVal::i && Fail.getValue() == NIL);
fail = a.newLabel();
a.short_().jne(fail);
}
a.sar(ARG1, imm(_TAG_IMMED1_SIZE));
if (Base.getValue() != 0) {
if (Support::isInt32((Sint)Base.getValue())) {
a.sub(ARG1, imm(Base.getValue()));
} else {
a.mov(ARG2, imm(Base.getValue()));
a.sub(ARG1, ARG2);
}
}
a.cmp(ARG1, imm(args.size()));
if (Fail.getType() == ArgVal::f) {
a.jae(labels[Fail.getValue()]);
} else {
a.short_().jae(fail);
}
a.lea(RET, x86::qword_ptr(data));
a.jmp(x86::qword_ptr(RET, ARG1, 3));
if (Fail.getType() == ArgVal::i) {
a.bind(fail);
}
}
/*
* Attempt to optimize the case when a select_val has exactly two
* values which only differ by one bit and they both branch to the
* same label.
*
* The optimization makes use of the observation that (V == X || V ==
* Y) is equivalent to (V | (X ^ Y)) == (X | Y) when (X ^ Y) has only
* one bit set.
*
* ARG2 contains the value.
* Return true if the optimization was possible, in
* which case ARG1 should be considered trashed.
*/
bool BeamModuleAssembler::emit_optimized_three_way_select(
const ArgVal &Fail,
const std::vector<ArgVal> &args) {
if (args.size() != 4 || (args[2].getValue() != args[3].getValue()))
return false;
uint64_t x = args[0].getValue();
uint64_t y = args[1].getValue();
uint64_t combined = x | y;
uint64_t diff = x ^ y;
ArgVal val(ArgVal::i, combined);
if ((diff & (diff - 1)) != 0)
return false;
comment("(Src == 0x%x || Src == 0x%x) <=> (Src | 0x%x) == 0x%x",
x,
y,
diff,
combined);
if (Support::isInt32((Sint)diff)) {
a.or_(ARG2, imm(diff));
} else {
a.mov(ARG1, imm(diff));
a.or_(ARG2, ARG1);
}
cmp_arg(ARG2, val, ARG1);
a.je(labels[args[2].getValue()]);
if (Fail.getType() == ArgVal::f) {
a.jmp(labels[Fail.getValue()]);
} else {
/* NIL means fallthrough to the next instruction. */
ASSERT(Fail.getType() == ArgVal::i && Fail.getValue() == NIL);
}
return true;
}
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