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/*
* Copyright (C) 2015 The Android Open Source Project
*
* 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.
*/
#include "code_generator_utils.h"
#include <android-base/logging.h>
#include "nodes.h"
namespace art {
void CalculateMagicAndShiftForDivRem(int64_t divisor, bool is_long,
int64_t* magic, int* shift) {
// It does not make sense to calculate magic and shift for zero divisor.
DCHECK_NE(divisor, 0);
/* Implementation according to H.S.Warren's "Hacker's Delight" (Addison Wesley, 2002)
* Chapter 10 and T.Grablund, P.L.Montogomery's "Division by Invariant Integers Using
* Multiplication" (PLDI 1994).
* The magic number M and shift S can be calculated in the following way:
* Let nc be the most positive value of numerator(n) such that nc = kd - 1,
* where divisor(d) >= 2.
* Let nc be the most negative value of numerator(n) such that nc = kd + 1,
* where divisor(d) <= -2.
* Thus nc can be calculated like:
* nc = exp + exp % d - 1, where d >= 2 and exp = 2^31 for int or 2^63 for long
* nc = -exp + (exp + 1) % d, where d >= 2 and exp = 2^31 for int or 2^63 for long
*
* So the shift p is the smallest p satisfying
* 2^p > nc * (d - 2^p % d), where d >= 2
* 2^p > nc * (d + 2^p % d), where d <= -2.
*
* The magic number M is calculated by
* M = (2^p + d - 2^p % d) / d, where d >= 2
* M = (2^p - d - 2^p % d) / d, where d <= -2.
*
* Notice that p is always bigger than or equal to 32 (resp. 64), so we just return 32 - p
* (resp. 64 - p) as the shift number S.
*/
int64_t p = is_long ? 63 : 31;
const uint64_t exp = is_long ? (UINT64_C(1) << 63) : (UINT32_C(1) << 31);
// Initialize the computations.
uint64_t abs_d = (divisor >= 0) ? divisor : -divisor;
uint64_t sign_bit = is_long ? static_cast<uint64_t>(divisor) >> 63 :
static_cast<uint32_t>(divisor) >> 31;
uint64_t tmp = exp + sign_bit;
uint64_t abs_nc = tmp - 1 - (tmp % abs_d);
uint64_t quotient1 = exp / abs_nc;
uint64_t remainder1 = exp % abs_nc;
uint64_t quotient2 = exp / abs_d;
uint64_t remainder2 = exp % abs_d;
/*
* To avoid handling both positive and negative divisor, "Hacker's Delight"
* introduces a method to handle these 2 cases together to avoid duplication.
*/
uint64_t delta;
do {
p++;
quotient1 = 2 * quotient1;
remainder1 = 2 * remainder1;
if (remainder1 >= abs_nc) {
quotient1++;
remainder1 = remainder1 - abs_nc;
}
quotient2 = 2 * quotient2;
remainder2 = 2 * remainder2;
if (remainder2 >= abs_d) {
quotient2++;
remainder2 = remainder2 - abs_d;
}
delta = abs_d - remainder2;
} while (quotient1 < delta || (quotient1 == delta && remainder1 == 0));
*magic = (divisor > 0) ? (quotient2 + 1) : (-quotient2 - 1);
if (!is_long) {
*magic = static_cast<int>(*magic);
}
*shift = is_long ? p - 64 : p - 32;
}
bool IsBooleanValueOrMaterializedCondition(HInstruction* cond_input) {
return !cond_input->IsCondition() || !cond_input->IsEmittedAtUseSite();
}
} // namespace art