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AP_Math: add alternate implementation of parity for AP_Periph 

the __builtin_parity methods hardfault on AP_Periph builds
This commit is contained in:
Peter Barker 2023-06-06 13:54:48 +10:00 committed by Peter Barker
parent 109e29f048
commit c463b0d154
2 changed files with 37 additions and 1 deletions
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26
libraries/AP_Math/crc.cpp
View File

@ -19,6 +19,8 @@
#include <stdint.h>
#include "crc.h"
#include <AP_HAL/AP_HAL_Boards.h>
/**
* crc4 method from datasheet for 16 bytes (8 short values)
*
@ -540,7 +542,29 @@ uint64_t crc_crc64(const uint32_t *data, uint16_t num_words)
return crc;
}
// return the parity of byte - "1" if there is an odd number of bits
// set, "0" if there is an even number of bits set note that
// __builtin_parity causes hardfaults on Pixracer-periph - and is
// slower on 1 byte than this:
uint8_t parity(uint8_t byte)
{
return __builtin_parity(byte);
uint8_t p = 0;
p ^= byte & 0x1;
byte >>= 1;
p ^= byte & 0x1;
byte >>= 1;
p ^= byte & 0x1;
byte >>= 1;
p ^= byte & 0x1;
byte >>= 1;
p ^= byte & 0x1;
byte >>= 1;
p ^= byte & 0x1;
byte >>= 1;
p ^= byte & 0x1;
byte >>= 1;
p ^= byte & 0x1;
return p;
}

12
libraries/AP_Math/tests/test_math.cpp
View File

@ -680,6 +680,18 @@ TEST(MathTest, FIXEDWINGTURNRATE)
EXPECT_NEAR(56.187965393066406f, fixedwing_turn_rate(45, 10.0f), accuracy);
}
TEST(CRCTest, parity)
{
EXPECT_EQ(parity(0b1), 1);
EXPECT_EQ(parity(0b10), 1);
EXPECT_EQ(parity(0b100), 1);
EXPECT_EQ(parity(0b11), 0);
EXPECT_EQ(parity(0b110), 0);
EXPECT_EQ(parity(0b111), 1);
EXPECT_EQ(parity(0b11111111), 0);
}
AP_GTEST_PANIC()
AP_GTEST_MAIN()