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GCC fails to optimize division/mod by 8 into bitshift/mask.

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This commit is contained in:
Ken MacKay
2014-05-17 17:32:30 -07:00
parent d172e28c85
commit 58610ddcec
1 changed files with 13 additions and 5 deletions
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uECC.c
+13 -5
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@@ -79,6 +79,9 @@ typedef int16_t bitcount_t;
typedef int8_t cmpresult_t;
#define HIGH_BIT_SET 0x80
#define uECC_WORD_BITS 8
#define uECC_WORD_BITS_SHIFT 3
#define uECC_WORD_BITS_MASK 0x07
#define uECC_WORDS_1 20
#define uECC_WORDS_2 24
@@ -181,6 +184,9 @@ typedef int bitcount_t;
typedef int cmpresult_t;
#define HIGH_BIT_SET 0x80000000
#define uECC_WORD_BITS 32
#define uECC_WORD_BITS_SHIFT 5
#define uECC_WORD_BITS_MASK 0x01F
#define uECC_WORDS_1 5
#define uECC_WORDS_2 6
@@ -235,6 +241,9 @@ typedef int bitcount_t;
typedef int cmpresult_t;
#define HIGH_BIT_SET 0x8000000000000000ull
#define uECC_WORD_BITS 64
#define uECC_WORD_BITS_SHIFT 6
#define uECC_WORD_BITS_MASK 0x03F
#define uECC_WORDS_1 3
#define uECC_WORDS_2 3
@@ -277,9 +286,8 @@ typedef int cmpresult_t;
#define Curve_N_3 {0xF3B9CAC2FC632551ull, 0xBCE6FAADA7179E84ull, 0xFFFFFFFFFFFFFFFFull, 0xFFFFFFFF00000000ull}
#define Curve_N_4 {0xBFD25E8CD0364141, 0xBAAEDCE6AF48A03B, 0xFFFFFFFFFFFFFFFE, 0xFFFFFFFFFFFFFFFF}
#endif
#endif /* (uECC_WORD_SIZE == 8) */
#define uECC_WORD_BITS (uECC_WORD_SIZE * 8)
#define uECC_WORDS uECC_CONCAT(uECC_WORDS_, uECC_CURVE)
#define uECC_N_WORDS uECC_CONCAT(uECC_N_WORDS_, uECC_CURVE)
@@ -434,7 +442,7 @@ static uECC_word_t vli_isZero(const uECC_word_t *p_vli)
#if !asm_testBit
static uECC_word_t vli_testBit(const uECC_word_t *p_vli, bitcount_t p_bit)
{
return (p_vli[p_bit/uECC_WORD_BITS] & ((uECC_word_t)1 << (p_bit % uECC_WORD_BITS)));
return (p_vli[p_bit >> uECC_WORD_BITS_SHIFT] & ((uECC_word_t)1 << (p_bit & uECC_WORD_BITS_MASK)));
}
#endif
@@ -470,7 +478,7 @@ static bitcount_t vli_numBits(const uECC_word_t *p_vli, wordcount_t p_maxWords)
l_digit >>= 1;
}
return ((bitcount_t)(l_numDigits - 1) * uECC_WORD_BITS + i);
return (((bitcount_t)(l_numDigits - 1) << uECC_WORD_BITS_SHIFT) + i);
}
#endif /* !asm_numBits */
@@ -2074,7 +2082,7 @@ static void vli_modMult_n(uECC_word_t *p_result, uECC_word_t *p_left, uECC_word_
bitcount_t i;
uECC_word_t l_index = 1;
for(i=0; i<=((uECC_N_WORDS * uECC_WORD_BITS) + (uECC_WORD_BITS - 1)); ++i)
for(i=0; i<=((((bitcount_t)uECC_N_WORDS) << uECC_WORD_BITS_SHIFT) + (uECC_WORD_BITS - 1)); ++i)
{
uECC_word_t l_borrow = vli2_sub_n(v[1-l_index], v[l_index], l_modMultiple);
l_index = !(l_index ^ l_borrow); /* Swap the index if there was no borrow */