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Ensure safety of ctz_debruijn implementation. #1194

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merged 1 commit into from
Jan 18, 2023
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Ensure safety of ctz_debruijn implementation. #1194

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4 changes: 2 additions & 2 deletions src/util.h
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Original file line number Diff line number Diff line change
Expand Up @@ -251,7 +251,7 @@ static SECP256K1_INLINE int secp256k1_ctz32_var_debruijn(uint32_t x) {
0x10, 0x07, 0x0C, 0x1A, 0x1F, 0x17, 0x12, 0x05, 0x15, 0x09, 0x0F, 0x0B,
0x1E, 0x11, 0x08, 0x0E, 0x1D, 0x0D, 0x1C, 0x1B
};
return debruijn[((x & -x) * 0x04D7651F) >> 27];
return debruijn[(uint32_t)((x & -x) * 0x04D7651FU) >> 27];
}

/* Determine the number of trailing zero bits in a (non-zero) 64-bit x.
Expand All @@ -264,7 +264,7 @@ static SECP256K1_INLINE int secp256k1_ctz64_var_debruijn(uint64_t x) {
63, 52, 6, 26, 37, 40, 33, 47, 61, 45, 43, 21, 23, 58, 17, 10,
51, 25, 36, 32, 60, 20, 57, 16, 50, 31, 19, 15, 30, 14, 13, 12
};
return debruijn[((x & -x) * 0x022FDD63CC95386D) >> 58];
return debruijn[(uint64_t)((x & -x) * 0x022FDD63CC95386DU) >> 58];
}

/* Determine the number of trailing zero bits in a (non-zero) 32-bit x. */
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