Title : Stockfish 16120309 - new version
link : Stockfish 16120309 - new version
Stockfish 16120309 - new version
Stockfish, UCI chess engine
Leader of the ranking list JCER = 3368
🔬 Author: Andrey Neporada
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Timestamp: 1480754227
Help GCC to optimize msb() to single instruction
GCC compiles builtin_clzll to “63 ^ BSR”. BSR is processor instruction "Bit Scan Reverse".
So old msb() function is basically 63 - 63 ^ BSR.
Unfortunately, GCC fails to simplify this expression.
Old function compiles to
bsrq %rdi, %rdi
movl $63, %eax
xorq $63, %rdi
subl %edi, %eax
ret
New function compiles to
bsrq %rdi, %rax
ret
BTW, Clang compiles both function to the same (optimal) code.
No functional change.
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Stockfish 16120309 - new version
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