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Swap mg and eg in internal representation of Score

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Instrumentation shows that in make_score(mg, eg) calls, the mg value is
zero in 25,9% of the calls while the eg value is zero in 36,8% of the
calls.

Swapping the internal fields of mg and eg in the internal
representation of Score allows the compiler to optimize away the shift
in (eg << 16) + mg in more cases, thus resulting in a 0.3% speed-up
overall.

No functional change
This commit is contained in:
Stéphane Nicolet 2016-09-16 18:18:53 +02:00 • committed by Marco Costalba
parent 057d710fc2
commit ea41f18e6e
1 changed files with 8 additions and 8 deletions
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16
src/types.h
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@ -265,24 +265,24 @@ enum Rank {
enum Score : int { SCORE_ZERO };
inline Score make_score(int mg, int eg) {
return Score((mg << 16) + eg);
return Score((eg << 16) + mg);
}
/// Extracting the signed lower and upper 16 bits is not so trivial because
/// according to the standard a simple cast to short is implementation defined
/// and so is a right shift of a signed integer.
inline Value mg_value(Score s) {
union { uint16_t u; int16_t s; } mg = { uint16_t(unsigned(s + 0x8000) >> 16) };
return Value(mg.s);
}
inline Value eg_value(Score s) {
union { uint16_t u; int16_t s; } eg = { uint16_t(unsigned(s)) };
union { uint16_t u; int16_t s; } eg = { uint16_t(unsigned(s + 0x8000) >> 16) };
return Value(eg.s);
}
inline Value mg_value(Score s) {
union { uint16_t u; int16_t s; } mg = { uint16_t(unsigned(s)) };
return Value(mg.s);
}
#define ENABLE_BASE_OPERATORS_ON(T) \
inline T operator+(T d1, T d2) { return T(int(d1) + int(d2)); } \
inline T operator-(T d1, T d2) { return T(int(d1) - int(d2)); } \