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constant_pool: Use unordered_map rather than map

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`map` is an ordinal structure with log(n) time searches.
`unordered_map` uses O(1) average-time searches and O(n) in the worst
case where a bucket has a to a colliding hash and has to start chaining.
The unordered version should speed up our general-case when looking up
constants.

I've added a trivial order-dependent(_(0,1) and (1,0) will return a
different hash_) hash to combine a 128-bit constant into a
64-bit hash that generally will not collide, using a bit-rotate to
preserve entropy.
This commit is contained in:
Wunkolo 2021-12-23 12:37:58 -08:00 committed by merry
parent 28714ee75a
commit befc22a61e
1 changed files with 9 additions and 2 deletions
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11
src/dynarmic/backend/x64/constant_pool.h
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@ -5,8 +5,9 @@
#pragma once
#include <map>
#include <bit>
#include <tuple>
#include <unordered_map>
#include <xbyak/xbyak.h>
@ -29,7 +30,13 @@ public:
private:
static constexpr size_t align_size = 16; // bytes
std::map<std::tuple<u64, u64>, void*> constant_info;
struct ConstantHash {
std::size_t operator()(const std::tuple<u64, u64>& constant) const {
return std::get<0>(constant) ^ std::rotl<u64>(std::get<1>(constant), 1);
}
};
std::unordered_map<std::tuple<u64, u64>, void*, ConstantHash> constant_info;
BlockOfCode& code;
size_t pool_size;