v3s16_optimization.cpp

v3s16_optimization.cpp

#include <iostream>
#include <stdint.h>
#include <vector>
#include "vector3d.h"

using u8 = unsigned char;
using s16 = int16_t;
using u16 = uint16_t;

using v3s16 = irr::core::vector3d<s16>;

struct MapNode
{
	u16 param0 = 1;
	u8 param1 = 2;
	u8 param2 = 3;
};

struct MapBlock {
	MapBlock()
	{
        	data.resize(zstride * ystride * 2);
	}

	inline MapNode getNodeNoCheck(s16 x, s16 y, s16 z)
	{
		return data[z * zstride + y * ystride + x];
	}

	//inline MapNode getNodeNoCheck(const v3s16 &p)
	inline MapNode getNodeNoCheck(v3s16 p)
	{
		return getNodeNoCheck(p.X, p.Y, p.Z);
	}

	std::vector<MapNode> data;
	u8 zstride = 2;
	u8 ystride = 2;
};

int main()
{
	MapBlock block;
	v3s16 pos;
	std::cin >> pos.X >> pos.Y >> pos.Z;
	MapNode n = block.getNodeNoCheck(pos);
	std::cout << (int)n.param0 << (int)n.param1 << (int)n.param2 << std::endl;
	return 0;
}

#if 0
/* v3s16 copying */

main:
	undefined4 local_4e;    <-- v3s16 X & Y
	short local_4a;         <-- v3s16 Z
	MapBlock local_48 [40]; <-- 40 bytes total (display issue)

	uVar1 = MapBlock::getNodeNoCheck(local_48,local_4e);
	^ Stack moved to RSI (2nd argument) using 2x OR, 2x SHL and some moves

getNodeNoCheck:
	short in_register_00000034;
	short local_18;
	short sStack22;
  
	sStack22 = (short)(param_1 >> 0x10);
	local_18 = (short)param_1;
	getNodeNoCheck(this,local_18,sStack22,in_register_00000034);
	return;

/* Const reference to v3s16 */

main:
	uVar1 = MapBlock::getNodeNoCheck(local_48,(vector3d *)&local_4e);
	^ single LEA command to retrieve the stack's address to pass directly

getNodeNoCheck:
	getNodeNoCheck(this,*(short *)param_1,*(short *)(param_1 + 2),*(short *)(param_1 + 4));
	^ looks shorter but has a few MOV operations more than the copying version
	return;
#endif