luau/CodeGen/src/OptimizeFinalX64.cpp

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// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
#include "Luau/OptimizeFinalX64.h"
#include "Luau/IrUtils.h"
#include <utility>
namespace Luau
{
namespace CodeGen
{
// x64 assembly allows memory operands, but IR separates loads from uses
// To improve final x64 lowering, we try to 'inline' single-use register/constant loads into some of our instructions
// This pass might not be useful on different architectures
static void optimizeMemoryOperandsX64(IrFunction& function, IrBlock& block)
{
LUAU_ASSERT(block.kind != IrBlockKind::Dead);
for (uint32_t index = block.start; true; index++)
{
LUAU_ASSERT(index < function.instructions.size());
IrInst& inst = function.instructions[index];
switch (inst.cmd)
{
case IrCmd::CHECK_TAG:
{
if (inst.a.kind == IrOpKind::Inst)
{
IrInst& tag = function.instOp(inst.a);
if (tag.useCount == 1 && tag.cmd == IrCmd::LOAD_TAG && (tag.a.kind == IrOpKind::VmReg || tag.a.kind == IrOpKind::VmConst))
replace(function, inst.a, tag.a);
}
break;
}
case IrCmd::ADD_NUM:
case IrCmd::SUB_NUM:
case IrCmd::MUL_NUM:
case IrCmd::DIV_NUM:
case IrCmd::MOD_NUM:
case IrCmd::POW_NUM:
{
if (inst.b.kind == IrOpKind::Inst)
{
IrInst& rhs = function.instOp(inst.b);
if (rhs.useCount == 1 && rhs.cmd == IrCmd::LOAD_DOUBLE && (rhs.a.kind == IrOpKind::VmReg || rhs.a.kind == IrOpKind::VmConst))
replace(function, inst.b, rhs.a);
}
break;
}
case IrCmd::JUMP_EQ_TAG:
{
if (inst.a.kind == IrOpKind::Inst)
{
IrInst& tagA = function.instOp(inst.a);
if (tagA.useCount == 1 && tagA.cmd == IrCmd::LOAD_TAG && (tagA.a.kind == IrOpKind::VmReg || tagA.a.kind == IrOpKind::VmConst))
{
replace(function, inst.a, tagA.a);
break;
}
}
if (inst.b.kind == IrOpKind::Inst)
{
IrInst& tagB = function.instOp(inst.b);
if (tagB.useCount == 1 && tagB.cmd == IrCmd::LOAD_TAG && (tagB.a.kind == IrOpKind::VmReg || tagB.a.kind == IrOpKind::VmConst))
{
std::swap(inst.a, inst.b);
replace(function, inst.a, tagB.a);
}
}
break;
}
case IrCmd::JUMP_CMP_NUM:
{
if (inst.a.kind == IrOpKind::Inst)
{
IrInst& num = function.instOp(inst.a);
if (num.useCount == 1 && num.cmd == IrCmd::LOAD_DOUBLE)
replace(function, inst.a, num.a);
}
break;
}
default:
break;
}
if (isBlockTerminator(inst.cmd))
break;
}
}
void optimizeMemoryOperandsX64(IrFunction& function)
{
for (IrBlock& block : function.blocks)
{
if (block.kind == IrBlockKind::Dead)
continue;
optimizeMemoryOperandsX64(function, block);
}
}
} // namespace CodeGen
} // namespace Luau