Ryujinx/ARMeilleure/CodeGen/Arm64/Arm64Optimizer.cs

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using ARMeilleure.CodeGen.Optimizations;
using ARMeilleure.IntermediateRepresentation;
using ARMeilleure.Translation;
using System.Collections.Generic;
using static ARMeilleure.IntermediateRepresentation.Operand.Factory;
using static ARMeilleure.IntermediateRepresentation.Operation.Factory;
namespace ARMeilleure.CodeGen.Arm64
{
static class Arm64Optimizer
{
private const int MaxConstantUses = 10000;
public static void RunPass(ControlFlowGraph cfg)
{
var constants = new Dictionary<ulong, Operand>();
Operand GetConstantCopy(BasicBlock block, Operation operation, Operand source)
{
// If the constant has many uses, we also force a new constant mov to be added, in order
// to avoid overflow of the counts field (that is limited to 16 bits).
if (!constants.TryGetValue(source.Value, out var constant) || constant.UsesCount > MaxConstantUses)
{
constant = Local(source.Type);
Operation copyOp = Operation(Instruction.Copy, constant, source);
block.Operations.AddBefore(operation, copyOp);
constants[source.Value] = constant;
}
return constant;
}
for (BasicBlock block = cfg.Blocks.First; block != null; block = block.ListNext)
{
constants.Clear();
Operation nextNode;
for (Operation node = block.Operations.First; node != default; node = nextNode)
{
nextNode = node.ListNext;
// Insert copies for constants that can't fit on a 32-bit immediate.
// Doing this early unblocks a few optimizations.
if (node.Instruction == Instruction.Add)
{
Operand src1 = node.GetSource(0);
Operand src2 = node.GetSource(1);
if (src1.Kind == OperandKind.Constant && (src1.Relocatable || ConstTooLong(src1, OperandType.I32)))
{
node.SetSource(0, GetConstantCopy(block, node, src1));
}
if (src2.Kind == OperandKind.Constant && (src2.Relocatable || ConstTooLong(src2, OperandType.I32)))
{
node.SetSource(1, GetConstantCopy(block, node, src2));
}
}
// Try to fold something like:
// lsl x1, x1, #2
// add x0, x0, x1
// ldr x0, [x0]
// add x2, x2, #16
// ldr x2, [x2]
// Into:
// ldr x0, [x0, x1, lsl #2]
// ldr x2, [x2, #16]
if (IsMemoryLoadOrStore(node.Instruction))
{
OperandType type;
if (node.Destination != default)
{
type = node.Destination.Type;
}
else
{
type = node.GetSource(1).Type;
}
Operand memOp = GetMemoryOperandOrNull(node.GetSource(0), type);
if (memOp != default)
{
node.SetSource(0, memOp);
}
}
}
}
Optimizer.RemoveUnusedNodes(cfg);
}
private static Operand GetMemoryOperandOrNull(Operand addr, OperandType type)
{
Operand baseOp = addr;
// First we check if the address is the result of a local X with immediate
// addition. If that is the case, then the baseOp is X, and the memory operand immediate
// becomes the addition immediate. Otherwise baseOp keeps being the address.
int imm = GetConstOp(ref baseOp, type);
if (imm != 0)
{
return MemoryOp(type, baseOp, default, Multiplier.x1, imm);
}
// Now we check if the baseOp is the result of a local Y with a local Z addition.
// If that is the case, we now set baseOp to Y and indexOp to Z. We further check
// if Z is the result of a left shift of local W by a value == 0 or == Log2(AccessSize),
// if that is the case, we set indexOp to W and adjust the scale value of the memory operand
// to match that of the left shift.
// There is one missed case, which is the address being a shift result, but this is
// probably not worth optimizing as it should never happen.
(Operand indexOp, Multiplier scale) = GetIndexOp(ref baseOp, type);
// If baseOp is still equal to address, then there's nothing that can be optimized.
if (baseOp == addr)
{
return default;
}
return MemoryOp(type, baseOp, indexOp, scale, 0);
}
private static int GetConstOp(ref Operand baseOp, OperandType accessType)
{
Operation operation = GetAsgOpWithInst(baseOp, Instruction.Add);
if (operation == default)
{
return 0;
}
Operand src1 = operation.GetSource(0);
Operand src2 = operation.GetSource(1);
Operand constOp;
Operand otherOp;
if (src1.Kind == OperandKind.Constant && src2.Kind == OperandKind.LocalVariable)
{
constOp = src1;
otherOp = src2;
}
else if (src1.Kind == OperandKind.LocalVariable && src2.Kind == OperandKind.Constant)
{
constOp = src2;
otherOp = src1;
}
else
{
return 0;
}
// If we have addition by a constant that we can't encode on the instruction,
// then we can't optimize it further.
if (ConstTooLong(constOp, accessType))
{
return 0;
}
baseOp = otherOp;
return constOp.AsInt32();
}
private static (Operand, Multiplier) GetIndexOp(ref Operand baseOp, OperandType accessType)
{
Operand indexOp = default;
Multiplier scale = Multiplier.x1;
Operation addOp = GetAsgOpWithInst(baseOp, Instruction.Add);
if (addOp == default)
{
return (indexOp, scale);
}
Operand src1 = addOp.GetSource(0);
Operand src2 = addOp.GetSource(1);
if (src1.Kind != OperandKind.LocalVariable || src2.Kind != OperandKind.LocalVariable)
{
return (indexOp, scale);
}
baseOp = src1;
indexOp = src2;
Operation shlOp = GetAsgOpWithInst(src1, Instruction.ShiftLeft);
bool indexOnSrc2 = false;
if (shlOp == default)
{
shlOp = GetAsgOpWithInst(src2, Instruction.ShiftLeft);
indexOnSrc2 = true;
}
if (shlOp != default)
{
Operand shSrc = shlOp.GetSource(0);
Operand shift = shlOp.GetSource(1);
int maxShift = Assembler.GetScaleForType(accessType);
if (shSrc.Kind == OperandKind.LocalVariable &&
shift.Kind == OperandKind.Constant &&
(shift.Value == 0 || shift.Value == (ulong)maxShift))
{
scale = shift.Value switch
{
1 => Multiplier.x2,
2 => Multiplier.x4,
3 => Multiplier.x8,
4 => Multiplier.x16,
_ => Multiplier.x1
};
baseOp = indexOnSrc2 ? src1 : src2;
indexOp = shSrc;
}
}
return (indexOp, scale);
}
private static Operation GetAsgOpWithInst(Operand op, Instruction inst)
{
// If we have multiple assignments, folding is not safe
// as the value may be different depending on the
// control flow path.
if (op.AssignmentsCount != 1)
{
return default;
}
Operation asgOp = op.Assignments[0];
if (asgOp.Instruction != inst)
{
return default;
}
return asgOp;
}
private static bool IsMemoryLoadOrStore(Instruction inst)
{
return inst == Instruction.Load || inst == Instruction.Store;
}
private static bool ConstTooLong(Operand constOp, OperandType accessType)
{
if ((uint)constOp.Value != constOp.Value)
{
return true;
}
return !CodeGenCommon.ConstFitsOnUImm12(constOp.AsInt32(), accessType);
}
}
}