Optimize XMAD instruction sequence into a single 32-bit multiply when possible

See merge request [ryubing/ryujinx!24](https://git.ryujinx.app/ryubing/ryujinx/-/merge_requests/24)

src/Ryujinx.Graphics.Shader/Translation/Optimizations/Optimizer.cs

@@ -9,6 +9,11 @@ namespace Ryujinx.Graphics.Shader.Translation.Optimizations
     {
         public static void RunPass(TransformContext context)
         {
+            for (int blkIndex = 0; blkIndex < context.Blocks.Length; blkIndex++)
+            {
+                XmadOptimizer.RunPass(context.Blocks[blkIndex]);
+            }
+
             RunOptimizationPasses(context.Blocks, context.ResourceManager);
 
             // TODO: Some of those are not optimizations and shouldn't be here.
@@ -355,7 +360,7 @@ namespace Ryujinx.Graphics.Shader.Translation.Optimizations
             operation.TurnIntoCopy(attrMulLhs);
         }
 
-        private static void RemoveNode(BasicBlock block, LinkedListNode<INode> llNode)
+        public static void RemoveNode(BasicBlock block, LinkedListNode<INode> llNode)
         {
             // Remove a node from the nodes list, and also remove itself
             // from all the use lists on the operands that this node uses.

src/Ryujinx.Graphics.Shader/Translation/Optimizations/XmadOptimizer.cs

@@ -0,0 +1,342 @@
+using Ryujinx.Graphics.Shader.IntermediateRepresentation;
+using System.Collections.Generic;
+
+namespace Ryujinx.Graphics.Shader.Translation.Optimizations
+{
+    static class XmadOptimizer
+    {
+        public static void RunPass(BasicBlock block)
+        {
+            for (LinkedListNode<INode> node = block.Operations.First; node != null; node = node.Next)
+            {
+                if (!(node.Value is Operation operation))
+                {
+                    continue;
+                }
+
+                if (TryMatchXmadPattern(operation, out Operand x, out Operand y, out Operand addend))
+                {
+                    LinkedListNode<INode> nextNode;
+
+                    if (addend != null)
+                    {
+                        Operand temp = OperandHelper.Local();
+
+                        nextNode = block.Operations.AddAfter(node, new Operation(Instruction.Multiply, temp, x, y));
+                        nextNode = block.Operations.AddAfter(nextNode, new Operation(Instruction.Add, operation.Dest, temp, addend));
+                    }
+                    else
+                    {
+                        nextNode = block.Operations.AddAfter(node, new Operation(Instruction.Multiply, operation.Dest, x, y));
+                    }
+
+                    Optimizer.RemoveNode(block, node);
+                    node = nextNode;
+                }
+            }
+        }
+
+        private static bool TryMatchXmadPattern(Operation operation, out Operand x, out Operand y, out Operand addend)
+        {
+            return TryMatchXmad32x32Pattern(operation, out x, out y, out addend) ||
+                   TryMatchXmad32x16Pattern(operation, out x, out y, out addend);
+        }
+
+        private static bool TryMatchXmad32x32Pattern(Operation operation, out Operand x, out Operand y, out Operand addend)
+        {
+            x = null;
+            y = null;
+            addend = null;
+
+            if (operation.Inst != Instruction.Add)
+            {
+                return false;
+            }
+
+            Operand src1 = operation.GetSource(0);
+            Operand src2 = operation.GetSource(1);
+
+            if (!(src2.AsgOp is Operation addOp) || addOp.Inst != Instruction.Add)
+            {
+                return false;
+            }
+
+            Operand lowTimesLowResult = GetCopySource(addOp.GetSource(0));
+
+            if (!(lowTimesLowResult.AsgOp is Operation lowTimesLowOp))
+            {
+                return false;
+            }
+
+            if (!TryMatchLowTimesLow(lowTimesLowOp, out x, out y, out addend))
+            {
+                return false;
+            }
+
+            Operand lowTimesHighResult = GetCopySource(GetShifted16Source(addOp.GetSource(1), Instruction.ShiftLeft));
+
+            if (!(lowTimesHighResult.AsgOp is Operation lowTimesHighOp))
+            {
+                return false;
+            }
+
+            if (!TryMatchLowTimesHigh(lowTimesHighOp, x, y))
+            {
+                return false;
+            }
+
+            if (!(src1.AsgOp is Operation highTimesHighOp))
+            {
+                return false;
+            }
+
+            if (!TryMatchHighTimesHigh(highTimesHighOp, x, lowTimesHighResult))
+            {
+                return false;
+            }
+
+            return true;
+        }
+
+        private static bool TryMatchXmad32x16Pattern(Operation operation, out Operand x, out Operand y, out Operand addend)
+        {
+            x = null;
+            y = null;
+            addend = null;
+
+            if (operation.Inst != Instruction.Add)
+            {
+                return false;
+            }
+
+            Operand src1 = operation.GetSource(0);
+            Operand src2 = operation.GetSource(1);
+
+            Operand lowTimesLowResult = GetCopySource(src2);
+
+            if (!(lowTimesLowResult.AsgOp is Operation lowTimesLowOp))
+            {
+                return false;
+            }
+
+            if (!TryMatchLowTimesLow(lowTimesLowOp, out x, out y, out addend))
+            {
+                return false;
+            }
+
+            Operand highTimesLowResult = src1;
+
+            if (!(highTimesLowResult.AsgOp is Operation highTimesLowOp))
+            {
+                return false;
+            }
+
+            if (!TryMatchHighTimesLow(highTimesLowOp, x, y))
+            {
+                return false;
+            }
+
+            return y.Type == OperandType.Constant && (ushort)y.Value == y.Value;
+        }
+
+        private static bool TryMatchLowTimesLow(Operation operation, out Operand x, out Operand y, out Operand addend)
+        {
+            // x = x & 0xFFFF
+            // y = y & 0xFFFF
+            // lowTimesLow = x * y
+
+            x = null;
+            y = null;
+            addend = null;
+
+            if (operation.Inst == Instruction.Add)
+            {
+                if (!(operation.GetSource(0).AsgOp is Operation mulOp))
+                {
+                    return false;
+                }
+
+                addend = operation.GetSource(1);
+                operation = mulOp;
+            }
+
+            if (operation.Inst != Instruction.Multiply)
+            {
+                return false;
+            }
+
+            Operand src1 = GetMasked16Source(operation.GetSource(0));
+            Operand src2 = GetMasked16Source(operation.GetSource(1));
+
+            if (src1 == null || src2 == null)
+            {
+                return false;
+            }
+
+            x = src1;
+            y = src2;
+
+            return true;
+        }
+
+        private static bool TryMatchLowTimesHigh(Operation operation, Operand x, Operand y)
+        {
+            // xLow = x & 0xFFFF
+            // yHigh = y >> 16
+            // lowTimesHigh = xLow * yHigh
+            // result = (lowTimesHigh & 0xFFFF) | (y << 16)
+
+            if (operation.Inst != Instruction.BitwiseOr)
+            {
+                return false;
+            }
+
+            Operand mulResult = GetMasked16Source(operation.GetSource(0));
+
+            if (mulResult == null)
+            {
+                return false;
+            }
+
+            mulResult = GetCopySource(mulResult);
+
+            if (!(mulResult.AsgOp is Operation mulOp) || mulOp.Inst != Instruction.Multiply)
+            {
+                return false;
+            }
+
+            if (GetMasked16Source(mulOp.GetSource(0)) != x)
+            {
+                return false;
+            }
+
+            if (GetShifted16Source(mulOp.GetSource(1), Instruction.ShiftRightU32) != y)
+            {
+                return false;
+            }
+
+            if (GetShifted16Source(operation.GetSource(1), Instruction.ShiftLeft) != y)
+            {
+                return false;
+            }
+
+            return true;
+        }
+
+        private static bool TryMatchHighTimesLow(Operation operation, Operand x, Operand y)
+        {
+            // xHigh = x >> 16
+            // yLow = y & 0xFFFF
+            // highTimesLow = xHigh * yLow
+            // result = highTimesLow << 16
+
+            if (operation.Inst != Instruction.ShiftLeft || !IsConst(operation.GetSource(1), 16))
+            {
+                return false;
+            }
+
+            Operand mulResult = operation.GetSource(0);
+
+            if (!(mulResult.AsgOp is Operation mulOp) || mulOp.Inst != Instruction.Multiply)
+            {
+                return false;
+            }
+
+            if (GetShifted16Source(mulOp.GetSource(0), Instruction.ShiftRightU32) != x)
+            {
+                return false;
+            }
+
+            Operand src2 = GetMasked16Source(mulOp.GetSource(1));
+
+            if (src2.Type != y.Type || src2.Value != y.Value)
+            {
+                return false;
+            }
+
+            return true;
+        }
+
+        private static bool TryMatchHighTimesHigh(Operation operation, Operand x, Operand lowTimesHighResult)
+        {
+            // xHigh = x >> 16
+            // lowTimesHighResultHigh = lowTimesHighResult >> 16
+            // highTimesHigh = xHigh * lowTimesHighResultHigh
+            // result = highTimesHigh << 16
+
+            if (operation.Inst != Instruction.ShiftLeft || !IsConst(operation.GetSource(1), 16))
+            {
+                return false;
+            }
+
+            Operand mulResult = operation.GetSource(0);
+
+            if (!(mulResult.AsgOp is Operation mulOp) || mulOp.Inst != Instruction.Multiply)
+            {
+                return false;
+            }
+
+            if (GetShifted16Source(mulOp.GetSource(0), Instruction.ShiftRightU32) != x)
+            {
+                return false;
+            }
+
+            if (GetCopySource(GetShifted16Source(mulOp.GetSource(1), Instruction.ShiftRightU32)) != lowTimesHighResult)
+            {
+                return false;
+            }
+
+            return true;
+        }
+
+        private static Operand GetMasked16Source(Operand value)
+        {
+            if (!(value.AsgOp is Operation maskOp))
+            {
+                return null;
+            }
+
+            if (maskOp.Inst != Instruction.BitwiseAnd || !IsConst(maskOp.GetSource(1), ushort.MaxValue))
+            {
+                return null;
+            }
+
+            return maskOp.GetSource(0);
+        }
+
+        private static Operand GetShifted16Source(Operand value, Instruction shiftInst)
+        {
+            if (!(value.AsgOp is Operation shiftOp))
+            {
+                return null;
+            }
+
+            if (shiftOp.Inst != shiftInst || !IsConst(shiftOp.GetSource(1), 16))
+            {
+                return null;
+            }
+
+            return shiftOp.GetSource(0);
+        }
+
+        private static Operand GetCopySource(Operand value)
+        {
+            while (value.AsgOp is Operation operation && IsCopy(operation))
+            {
+                value = operation.GetSource(0);
+            }
+
+            return value;
+        }
+
+        private static bool IsCopy(Operation operation)
+        {
+            return operation.Inst == Instruction.Copy || (operation.Inst == Instruction.Add && IsConst(operation.GetSource(1), 0));
+        }
+
+        private static bool IsConst(Operand operand, int value)
+        {
+            return operand.Type == OperandType.Constant && operand.Value == value;
+        }
+    }
+}