using Ryujinx.Graphics.Shader.IntermediateRepresentation;
using System.Collections.Generic;
namespace Ryujinx.Graphics.Shader.Translation
{
static class Dominance
// Those methods are an implementation of the algorithms on "A Simple, Fast Dominance Algorithm".
// https://www.cs.rice.edu/~keith/EMBED/dom.pdf
public static void FindDominators(BasicBlock entry, int blocksCount)
HashSet<BasicBlock> visited = new HashSet<BasicBlock>();
Stack<BasicBlock> blockStack = new Stack<BasicBlock>();
List<BasicBlock> postOrderBlocks = new List<BasicBlock>(blocksCount);
int[] postOrderMap = new int[blocksCount];
visited.Add(entry);
blockStack.Push(entry);
while (blockStack.TryPop(out BasicBlock block))
if (block.Next != null && visited.Add(block.Next))
blockStack.Push(block);
blockStack.Push(block.Next);
}
else if (block.Branch != null && visited.Add(block.Branch))
blockStack.Push(block.Branch);
else
postOrderMap[block.Index] = postOrderBlocks.Count;
postOrderBlocks.Add(block);
BasicBlock Intersect(BasicBlock block1, BasicBlock block2)
while (block1 != block2)
while (postOrderMap[block1.Index] < postOrderMap[block2.Index])
block1 = block1.ImmediateDominator;
while (postOrderMap[block2.Index] < postOrderMap[block1.Index])
block2 = block2.ImmediateDominator;
return block1;
entry.ImmediateDominator = entry;
bool modified;
do
modified = false;
for (int blkIndex = postOrderBlocks.Count - 2; blkIndex >= 0; blkIndex--)
BasicBlock block = postOrderBlocks[blkIndex];
BasicBlock newIDom = null;
foreach (BasicBlock predecessor in block.Predecessors)
if (predecessor.ImmediateDominator != null)
if (newIDom != null)
newIDom = Intersect(predecessor, newIDom);
newIDom = predecessor;
if (block.ImmediateDominator != newIDom)
block.ImmediateDominator = newIDom;
modified = true;
while (modified);
public static void FindDominanceFrontiers(BasicBlock[] blocks)
for (int blkIndex = 0; blkIndex < blocks.Length; blkIndex++)
BasicBlock block = blocks[blkIndex];
if (block.Predecessors.Count < 2)
continue;
for (int pBlkIndex = 0; pBlkIndex < block.Predecessors.Count; pBlkIndex++)
BasicBlock current = block.Predecessors[pBlkIndex];
while (current != block.ImmediateDominator)
current.DominanceFrontiers.Add(block);
current = current.ImmediateDominator;