From 36ec1bc6c023811235d9f5fb664feff09bc7b4f7 Mon Sep 17 00:00:00 2001
From: FICTURE7 <FICTURE7@gmail.com>
Date: Sat, 12 Sep 2020 19:32:53 +0400
Subject: [PATCH] Relax block ordering constraints (#1535)
* Relax block ordering constraints
Before `block.Next` had to follow `block.ListNext`, now it does not.
Instead `CodeGenerator` will now emit the necessary jump instructions
to ensure control flow.
This makes control flow and block order modifications easier. It also
eliminates some simple cases of redundant branches.
* Set PPTC version
---
.../RegisterAllocators/HybridAllocator.cs | 13 ---
.../RegisterAllocators/LinearScanAllocator.cs | 25 ++---
ARMeilleure/CodeGen/X86/CodeGenerator.cs | 25 +++--
ARMeilleure/Diagnostics/IRDumper.cs | 21 ++--
.../IntermediateRepresentation/BasicBlock.cs | 102 ++++++++++--------
.../IntermediateRepresentation/Instruction.cs | 1 -
ARMeilleure/Translation/ControlFlowGraph.cs | 94 +++++++---------
ARMeilleure/Translation/EmitterContext.cs | 44 +++++---
ARMeilleure/Translation/PTC/Ptc.cs | 2 +-
ARMeilleure/Translation/RegisterUsage.cs | 9 +-
ARMeilleure/Translation/Translator.cs | 2 -
11 files changed, 164 insertions(+), 174 deletions(-)
diff --git a/ARMeilleure/CodeGen/RegisterAllocators/HybridAllocator.cs b/ARMeilleure/CodeGen/RegisterAllocators/HybridAllocator.cs
index 21470a663b..898cc1db81 100644
--- a/ARMeilleure/CodeGen/RegisterAllocators/HybridAllocator.cs
+++ b/ARMeilleure/CodeGen/RegisterAllocators/HybridAllocator.cs
@@ -427,18 +427,5 @@ namespace ARMeilleure.CodeGen.RegisterAllocators
{
return local.Assignments.Count + local.Uses.Count;
}
-
- private static IEnumerable<BasicBlock> Successors(BasicBlock block)
- {
- if (block.Next != null)
- {
- yield return block.Next;
- }
-
- if (block.Branch != null)
- {
- yield return block.Branch;
- }
- }
}
}
\ No newline at end of file
diff --git a/ARMeilleure/CodeGen/RegisterAllocators/LinearScanAllocator.cs b/ARMeilleure/CodeGen/RegisterAllocators/LinearScanAllocator.cs
index 01bb9554d5..71739d436e 100644
--- a/ARMeilleure/CodeGen/RegisterAllocators/LinearScanAllocator.cs
+++ b/ARMeilleure/CodeGen/RegisterAllocators/LinearScanAllocator.cs
@@ -626,16 +626,11 @@ namespace ARMeilleure.CodeGen.RegisterAllocators
continue;
}
- bool hasSingleOrNoSuccessor = block.Next == null || block.Branch == null;
+ bool hasSingleOrNoSuccessor = block.SuccessorCount <= 1;
- for (int i = 0; i < 2; i++)
+ for (int i = 0; i < block.SuccessorCount; i++)
{
- // This used to use an enumerable, but it ended up generating a lot of garbage, so now it is a loop.
- BasicBlock successor = (i == 0) ? block.Next : block.Branch;
- if (successor == null)
- {
- continue;
- }
+ BasicBlock successor = block.GetSuccessor(i);
int succIndex = successor.Index;
@@ -643,7 +638,7 @@ namespace ARMeilleure.CodeGen.RegisterAllocators
// (the successor before the split) should be right after it.
if (IsSplitEdgeBlock(successor))
{
- succIndex = FirstSuccessor(successor).Index;
+ succIndex = successor.GetSuccessor(0).Index;
}
CopyResolver copyResolver = new CopyResolver();
@@ -883,10 +878,11 @@ namespace ARMeilleure.CodeGen.RegisterAllocators
BitMap liveOut = blkLiveOut[block.Index];
- if ((block.Next != null && liveOut.Set(blkLiveIn[block.Next.Index])) ||
- (block.Branch != null && liveOut.Set(blkLiveIn[block.Branch.Index])))
+ for (int i = 0; i < block.SuccessorCount; i++)
{
- modified = true;
+ BasicBlock succ = block.GetSuccessor(i);
+
+ modified |= liveOut.Set(blkLiveIn[succ.Index]);
}
BitMap liveIn = blkLiveIn[block.Index];
@@ -1002,11 +998,6 @@ namespace ARMeilleure.CodeGen.RegisterAllocators
return (register.Index << 1) | (register.Type == RegisterType.Vector ? 1 : 0);
}
- private static BasicBlock FirstSuccessor(BasicBlock block)
- {
- return block.Next ?? block.Branch;
- }
-
private static IEnumerable<Node> BottomOperations(BasicBlock block)
{
Node node = block.Operations.Last;
diff --git a/ARMeilleure/CodeGen/X86/CodeGenerator.cs b/ARMeilleure/CodeGen/X86/CodeGenerator.cs
index f2d4c46276..a51f4a1375 100644
--- a/ARMeilleure/CodeGen/X86/CodeGenerator.cs
+++ b/ARMeilleure/CodeGen/X86/CodeGenerator.cs
@@ -32,7 +32,6 @@ namespace ARMeilleure.CodeGen.X86
Add(Instruction.BitwiseExclusiveOr, GenerateBitwiseExclusiveOr);
Add(Instruction.BitwiseNot, GenerateBitwiseNot);
Add(Instruction.BitwiseOr, GenerateBitwiseOr);
- Add(Instruction.Branch, GenerateBranch);
Add(Instruction.BranchIf, GenerateBranchIf);
Add(Instruction.ByteSwap, GenerateByteSwap);
Add(Instruction.Call, GenerateCall);
@@ -168,6 +167,23 @@ namespace ARMeilleure.CodeGen.X86
GenerateOperation(context, operation);
}
}
+
+ if (block.SuccessorCount == 0)
+ {
+ // The only blocks which can have 0 successors are exit blocks.
+ Debug.Assert(block.Operations.Last is Operation operation &&
+ (operation.Instruction == Instruction.Tailcall ||
+ operation.Instruction == Instruction.Return));
+ }
+ else
+ {
+ BasicBlock succ = block.GetSuccessor(0);
+
+ if (succ != block.ListNext)
+ {
+ context.JumpTo(succ);
+ }
+ }
}
Logger.EndPass(PassName.CodeGeneration);
@@ -512,11 +528,6 @@ namespace ARMeilleure.CodeGen.X86
context.Assembler.Or(dest, src2, dest.Type);
}
- private static void GenerateBranch(CodeGenContext context, Operation operation)
- {
- context.JumpTo(context.CurrBlock.Branch);
- }
-
private static void GenerateBranchIf(CodeGenContext context, Operation operation)
{
Operand comp = operation.GetSource(2);
@@ -527,7 +538,7 @@ namespace ARMeilleure.CodeGen.X86
GenerateCompareCommon(context, operation);
- context.JumpTo(cond, context.CurrBlock.Branch);
+ context.JumpTo(cond, context.CurrBlock.GetSuccessor(1));
}
private static void GenerateByteSwap(CodeGenContext context, Operation operation)
diff --git a/ARMeilleure/Diagnostics/IRDumper.cs b/ARMeilleure/Diagnostics/IRDumper.cs
index 0f0d72c157..90eb2300ac 100644
--- a/ARMeilleure/Diagnostics/IRDumper.cs
+++ b/ARMeilleure/Diagnostics/IRDumper.cs
@@ -57,17 +57,20 @@ namespace ARMeilleure.Diagnostics
{
DumpBlockName(block);
- if (block.Next != null)
+ if (block.SuccessorCount > 0)
{
- _builder.Append(" (next ");
- DumpBlockName(block.Next);
- _builder.Append(')');
- }
+ _builder.Append(" (");
+
+ for (int i = 0; i < block.SuccessorCount; i++)
+ {
+ DumpBlockName(block.GetSuccessor(i));
+
+ if (i < block.SuccessorCount - 1)
+ {
+ _builder.Append(", ");
+ }
+ }
- if (block.Branch != null)
- {
- _builder.Append(" (branch ");
- DumpBlockName(block.Branch);
_builder.Append(')');
}
diff --git a/ARMeilleure/IntermediateRepresentation/BasicBlock.cs b/ARMeilleure/IntermediateRepresentation/BasicBlock.cs
index ac48ac8eb2..640978fe7f 100644
--- a/ARMeilleure/IntermediateRepresentation/BasicBlock.cs
+++ b/ARMeilleure/IntermediateRepresentation/BasicBlock.cs
@@ -1,9 +1,12 @@
+using System;
using System.Collections.Generic;
namespace ARMeilleure.IntermediateRepresentation
{
class BasicBlock : IIntrusiveListNode<BasicBlock>
{
+ private readonly List<BasicBlock> _successors = new List<BasicBlock>();
+
public int Index { get; set; }
public BasicBlock ListPrevious { get; set; }
@@ -11,69 +14,82 @@ namespace ARMeilleure.IntermediateRepresentation
public IntrusiveList<Node> Operations { get; }
- private BasicBlock _next;
- private BasicBlock _branch;
-
- public BasicBlock Next
- {
- get => _next;
- set => _next = AddSuccessor(_next, value);
- }
-
- public BasicBlock Branch
- {
- get => _branch;
- set => _branch = AddSuccessor(_branch, value);
- }
-
public List<BasicBlock> Predecessors { get; }
public HashSet<BasicBlock> DominanceFrontiers { get; }
-
public BasicBlock ImmediateDominator { get; set; }
- public BasicBlock()
+ public int SuccessorCount => _successors.Count;
+
+ public BasicBlock() : this(index: -1) { }
+
+ public BasicBlock(int index)
{
Operations = new IntrusiveList<Node>();
-
Predecessors = new List<BasicBlock>();
-
DominanceFrontiers = new HashSet<BasicBlock>();
- Index = -1;
- }
-
- public BasicBlock(int index) : this()
- {
Index = index;
}
- private BasicBlock AddSuccessor(BasicBlock oldBlock, BasicBlock newBlock)
+ public void AddSuccessor(BasicBlock block)
{
- oldBlock?.Predecessors.Remove(this);
- newBlock?.Predecessors.Add(this);
+ if (block == null)
+ {
+ throw new ArgumentNullException(nameof(block));
+ }
- return newBlock;
+ block.Predecessors.Add(this);
+
+ _successors.Add(block);
+ }
+
+ public void RemoveSuccessor(int index)
+ {
+ BasicBlock oldBlock = _successors[index];
+
+ oldBlock.Predecessors.Remove(this);
+
+ _successors.RemoveAt(index);
+ }
+
+ public BasicBlock GetSuccessor(int index)
+ {
+ return _successors[index];
+ }
+
+ public void SetSuccessor(int index, BasicBlock block)
+ {
+ if (block == null)
+ {
+ throw new ArgumentNullException(nameof(block));
+ }
+
+ BasicBlock oldBlock = _successors[index];
+
+ oldBlock.Predecessors.Remove(this);
+ block.Predecessors.Add(this);
+
+ _successors[index] = block;
}
public void Append(Node node)
{
- // If the branch block is not null, then the list of operations
- // should end with a branch instruction. We insert the new operation
- // before this branch.
- if (_branch != null || (Operations.Last != null && IsLeafBlock()))
- {
- Operations.AddBefore(Operations.Last, node);
- }
- else
- {
- Operations.AddLast(node);
- }
- }
+ var lastOp = Operations.Last as Operation;
- private bool IsLeafBlock()
- {
- return _branch == null && _next == null;
+ // Append node before terminal or to end if no terminal.
+ switch (lastOp?.Instruction)
+ {
+ case Instruction.Return:
+ case Instruction.Tailcall:
+ case Instruction.BranchIf:
+ Operations.AddBefore(lastOp, node);
+ break;
+
+ default:
+ Operations.AddLast(node);
+ break;
+ }
}
public Node GetLastOp()
diff --git a/ARMeilleure/IntermediateRepresentation/Instruction.cs b/ARMeilleure/IntermediateRepresentation/Instruction.cs
index c583a2f2b2..938a528dff 100644
--- a/ARMeilleure/IntermediateRepresentation/Instruction.cs
+++ b/ARMeilleure/IntermediateRepresentation/Instruction.cs
@@ -7,7 +7,6 @@ namespace ARMeilleure.IntermediateRepresentation
BitwiseExclusiveOr,
BitwiseNot,
BitwiseOr,
- Branch,
BranchIf,
ByteSwap,
Call,
diff --git a/ARMeilleure/Translation/ControlFlowGraph.cs b/ARMeilleure/Translation/ControlFlowGraph.cs
index 16b406ab0d..3496353442 100644
--- a/ARMeilleure/Translation/ControlFlowGraph.cs
+++ b/ARMeilleure/Translation/ControlFlowGraph.cs
@@ -8,47 +8,48 @@ namespace ARMeilleure.Translation
class ControlFlowGraph
{
public BasicBlock Entry { get; }
-
public IntrusiveList<BasicBlock> Blocks { get; }
-
public BasicBlock[] PostOrderBlocks { get; }
-
public int[] PostOrderMap { get; }
public ControlFlowGraph(BasicBlock entry, IntrusiveList<BasicBlock> blocks)
{
- Entry = entry;
+ Entry = entry;
Blocks = blocks;
RemoveUnreachableBlocks(blocks);
- HashSet<BasicBlock> visited = new HashSet<BasicBlock>();
-
- Stack<BasicBlock> blockStack = new Stack<BasicBlock>();
+ var visited = new HashSet<BasicBlock>();
+ var blockStack = new Stack<BasicBlock>();
PostOrderBlocks = new BasicBlock[blocks.Count];
-
PostOrderMap = new int[blocks.Count];
visited.Add(entry);
-
blockStack.Push(entry);
int index = 0;
while (blockStack.TryPop(out BasicBlock block))
{
- if (block.Next != null && visited.Add(block.Next))
+ bool visitedNew = false;
+
+ for (int i = 0; i < block.SuccessorCount; i++)
{
- blockStack.Push(block);
- blockStack.Push(block.Next);
+ BasicBlock succ = block.GetSuccessor(i);
+
+ if (visited.Add(succ))
+ {
+ blockStack.Push(block);
+ blockStack.Push(succ);
+
+ visitedNew = true;
+
+ break;
+ }
}
- else if (block.Branch != null && visited.Add(block.Branch))
- {
- blockStack.Push(block);
- blockStack.Push(block.Branch);
- }
- else
+
+ if (!visitedNew)
{
PostOrderMap[block.Index] = index;
@@ -59,26 +60,24 @@ namespace ARMeilleure.Translation
private void RemoveUnreachableBlocks(IntrusiveList<BasicBlock> blocks)
{
- HashSet<BasicBlock> visited = new HashSet<BasicBlock>();
-
- Queue<BasicBlock> workQueue = new Queue<BasicBlock>();
+ var visited = new HashSet<BasicBlock>();
+ var workQueue = new Queue<BasicBlock>();
visited.Add(Entry);
-
workQueue.Enqueue(Entry);
while (workQueue.TryDequeue(out BasicBlock block))
{
Debug.Assert(block.Index != -1, "Invalid block index.");
- if (block.Next != null && visited.Add(block.Next))
+ for (int i = 0; i < block.SuccessorCount; i++)
{
- workQueue.Enqueue(block.Next);
- }
+ BasicBlock succ = block.GetSuccessor(i);
- if (block.Branch != null && visited.Add(block.Branch))
- {
- workQueue.Enqueue(block.Branch);
+ if (visited.Add(succ))
+ {
+ workQueue.Enqueue(succ);
+ }
}
}
@@ -93,8 +92,10 @@ namespace ARMeilleure.Translation
if (!visited.Contains(block))
{
- block.Next = null;
- block.Branch = null;
+ while (block.SuccessorCount > 0)
+ {
+ block.RemoveSuccessor(index: block.SuccessorCount - 1);
+ }
blocks.Remove(block);
}
@@ -112,14 +113,12 @@ namespace ARMeilleure.Translation
{
BasicBlock splitBlock = new BasicBlock(Blocks.Count);
- if (predecessor.Next == successor)
+ for (int i = 0; i < predecessor.SuccessorCount; i++)
{
- predecessor.Next = splitBlock;
- }
-
- if (predecessor.Branch == successor)
- {
- predecessor.Branch = splitBlock;
+ if (predecessor.GetSuccessor(i) == successor)
+ {
+ predecessor.SetSuccessor(i, splitBlock);
+ }
}
if (splitBlock.Predecessors.Count == 0)
@@ -127,26 +126,7 @@ namespace ARMeilleure.Translation
throw new ArgumentException("Predecessor and successor are not connected.");
}
- // Insert the new block on the list of blocks.
- BasicBlock succPrev = successor.ListPrevious;
-
- if (succPrev != null && succPrev != predecessor && succPrev.Next == successor)
- {
- // Can't insert after the predecessor or before the successor.
- // Here, we insert it before the successor by also spliting another
- // edge (the one between the block before "successor" and "successor").
- BasicBlock splitBlock2 = new BasicBlock(splitBlock.Index + 1);
-
- succPrev.Next = splitBlock2;
-
- splitBlock2.Branch = successor;
-
- splitBlock2.Operations.AddLast(OperationHelper.Operation(Instruction.Branch, null));
-
- Blocks.AddBefore(successor, splitBlock2);
- }
-
- splitBlock.Next = successor;
+ splitBlock.AddSuccessor(successor);
Blocks.AddBefore(successor, splitBlock);
diff --git a/ARMeilleure/Translation/EmitterContext.cs b/ARMeilleure/Translation/EmitterContext.cs
index a6cc55dfb9..2261fb8774 100644
--- a/ARMeilleure/Translation/EmitterContext.cs
+++ b/ARMeilleure/Translation/EmitterContext.cs
@@ -13,18 +13,17 @@ namespace ARMeilleure.Translation
class EmitterContext
{
- private Dictionary<Operand, BasicBlock> _irLabels;
-
- private IntrusiveList<BasicBlock> _irBlocks;
+ private readonly Dictionary<Operand, BasicBlock> _irLabels;
+ private readonly IntrusiveList<BasicBlock> _irBlocks;
private BasicBlock _irBlock;
+ private BasicBlock _ifBlock;
private bool _needsNewBlock;
public EmitterContext()
{
_irLabels = new Dictionary<Operand, BasicBlock>();
-
_irBlocks = new IntrusiveList<BasicBlock>();
_needsNewBlock = true;
@@ -57,16 +56,16 @@ namespace ARMeilleure.Translation
public void Branch(Operand label)
{
- Add(Instruction.Branch, null);
+ NewNextBlockIfNeeded();
- BranchToLabel(label);
+ BranchToLabel(label, uncond: true);
}
public void BranchIf(Operand label, Operand op1, Operand op2, Comparison comp)
{
Add(Instruction.BranchIf, null, op1, op2, Const((int)comp));
- BranchToLabel(label);
+ BranchToLabel(label, uncond: false);
}
public void BranchIfFalse(Operand label, Operand op1)
@@ -574,10 +573,7 @@ namespace ARMeilleure.Translation
private Operand Add(Intrinsic intrin, Operand dest, params Operand[] sources)
{
- if (_needsNewBlock)
- {
- NewNextBlock();
- }
+ NewNextBlockIfNeeded();
IntrinsicOperation operation = new IntrinsicOperation(intrin, dest, sources);
@@ -586,7 +582,7 @@ namespace ARMeilleure.Translation
return dest;
}
- private void BranchToLabel(Operand label)
+ private void BranchToLabel(Operand label, bool uncond)
{
if (!_irLabels.TryGetValue(label, out BasicBlock branchBlock))
{
@@ -595,7 +591,15 @@ namespace ARMeilleure.Translation
_irLabels.Add(label, branchBlock);
}
- _irBlock.Branch = branchBlock;
+ if (uncond)
+ {
+ _irBlock.AddSuccessor(branchBlock);
+ }
+ else
+ {
+ // Defer registration of successor to _irBlock so that the order of successors is correct.
+ _ifBlock = branchBlock;
+ }
_needsNewBlock = true;
}
@@ -629,9 +633,16 @@ namespace ARMeilleure.Translation
private void NextBlock(BasicBlock nextBlock)
{
- if (_irBlock != null && !EndsWithUnconditional(_irBlock))
+ if (_irBlock != null && _irBlock.SuccessorCount == 0 && !EndsWithUnconditional(_irBlock))
{
- _irBlock.Next = nextBlock;
+ _irBlock.AddSuccessor(nextBlock);
+
+ if (_ifBlock != null)
+ {
+ _irBlock.AddSuccessor(_ifBlock);
+
+ _ifBlock = null;
+ }
}
_irBlock = nextBlock;
@@ -642,8 +653,7 @@ namespace ARMeilleure.Translation
private static bool EndsWithUnconditional(BasicBlock block)
{
return block.Operations.Last is Operation lastOp &&
- (lastOp.Instruction == Instruction.Branch ||
- lastOp.Instruction == Instruction.Return ||
+ (lastOp.Instruction == Instruction.Return ||
lastOp.Instruction == Instruction.Tailcall);
}
diff --git a/ARMeilleure/Translation/PTC/Ptc.cs b/ARMeilleure/Translation/PTC/Ptc.cs
index eebf80759c..ae884ab65b 100644
--- a/ARMeilleure/Translation/PTC/Ptc.cs
+++ b/ARMeilleure/Translation/PTC/Ptc.cs
@@ -21,7 +21,7 @@ namespace ARMeilleure.Translation.PTC
{
private const string HeaderMagic = "PTChd";
- private const int InternalVersion = 1537; //! To be incremented manually for each change to the ARMeilleure project.
+ private const int InternalVersion = 1535; //! To be incremented manually for each change to the ARMeilleure project.
private const string ActualDir = "0";
private const string BackupDir = "1";
diff --git a/ARMeilleure/Translation/RegisterUsage.cs b/ARMeilleure/Translation/RegisterUsage.cs
index d512428564..6a21ae2a93 100644
--- a/ARMeilleure/Translation/RegisterUsage.cs
+++ b/ARMeilleure/Translation/RegisterUsage.cs
@@ -171,14 +171,9 @@ namespace ARMeilleure.Translation
RegisterMask inputs = localInputs[block.Index];
- if (block.Next != null)
+ for (int i = 0; i < block.SuccessorCount; i++)
{
- inputs |= globalInputs[block.Next.Index];
- }
-
- if (block.Branch != null)
- {
- inputs |= globalInputs[block.Branch.Index];
+ inputs |= globalInputs[block.GetSuccessor(i).Index];
}
inputs &= ~globalCmnOutputs[block.Index];
diff --git a/ARMeilleure/Translation/Translator.cs b/ARMeilleure/Translation/Translator.cs
index d1404796ac..1a02bce0cf 100644
--- a/ARMeilleure/Translation/Translator.cs
+++ b/ARMeilleure/Translation/Translator.cs
@@ -309,8 +309,6 @@ namespace ARMeilleure.Translation
context.Return(Const(0L));
- context.Branch(lblExit);
-
context.MarkLabel(lblNonZero);
count = context.Subtract(count, Const(1));