From d25a084858438dd1188113efb76548916c2da9de Mon Sep 17 00:00:00 2001
From: gdkchan <gab.dark.100@gmail.com>
Date: Wed, 19 Jun 2024 09:25:47 -0300
Subject: [PATCH] JIT: Ensure entry block has no predecessors on RegisterUsage
pass (#6951)
---
src/ARMeilleure/Translation/ControlFlowGraph.cs | 11 ++++++++++-
src/ARMeilleure/Translation/RegisterUsage.cs | 13 ++++++++++++-
2 files changed, 22 insertions(+), 2 deletions(-)
diff --git a/src/ARMeilleure/Translation/ControlFlowGraph.cs b/src/ARMeilleure/Translation/ControlFlowGraph.cs
index 3ead49c93..45b092ec5 100644
--- a/src/ARMeilleure/Translation/ControlFlowGraph.cs
+++ b/src/ARMeilleure/Translation/ControlFlowGraph.cs
@@ -11,7 +11,7 @@ namespace ARMeilleure.Translation
private int[] _postOrderMap;
public int LocalsCount { get; private set; }
- public BasicBlock Entry { get; }
+ public BasicBlock Entry { get; private set; }
public IntrusiveList<BasicBlock> Blocks { get; }
public BasicBlock[] PostOrderBlocks => _postOrderBlocks;
public int[] PostOrderMap => _postOrderMap;
@@ -34,6 +34,15 @@ namespace ARMeilleure.Translation
return result;
}
+ public void UpdateEntry(BasicBlock newEntry)
+ {
+ newEntry.AddSuccessor(Entry);
+
+ Entry = newEntry;
+ Blocks.AddFirst(newEntry);
+ Update();
+ }
+
public void Update()
{
RemoveUnreachableBlocks(Blocks);
diff --git a/src/ARMeilleure/Translation/RegisterUsage.cs b/src/ARMeilleure/Translation/RegisterUsage.cs
index c8c250626..472b0f67b 100644
--- a/src/ARMeilleure/Translation/RegisterUsage.cs
+++ b/src/ARMeilleure/Translation/RegisterUsage.cs
@@ -89,6 +89,17 @@ namespace ARMeilleure.Translation
public static void RunPass(ControlFlowGraph cfg, ExecutionMode mode)
{
+ if (cfg.Entry.Predecessors.Count != 0)
+ {
+ // We expect the entry block to have no predecessors.
+ // This is required because we have a implicit context load at the start of the function,
+ // but if there is a jump to the start of the function, the context load would trash the modified values.
+ // Here we insert a new entry block that will jump to the existing entry block.
+ BasicBlock newEntry = new BasicBlock(cfg.Blocks.Count);
+
+ cfg.UpdateEntry(newEntry);
+ }
+
// Compute local register inputs and outputs used inside blocks.
RegisterMask[] localInputs = new RegisterMask[cfg.Blocks.Count];
RegisterMask[] localOutputs = new RegisterMask[cfg.Blocks.Count];
@@ -201,7 +212,7 @@ namespace ARMeilleure.Translation
// The only block without any predecessor should be the entry block.
// It always needs a context load as it is the first block to run.
- if (block.Predecessors.Count == 0 || hasContextLoad)
+ if (block == cfg.Entry || hasContextLoad)
{
long vecMask = globalInputs[block.Index].VecMask;
long intMask = globalInputs[block.Index].IntMask;