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JIT: fix issue with out of order importer spilling around some calls #95539

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Dec 4, 2023
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39 changes: 39 additions & 0 deletions src/coreclr/jit/importer.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -453,6 +453,11 @@ void Compiler::impAppendStmt(Statement* stmt, unsigned chkLevel, bool checkConsu
}
}

// In the case of GT_RET_EXPR any subsequent spills will appear in the wrong place -- after
// the call. We need to move them to before the call
//
Statement* lastStmt = impLastStmt;

if ((dstVarDsc != nullptr) && !dstVarDsc->IsAddressExposed() && !dstVarDsc->lvHasLdAddrOp)
{
impSpillLclRefs(lvaGetLclNum(dstVarDsc), chkLevel);
Expand Down Expand Up @@ -480,6 +485,40 @@ void Compiler::impAppendStmt(Statement* stmt, unsigned chkLevel, bool checkConsu
{
impSpillSpecialSideEff();
}

if ((lastStmt != impLastStmt) && expr->OperIs(GT_RET_EXPR))
{
GenTree* const call = expr->AsRetExpr()->gtInlineCandidate;
JITDUMP("\nimpAppendStmt: after sinking a local struct store into inline candidate [%06u], we need to "
"reorder subsequent spills.\n",
dspTreeID(call));

// Move all newly appended statements to just before the call's statement.
// First, find the statement containing the call.
//
Statement* insertBeforeStmt = lastStmt;

while (insertBeforeStmt->GetRootNode() != call)
{
assert(insertBeforeStmt != impStmtList);
insertBeforeStmt = insertBeforeStmt->GetPrevStmt();
}

Statement* movingStmt = lastStmt->GetNextStmt();

JITDUMP("Moving " FMT_STMT " through " FMT_STMT " before " FMT_STMT "\n", movingStmt->GetID(),
impLastStmt->GetID(), insertBeforeStmt->GetID());

// We move these backwards, so must keep moving the insert
// point to keep them in order.
//
while (impLastStmt != lastStmt)
{
Statement* movingStmt = impExtractLastStmt();
impInsertStmtBefore(movingStmt, insertBeforeStmt);
insertBeforeStmt = movingStmt;
}
}
}

impAppendStmtCheck(stmt, chkLevel);
Expand Down
61 changes: 61 additions & 0 deletions src/tests/JIT/Regression/JitBlue/Runtime_95349/Runtime_95349.cs
Original file line number Diff line number Diff line change
@@ -0,0 +1,61 @@
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

// Issues with stack spill ordering around some GDVs
// Compile with <DebugType>None</DebugType>

using System;
using System.Runtime.CompilerServices;
using System.Threading;
using Xunit;

class P
{
virtual public (double x, double y) XY() => (0, 0);
}

class P1 : P
{
override public (double x, double y) XY() => (1, 2);
}

public class Runtime_95349
{
[MethodImpl(MethodImplOptions.NoInlining)]
static int Problem(P p, int n, (double x, double y) tuple)
{
int wn = 0;
for (int i = 0; i < n; i++)
{
(double x, double y) tupleTmp = tuple;
tuple = p.XY();
(_, double f) = tupleTmp;
wn = Wn(wn, f, tuple.y);
}

return wn;
}

[MethodImpl(MethodImplOptions.NoInlining)]
static int Wn(int wn, double f, double y)
{
wn += (f == -1) ? 1 : 0;
return wn;
}

[Fact]
public static void Test()
{
P p = new P1();
int n = 100_000;
for (int i = 0; i < 100; i++)
{
_ = Problem(p, n, (-1, -1));
Thread.Sleep(30);
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@EgorBo EgorBo Dec 2, 2023

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The repro needs Tiered Compilation, right? Then I presume you need to run some pipeline where it's not disabled (like pgo ones) (or add TC=1 in csproj)

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Yes, this needs to have a GDV expansion to expose the bug.

}

int r = Problem(p, n, (-1, -1));
Console.WriteLine($"r = {r} (expected 1)");
Assert.Equal(1, r);
}
}
Original file line number Diff line number Diff line change
@@ -0,0 +1,9 @@
<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
<Optimize>True</Optimize>
<DebugType>None</DebugType>
</PropertyGroup>
<ItemGroup>
<Compile Include="$(MSBuildProjectName).cs" />
</ItemGroup>
</Project>