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Fix 14455: _opt_relrotarg_valref test failure on amd64. (dotnet#15032)
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* fix the issue

Do not zero-initialize temps, that were created by jit and do not have GC refs.
The confusion was that `varDsc->lvIsTemp` means `short live` variable, when we wanted to ask is it IL temp or not.

* add a non-stress repro.
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Sergey Andreenko authored Nov 16, 2017
1 parent d3297ab commit 88527bb
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13 changes: 7 additions & 6 deletions src/jit/morph.cpp
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Expand Up @@ -8104,22 +8104,23 @@ void Compiler::fgMorphRecursiveFastTailCallIntoLoop(BasicBlock* block, GenTreeCa

// If compInitMem is set, we may need to zero-initialize some locals. Normally it's done in the prolog
// but this loop can't include the prolog. Since we don't have liveness information, we insert zero-initialization
// for all non-parameter non-temp locals as well as temp structs with GC fields.
// for all non-parameter IL locals as well as temp structs with GC fields.
// Liveness phase will remove unnecessary initializations.
if (info.compInitMem)
{
unsigned varNum;
LclVarDsc* varDsc;
for (varNum = 0, varDsc = lvaTable; varNum < lvaCount; varNum++, varDsc++)
{
var_types lclType = varDsc->TypeGet();
if (!varDsc->lvIsParam)
{
if (!varDsc->lvIsTemp || ((lclType == TYP_STRUCT) && (varDsc->lvStructGcCount > 0)))
var_types lclType = varDsc->TypeGet();
bool isUserLocal = (varNum < info.compLocalsCount);
bool structWithGCFields = ((lclType == TYP_STRUCT) && (varDsc->lvStructGcCount > 0));
if (isUserLocal || structWithGCFields)
{
var_types lclType = varDsc->TypeGet();
GenTreePtr lcl = gtNewLclvNode(varNum, lclType);
GenTreePtr init = nullptr;
GenTreePtr lcl = gtNewLclvNode(varNum, lclType);
GenTreePtr init = nullptr;
if (lclType == TYP_STRUCT)
{
const bool isVolatile = false;
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105 changes: 105 additions & 0 deletions tests/src/JIT/Regression/JitBlue/GitHub_14455/GitHub_14455.il
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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

// It is a non-stress repro for the issue #14455.
// growTree is optimized as fast tail call and converted to a loop.
// `starg.s 0` forces the jit to create a temp for the modifiable this.
// Before the fix the jit zero-initialized all long-live locals in the end of the loop,
// on the last iteration it set `this` to `null` and the return block was trying to use
// `null` to write `m_rightChild` in, that caused a runtime exception.


.assembly extern System.Runtime {auto}
.assembly GitHub_14455 {}

.class public auto ansi beforefieldinit Rotate.Node
extends [System.Runtime]System.Object
{
.field public class Rotate.Node m_leftChild
.field public class Rotate.Node m_rightChild
.method public hidebysig specialname rtspecialname
instance void .ctor() cil managed
{
// Code size 7 (0x7)
.maxstack 8
IL_0000: ldarg.0
IL_0001: call instance void [System.Runtime]System.Object::.ctor()
IL_0006: ret
} // end of method Node::.ctor

.method family hidebysig virtual instance void
Finalize() cil managed
{
.override [System.Runtime]System.Object::Finalize
// Code size 10 (0xa)
.maxstack 1
.try
{
IL_0000: leave.s IL_0009

} // end .try
finally
{
IL_0002: ldarg.0
IL_0003: call instance void [System.Runtime]System.Object::Finalize()
IL_0008: endfinally
} // end handler
IL_0009: ret
} // end of method Node::Finalize

.method public hidebysig instance void
growTree(int32 maxHeight) cil managed
{
// Code size 72 (0x48)
.maxstack 4
.locals init (class Rotate.Node V_0)
IL_0000: ldarg.1
IL_0001: ldc.i4.0
IL_0002: ble.s IL_0037

IL_0004: ldarg.0
IL_0005: newobj instance void Rotate.Node::.ctor()
IL_000a: stfld class Rotate.Node Rotate.Node::m_leftChild
IL_000f: ldarg.0
IL_0010: ldfld class Rotate.Node Rotate.Node::m_leftChild
IL_0015: ldarg.1
IL_0016: ldc.i4.1
IL_0017: sub
IL_0018: callvirt instance void Rotate.Node::growTree(int32)
IL_001d: ldarg.0
IL_001e: newobj instance void Rotate.Node::.ctor()
IL_0023: stfld class Rotate.Node Rotate.Node::m_rightChild
IL_0028: ldarg.0
IL_0029: ldfld class Rotate.Node Rotate.Node::m_rightChild
IL_002e: ldarg.1
IL_002f: ldc.i4.1
IL_0030: sub
IL_0031: callvirt instance void Rotate.Node::growTree(int32)
IL_0036: ret
ldarg.0
starg.s 0 // Force to create a temp for the modifiable this.
IL_0037: ldarg.0
IL_0038: ldarg.0
IL_0039: ldnull
IL_003a: dup
IL_003b: stloc.0
IL_003c: stfld class Rotate.Node Rotate.Node::m_rightChild
IL_0041: ldloc.0
IL_0042: stfld class Rotate.Node Rotate.Node::m_leftChild
IL_0047: ret
} // end of method Node::growTree

.method public hidebysig static int32 Main() cil managed
{
.entrypoint
// Code size 14 (0xe)
.maxstack 8
IL_0000: newobj instance void Rotate.Node::.ctor()
IL_0005: ldc.i4.4
IL_0006: callvirt instance void Rotate.Node::growTree(int32)
IL_000b: ldc.i4.s 100
IL_000d: ret
} // end of method Node::Main

} // end of class Rotate.Node
34 changes: 34 additions & 0 deletions tests/src/JIT/Regression/JitBlue/GitHub_14455/GitHub_14455.ilproj
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