fgMorphArgs reorders (non-call) exception-throwing arguments

[jakobbotsch]

Description

For each arg, fgMorphArgs looks for GTF_CALL and GTF_ASG to figure out if args before that one need to be spilled to temps in anticipation of sorting them. This should take GTF_EXCEPT into account as otherwise we can reorder late args that may throw exceptions.

Reproduction Steps

The following program throws DivisionByZeroException when it should throw NullReferenceException:

using System.Runtime.CompilerServices;

public class Program
{
    public static void Main(string[] args)
    {
        Foo();
    }

    [MethodImpl(MethodImplOptions.NoInlining)]
    private static void Foo()
    {
        C c = null;
        int i = 1;
        Bar(c.Field, i / 0);
    }

    [MethodImpl(MethodImplOptions.NoInlining)]
    private static void Bar(object o, int val)
    {
    }

    private class C
    {
        public object Field;
    }
}

Expected behavior

NullReferenceException

Actual behavior

DivisionByZeroException

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

cc @dotnet/jit-contrib

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Issue Details

---

Description

For each arg, fgMorphArgs looks for GTF_CALL and GTF_ASG to figure out if args before that one need to be spilled to temps in anticipation of sorting them. This should take GTF_EXCEPT into account as otherwise we can reorder late args that may throw exceptions.

Reproduction Steps

The following program throws DivisionByZeroException when it should throw NullReferenceException:

using System.Runtime.CompilerServices;

public unsafe class Program
{
    public static void Main(string[] args)
    {
        Foo();
    }

    [MethodImpl(MethodImplOptions.NoInlining)]
    private static void Foo()
    {
        C c = null;
        int i = 1;
        Bar(c.Field, i / 0);
    }

    private static void Bar(object o, int val)
    {
    }

    private class C
    {
        public object Field;
    }
}

Expected behavior

NullReferenceException

Actual behavior

DivisionByZeroException

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

cc @dotnet/jit-contrib

Author:	jakobbotsch
Assignees:	-
Labels:	area-CodeGen-coreclr, untriaged
Milestone:	-