Include the thumb bit in symbol definitions for method code nodes in crossgen2

src/coreclr/jit/emit.cpp

@@ -8516,40 +8516,10 @@ void emitter::emitOutputDataSec(dataSecDsc* sec, AllocMemChunk* chunks)
 
                 if (m_compiler->opts.compReloc)
                 {
-#ifdef TARGET_ARM
-                    // The runtime and ILC will handle setting the thumb bit on the async resumption stub entrypoint,
-                    // either directly in the emitAsyncResumeStubEntryPoint value (runtime) or will add the thumb bit
-                    // to the symbol definition (ilc). ReadyToRun is different here: it emits method symbols without the
-                    // thumb bit, then during fixups, the runtime adds the thumb bit. This works for all cases where
-                    // the method entrypoint is fixed up at runtime, but doesn't hold for the resumption stub, which is
-                    // emitted as a direct call without the typical indirection cell + fixup. This is okay in this case
-                    // (while regular method calls could not do this) because the async method and its resumption stub
-                    // are tightly coupled and effectively funclets of the same method. However, this means that
-                    // crossgen needs the reloc for the resumption stubs entrypoint to include the thumb bit. Until we
-                    // unify the behavior of crossgen with the runtime and ilc, we will work around this by emitting the
-                    // reloc with the addend for the thumb bit.
-                    if (m_compiler->IsReadyToRun())
-                    {
-                        emitRecordRelocationWithAddlDelta(&aDstRW[i].Resume, emitAsyncResumeStubEntryPoint,
-                                                          CorInfoReloc::DIRECT, 1);
-                    }
-                    else
-#endif
-                    {
-                        emitRecordRelocation(&aDstRW[i].Resume, emitAsyncResumeStubEntryPoint, CorInfoReloc::DIRECT);
-                    }
+                    emitRecordRelocation(&aDstRW[i].Resume, emitAsyncResumeStubEntryPoint, CorInfoReloc::DIRECT);
                     if (target != nullptr)
                     {
-#ifdef TARGET_ARM
-                        if (m_compiler->IsReadyToRun())
-                        {
-                            emitRecordRelocationWithAddlDelta(&aDstRW[i].DiagnosticIP, target, CorInfoReloc::DIRECT, 1);
-                        }
-                        else
-#endif
-                        {
-                            emitRecordRelocation(&aDstRW[i].DiagnosticIP, target, CorInfoReloc::DIRECT);
-                        }
+                        emitRecordRelocation(&aDstRW[i].DiagnosticIP, target, CorInfoReloc::DIRECT);
                     }
                 }
 

src/coreclr/jit/emitarm.cpp

@@ -5307,9 +5307,10 @@ BYTE* emitter::emitOutputLJ(insGroup* ig, BYTE* dst, instrDesc* i)
         assert(ins == INS_movw || ins == INS_movt);
         distVal = (ssize_t)emitOffsetToPtr(dstOffs);
 
-        // ILC defines method symbols with the thumb bit already set, so don't add it here.
-        // For ReadyToRun and non-relocatable code (runtime JIT), we set it ourselves.
-        if (!m_compiler->IsNativeAot())
+        // ILC and crossgen2 defines method symbols with the thumb bit already set, so don't add it here.
+        // Assume compilations with relocs will put the thumb bit in the symbol.
+        // For non-relocatable code (runtime JIT), we set it ourselves.
+        if (!(m_compiler->opts.compReloc))
         {
             distVal += 1;
         }

src/coreclr/tools/Common/Compiler/ObjectWriter/ObjectWriter.cs

@@ -177,7 +177,6 @@ or IMAGE_REL_BASED_THUMB_BRANCH24 or IMAGE_REL_BASED_THUMB_MOV32_PCREL &&
                     // Method symbols should be defined with the thumb bit (+1) set per the AAELF ABI
                     // convention. For BRANCH24, the encoding cannot represent the thumb bit
                     // (per AAELF formula ((S + A) | T) – P), so strip it from the symbol value.
-                    // NOTE: R2R doesn't currently add the thumb bit to the symbol value, so this is a NOP.
                     long symbolValue = relocType is IMAGE_REL_BASED_THUMB_BRANCH24
                         ? definedSymbol.Value & ~1L
                         : definedSymbol.Value;
@@ -409,12 +408,8 @@ public virtual void EmitObject(Stream outputFileStream, IReadOnlyCollection<Depe
                 }
 
                 bool isMethod = node is IMethodBodyNode or AssemblyStubNode;
-#if !READYTORUN
                 long thumbBit = _nodeFactory.Target.Architecture == TargetArchitecture.ARM && isMethod ? 1 : 0;
-#else
-                // R2R records the thumb bit in the addend when needed, so we don't have to do it here.
-                long thumbBit = 0;
-#endif
+
                 if (node is WasmTypeNode signature)
                 {
                     RecordMethodSignature(signature);

src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs

@@ -4329,9 +4329,18 @@ private void recordRelocation(void* location, void* locationRW, void* target, Co
                     break;
             }
 
+            RelocType relocType = GetRelocType(fRelocType);
             relocDelta += addlDelta;
 
-            RelocType relocType = GetRelocType(fRelocType);
+            if (_compilation.TypeSystemContext.Target.Architecture == TargetArchitecture.ARM &&
+                relocType == RelocType.IMAGE_REL_BASED_HIGHLOW &&
+                targetBlock == BlockType.Code)
+            {
+                // The ARM JIT reports PCode targets with the Thumb bit set. Method symbols also
+                // carry the Thumb bit, so keep the relocation addend as an offset from the code byte.
+                relocDelta -= _compilation.TypeSystemContext.Target.CodeDelta;
+            }
+
             // relocDelta is stored as the value
             Relocation.WriteValue(relocType, location, relocDelta);
 

src/coreclr/tools/aot/ILCompiler.ReadyToRun.Tests/ILCompiler.ReadyToRun.Tests.csproj

@@ -21,6 +21,7 @@
 
   <ItemGroup>
     <ProjectReference Include="../ILCompiler.Reflection.ReadyToRun/ILCompiler.Reflection.ReadyToRun.csproj" />
+    <ProjectReference Include="../crossgen2/crossgen2_inbuild.csproj" ReferenceOutputAssembly="false" />
   </ItemGroup>
 
   <!-- Test case source files are embedded as resources so we can compile them with Roslyn at test time.

src/coreclr/tools/aot/ILCompiler.ReadyToRun.Tests/TestCases/CrossModuleInlining/ExceptionHandling.cs

@@ -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.
+
+using System;
+using System.Runtime.CompilerServices;
+
+public static class ExceptionHandling
+{
+    public static int CallDependency() => InlineableLib.GetValue() + MethodWithSwitchTable(5);
+
+    public static int MethodWithExceptionInfo(int value)
+    {
+        try
+        {
+            return 100 / value;
+        }
+        catch (DivideByZeroException)
+        {
+            return -1;
+        }
+    }
+
+    public static int MethodWithSwitchTable(int value)
+    {
+        return value switch
+        {
+            0 => Case0(),
+            1 => Case1(),
+            2 => Case2(),
+            3 => Case3(),
+            4 => Case4(),
+            5 => Case5(),
+            6 => Case6(),
+            _ => CaseDefault(),
+        };
+    }
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static int Case0() => 10;
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static int Case1() => 11;
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static int Case2() => 12;
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static int Case3() => 13;
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static int Case4() => 14;
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static int Case5() => 15;
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static int Case6() => 16;
+
+    [MethodImpl(MethodImplOptions.NoInlining)]
+    private static int CaseDefault() => 17;
+}

src/coreclr/tools/aot/ILCompiler.ReadyToRun.Tests/TestCases/R2RTestSuites.cs

@@ -57,6 +57,42 @@ static void Validate(ReadyToRunReader reader)
         }
     }
 
+    [Fact]
+    public void ArmThumbBitRelocationTargets()
+    {
+        var inlineableLib = new CompiledAssembly
+        {
+            AssemblyName = "InlineableLib",
+            SourceResourceNames = ["CrossModuleInlining/Dependencies/InlineableLib.cs"],
+        };
+        var exceptionHandling = new CompiledAssembly
+        {
+            AssemblyName = nameof(ArmThumbBitRelocationTargets),
+            SourceResourceNames = ["CrossModuleInlining/ExceptionHandling.cs"],
+            References = [inlineableLib],
+        };
+
+        new R2RTestRunner(_output).Run(new R2RTestCase(
+            nameof(ArmThumbBitRelocationTargets),
+            [
+                new(nameof(ArmThumbBitRelocationTargets),
+                [
+                    new CrossgenAssembly(exceptionHandling),
+                    new CrossgenAssembly(inlineableLib) { Kind = Crossgen2InputKind.Reference },
+                ])
+                {
+                    Options = [Crossgen2Option.TargetArchArm],
+                    Validate = Validate,
+                },
+            ]));
+
+        static void Validate(ReadyToRunReader reader)
+        {
+            string diag;
+            Assert.True(R2RAssert.HasExpectedArmThumbBitTargets(reader, out diag), diag);
+        }
+    }
+
     [Fact]
     public void TransitiveReferences()
     {

src/coreclr/tools/aot/ILCompiler.ReadyToRun.Tests/TestCasesRunner/R2RDriver.cs

@@ -33,8 +33,7 @@ internal enum Crossgen2Option
     ObjectFormat,
     HotColdSplitting,
     Optimize,
-    TargetArch,
-    TargetOS,
+    TargetArchArm,
 }
 
 internal static class Crossgen2OptionsExtensions
@@ -61,8 +60,7 @@ internal static class Crossgen2OptionsExtensions
         Crossgen2Option.ObjectFormat => $"--object-format",
         Crossgen2Option.HotColdSplitting => $"--hot-cold-splitting",
         Crossgen2Option.Optimize => $"--optimize",
-        Crossgen2Option.TargetArch => $"--target-arch",
-        Crossgen2Option.TargetOS => $"--target-os",
+        Crossgen2Option.TargetArchArm => $"--targetarch:arm",
         _ => throw new ArgumentOutOfRangeException(nameof(kind)),
     };
 }