[NativeAOT/x86] Fix funclet unwinding (#100732)

* Guard ABI changes necessary for funclet unwinding with UsesFunclets()/FEATURE_EH_FUNCLETS instead of UNIX_X86_ABI

* Fix the emitFullArgInfo condition.

* Update comments, add test case

src/coreclr/gcdump/i386/gcdumpx86.cpp

@@ -456,10 +456,10 @@ size_t GCDump::DumpGCTable(PTR_CBYTE table,
  /* non-ptr arg push */
 
  curOffs += (val & 0x07);
-#ifndef UNIX_X86_ABI
- // For x86/Linux, non-ptr arg pushes can be reported even for EBP frames
+#ifndef FEATURE_EH_FUNCLETS
+ // For funclets, non-ptr arg pushes can be reported even for EBP frames
  _ASSERTE(!header.ebpFrame);
-#endif // UNIX_X86_ABI
+#endif // FEATURE_EH_FUNCLETS
  argCnt++;
 
  DumpEncoding(bp, table-bp); bp = table;

src/coreclr/jit/emit.cpp

@@ -6680,11 +6680,11 @@ unsigned emitter::emitEndCodeGen(Compiler* comp,
 
  emitFullyInt = fullyInt;
  emitFullGCinfo = fullPtrMap;
-
-#ifndef UNIX_X86_ABI
- emitFullArgInfo = !emitHasFramePtr;
+#if TARGET_X86
+ // On x86 with funclets we emit full ptr map even for EBP frames
+ emitFullArgInfo = comp->UsesFunclets() ? fullPtrMap : !emitHasFramePtr;
 #else
- emitFullArgInfo = fullPtrMap;
+ emitFullArgInfo = !emitHasFramePtr;
 #endif
 
 #if EMITTER_STATS

src/coreclr/jit/gcencode.cpp

@@ -2584,9 +2584,7 @@ size_t GCInfo::gcMakeRegPtrTable(BYTE* dest, int mask, const InfoHdr& header, un
 
  assert((codeDelta & 0x7) == codeDelta);
  *dest++ = 0xB0 | (BYTE)codeDelta;
-#ifndef UNIX_X86_ABI
- assert(!compiler->isFramePointerUsed());
-#endif
+ assert(compiler->UsesFunclets() || !compiler->isFramePointerUsed());
 
  /* Remember the new 'last' offset */
 

src/coreclr/jit/morph.cpp

@@ -14236,6 +14236,13 @@ void Compiler::fgSetOptions()
  if (info.compXcptnsCount > 0)
  {
  codeGen->setFramePointerRequiredEH(true);
+
+ if (UsesFunclets())
+ {
+ assert(!codeGen->isGCTypeFixed());
+ // Enforce fully interruptible codegen for funclet unwinding
+ SetInterruptible(true);
+ }
  }
 
 #else // !TARGET_X86
@@ -14247,15 +14254,6 @@ void Compiler::fgSetOptions()
 
 #endif // TARGET_X86
 
-#ifdef UNIX_X86_ABI
- if (info.compXcptnsCount > 0)
- {
- assert(!codeGen->isGCTypeFixed());
- // Enforce fully interruptible codegen for funclet unwinding
- SetInterruptible(true);
- }
-#endif // UNIX_X86_ABI
-
  if (compMethodRequiresPInvokeFrame())
  {
  codeGen->setFramePointerRequired(true); // Setup of Pinvoke frame currently requires an EBP style frame

src/coreclr/vm/gc_unwind_x86.inl

@@ -1519,10 +1519,10 @@ unsigned scanArgRegTableI(PTR_CBYTE table,
 
  bool hasPartialArgInfo;
 
-#ifndef UNIX_X86_ABI
+#ifndef FEATURE_EH_FUNCLETS
  hasPartialArgInfo = info->ebpFrame;
 #else
- // For x86/Linux, interruptible code always has full arg info
+ // For funclets, interruptible code always has full arg info
  //
  // This should be aligned with emitFullArgInfo setting at
  // emitter::emitEndCodeGen (in JIT)

src/tests/nativeaot/SmokeTests/Exceptions/Exceptions.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Diagnostics;
+using System.Runtime.CompilerServices;
 using System.Runtime.ExceptionServices;
 using System.Text;
 
@@ -160,6 +161,8 @@ public static int Main()
 
  TestFirstChanceExceptionEvent();
 
+ TestUnwindInFunclet();
+
  throw new Exception("UnhandledException");
 
  return Fail;
@@ -300,5 +303,27 @@ static bool FilterWithGC()
  CreateSomeGarbage();
  return true;
  }
+
+ static void TestUnwindInFunclet()
+ {
+ try
+ {
+ throw new Exception();
+ }
+ catch (Exception e)
+ {
+ // x86 pushes the call arguments on the stack and moves the stack pointer.
+ // We use a non-inlined call with enough parameters to force this to happen,
+ // so we can verify that the unwinder can walk through this funclet. The
+ // unwinding is triggered by the GC.Collect call.
+ MultiparameterCallWithGC(0, 1, 2, 3, 4);
+ }
+ }
+
+ [MethodImpl(MethodImplOptions.NoInlining)]
+ static void MultiparameterCallWithGC(nint a, nint b, nint c, nint d, nint f)
+ {
+ GC.Collect();
+ }
 }