[NativeAOT/x86] Implement GetConservativeUpperBoundForOutgoingArgs (#99726)

Author: filipnavara

src/coreclr/nativeaot/Runtime/windows/CoffNativeCodeManager.cpp

@@ -573,9 +573,24 @@ uintptr_t CoffNativeCodeManager::GetConservativeUpperBoundForOutgoingArgs(Method
 
         upperBound = dac_cast<TADDR>(context.Sp);
 #else
-        PORTABILITY_ASSERT("GetConservativeUpperBoundForOutgoingArgs");
-        upperBound = NULL;
-        RhFailFast();
+        PTR_uint8_t gcInfo;
+        uint32_t codeOffset = GetCodeOffset(pMethodInfo, (PTR_VOID)pRegisterSet->IP, &gcInfo);
+
+        hdrInfo infoBuf;
+        size_t infoSize = DecodeGCHdrInfo(GCInfoToken(gcInfo), codeOffset, &infoBuf);
+        PTR_CBYTE table = gcInfo + infoSize;
+
+        REGDISPLAY registerSet = *pRegisterSet;
+
+        ::UnwindStackFrameX86(&registerSet,
+                              (PTR_CBYTE)(m_moduleBase + pNativeMethodInfo->mainRuntimeFunction->BeginAddress),
+                              codeOffset,
+                              &infoBuf,
+                              table,
+                              (PTR_CBYTE)(m_moduleBase + pNativeMethodInfo->runtimeFunction->BeginAddress),
+                              (unwindBlockFlags & UBF_FUNC_KIND_MASK) != UBF_FUNC_KIND_ROOT,
+                              true);
+        upperBound = dac_cast<TADDR>(registerSet.PCTAddr);
 #endif
     }
     return upperBound;