COFF: Emit .pdata/.xdata as associative COMDAT sections/symbols

dotnet · Oct 2, 2023 · 0b30437 · 0b30437
1 parent f402b72
commit 0b30437
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Showing 2 changed files with 31 additions and 7 deletions.
diff --git a/src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/ObjectWriter/CoffObjectWriter.cs b/src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/ObjectWriter/CoffObjectWriter.cs
@@ -195,6 +195,16 @@ protected override void EmitReferencedMethod(string symbolName)
         protected override void EmitSymbolTable()
         {
             var definedSymbols = GetDefinedSymbols();
+            var sectionSymbol = new string[_sections.Count];
+
+            foreach (var (symbolName, symbolDefinition) in definedSymbols)
+            {
+                if (symbolDefinition.Value == 0 &&
+                    sectionSymbol[symbolDefinition.SectionIndex] is null)
+                {
+                    sectionSymbol[symbolDefinition.SectionIndex] = symbolName;
+                }
+            }
 
             int sectionIndex = 0;
             foreach (var (sectionHeader, _, _, comdatName) in _sections)
@@ -239,6 +249,17 @@ protected override void EmitSymbolTable()
                             StorageClass = 2 // IMAGE_SYM_CLASS_EXTERNAL
                         });
                     }
+                    else if (sectionSymbol[sectionIndex] is not null)
+                    {
+                        _symbolNameToIndex.Add(sectionSymbol[sectionIndex], (uint)_symbols.Count);
+                        _symbols.Add(new CoffSymbol
+                        {
+                            Name = sectionSymbol[sectionIndex],
+                            Value = 0,
+                            SectionIndex = (uint)(1 + sectionIndex),
+                            StorageClass = 3 // IMAGE_SYM_CLASS_STATIC
+                        });
+                    }
                 }
                 sectionIndex++;
             }
@@ -378,8 +399,6 @@ protected override void EmitUnwindInfo(
                 Span<byte> tempBuffer = stackalloc byte[4];
                 bool shareSymbol = ShouldShareSymbol((ObjectNode)nodeWithCodeInfo);
 
-                pdataSectionWriter = shareSymbol ? GetOrCreateSection(GetSharedSection(PDataSection, currentSymbolName)) : _pdataSectionWriter;
-
                 for (int i = 0; i < frameInfos.Length; i++)
                 {
                     FrameInfo frameInfo = frameInfos[i];
@@ -397,11 +416,13 @@ protected override void EmitUnwindInfo(
                         // and produces errors about duplicate symbols that point into the
                         // associative section, so we are stuck with one section per each
                         // unwind symbol.
-                        xdataSectionWriter = GetOrCreateSection(GetSharedSection(ObjectNodeSection.XDataSection, unwindSymbolName));
+                        xdataSectionWriter = GetOrCreateSection(GetSharedSection(ObjectNodeSection.XDataSection, currentSymbolName));
+                        pdataSectionWriter = GetOrCreateSection(GetSharedSection(PDataSection, currentSymbolName));
                     }
                     else
                     {
                         xdataSectionWriter = _xdataSectionWriter;
+                        pdataSectionWriter = _pdataSectionWriter;
                     }
 
                     // Need to emit the UNWIND_INFO at 4-byte alignment to ensure that the

diff --git a/src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/ObjectWriter/ObjectWriter.cs b/src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/ObjectWriter/ObjectWriter.cs
@@ -36,7 +36,7 @@ protected sealed record SymbolicRelocation(int Offset, RelocType Type, string Sy
         private byte _insPaddingByte;
 
         // Standard sections
-        private Dictionary<(string, string), int> _sectionNameToSectionIndex = new();
+        private Dictionary<string, int> _sectionNameToSectionIndex = new();
         private List<ObjectWriterStream> _sectionIndexToStream = new();
         private List<List<SymbolicRelocation>> _sectionIndexToRelocations = new();
 
@@ -79,14 +79,17 @@ protected SectionWriter GetOrCreateSection(ObjectNodeSection section)
             int sectionIndex;
             ObjectWriterStream sectionStream;
 
-            if (!_sectionNameToSectionIndex.TryGetValue((section.Name, section.ComdatName), out sectionIndex))
+            if (section.ComdatName is not null || !_sectionNameToSectionIndex.TryGetValue(section.Name, out sectionIndex))
             {
                 sectionStream = new ObjectWriterStream(section.Type == SectionType.Executable ? _insPaddingByte : (byte)0);
                 CreateSection(section, sectionStream);
-                sectionIndex = _sectionNameToSectionIndex.Count;
-                _sectionNameToSectionIndex.Add((section.Name, section.ComdatName), sectionIndex);
+                sectionIndex = _sectionIndexToStream.Count;
                 _sectionIndexToStream.Add(sectionStream);
                 _sectionIndexToRelocations.Add(new());
+                if (section.ComdatName is null)
+                {
+                    _sectionNameToSectionIndex.Add(section.Name, sectionIndex);
+                }
             }
             else
             {