Wasm: emit simple DW_TAG_subprogram DIEs (however, no success with debuggers).

core/src/main/java/org/teavm/backend/wasm/dwarf/DwarfConstants.java

@@ -21,6 +21,7 @@ public final class DwarfConstants {
     public static final int DW_UT_COMPILE = 0x01;
 
     public static final int DW_TAG_COMPILE_UNIT = 0x11;
+    public static final int DW_TAG_SUBPROGRAM = 0x2E;
 
     public static final int DW_AT_NAME = 0x03;
     public static final int DW_AT_STMT_LIST = 0x10;

core/src/main/java/org/teavm/backend/wasm/dwarf/blob/BlobReader.java

@@ -48,7 +48,7 @@ public class BlobReader {
         var offsetInChunk = this.offsetInChunk;
         while (ptr < to) {
             var chunk = blob.chunkAt(currentChunk);
-            var limit = Math.min(ptr + chunk.length, to);
+            var limit = Math.min(ptr + chunk.length - offsetInChunk, to);
             var bytesToWrite = limit - ptr;
             consumer.accept(chunk, offsetInChunk, offsetInChunk + bytesToWrite);
             offsetInChunk += bytesToWrite;

core/src/main/java/org/teavm/backend/wasm/generate/DwarfGenerator.java

@@ -30,7 +30,7 @@ import org.teavm.backend.wasm.model.WasmCustomSection;
 public class DwarfGenerator {
     private DwarfInfoWriter infoWriter = new DwarfInfoWriter();
     private DwarfPlaceholder endOfSection;
-    private DwarfStrings strings = new DwarfStrings();
+    public final DwarfStrings strings = new DwarfStrings();
     private DwarfStrings lineStrings = new DwarfStrings();
     private DwarfLinesGenerator lines = new DwarfLinesGenerator(lineStrings);
     private Marker highPcMarker;
@@ -89,8 +89,10 @@ public class DwarfGenerator {
     }
 
     public void setCodeSize(int codeSize) {
+        var backup = infoWriter.marker();
         highPcMarker.rewind();
         infoWriter.writeInt(codeSize);
+        backup.rewind();
     }
 
     public Collection<? extends WasmCustomSection> createSections() {
@@ -119,4 +121,8 @@ public class DwarfGenerator {
     public void lineNumber(int address, String fileName, int lineNumber) {
         lines.lineNumber(address, fileName, lineNumber);
     }
+
+    public DwarfInfoWriter getInfoWriter() {
+        return infoWriter;
+    }
 }

core/src/main/java/org/teavm/backend/wasm/generate/DwarfStrings.java

@@ -20,11 +20,11 @@ import com.carrotsearch.hppc.ObjectIntMap;
 import java.nio.charset.StandardCharsets;
 import org.teavm.backend.wasm.dwarf.blob.Blob;
 
-class DwarfStrings {
+public class DwarfStrings {
     final Blob blob = new Blob();
     private ObjectIntMap<String> offsets = new ObjectIntHashMap<>();
 
-    int stringRef(String s) {
+    public int stringRef(String s) {
         int ptr = offsets.getOrDefault(s, -1);
         if (ptr < 0) {
             ptr = blob.size();

core/src/main/java/org/teavm/backend/wasm/render/WasmBinaryRenderer.java

@@ -15,6 +15,7 @@
  */
 package org.teavm.backend.wasm.render;
 
+import static org.teavm.backend.wasm.dwarf.DwarfConstants.DW_TAG_SUBPROGRAM;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
@@ -23,6 +24,9 @@ import java.util.List;
 import java.util.Map;
 import java.util.function.Supplier;
 import java.util.stream.Collectors;
+import org.teavm.backend.wasm.dwarf.DwarfAbbreviation;
+import org.teavm.backend.wasm.dwarf.DwarfConstants;
+import org.teavm.backend.wasm.dwarf.DwarfInfoWriter;
 import org.teavm.backend.wasm.generate.DwarfGenerator;
 import org.teavm.backend.wasm.model.WasmCustomSection;
 import org.teavm.backend.wasm.model.WasmFunction;
@@ -55,6 +59,8 @@ public class WasmBinaryRenderer {
     private Map<String, Integer> functionIndexes = new HashMap<>();
     private boolean obfuscated;
     private DwarfGenerator dwarfGenerator;
+    private DwarfInfoWriter infoWriter;
+    private DwarfAbbreviation methodAbbrev;
 
     public WasmBinaryRenderer(WasmBinaryWriter output, WasmBinaryVersion version, boolean obfuscated,
             DwarfGenerator dwarfGenerator) {
@@ -62,6 +68,7 @@ public class WasmBinaryRenderer {
         this.version = version;
         this.obfuscated = obfuscated;
         this.dwarfGenerator = dwarfGenerator;
+        infoWriter = dwarfGenerator != null ? dwarfGenerator.getInfoWriter() : null;
     }
 
     public void render(WasmModule module) {
@@ -317,9 +324,28 @@ public class WasmBinaryRenderer {
         }
         code.writeByte(0x0B);
 
+        if (dwarfGenerator != null && function.getName() != null) {
+            infoWriter.tag(getMethodAbbrev());
+            infoWriter.writeInt(dwarfGenerator.strings.stringRef(function.getName()));
+            infoWriter.writeInt(offset);
+            infoWriter.writeInt(offset + code.getPosition());
+            infoWriter.emptyTag();
+        }
+
         return code.getData();
     }
 
+    private DwarfAbbreviation getMethodAbbrev() {
+        if (methodAbbrev == null) {
+            methodAbbrev = infoWriter.abbreviation(DW_TAG_SUBPROGRAM, true, data -> {
+                data.writeLEB(DwarfConstants.DW_AT_NAME).writeLEB(DwarfConstants.DW_FORM_STRP);
+                data.writeLEB(DwarfConstants.DW_AT_LOW_PC).writeLEB(DwarfConstants.DW_FORM_ADDR);
+                data.writeLEB(DwarfConstants.DW_AT_HIGH_PC).writeLEB(DwarfConstants.DW_FORM_ADDR);
+            });
+        }
+        return methodAbbrev;
+    }
+
     private void renderInitializer(WasmBinaryWriter output, int value) {
         output.writeByte(0x41);
         output.writeLEB(value);