Option to pass alignment hints to the load and store macros

w2c2/c.c

@@ -560,6 +560,7 @@ typedef struct WasmCFunctionWriter {
     bool pretty;
     bool debug;
     bool linkImports;
+    bool writeAlignment;
     WasmDebugLines* debugLines;
 } WasmCFunctionWriter;
 
@@ -1232,6 +1233,10 @@ wasmCWriteLoadExpr(
                 MUST (stringBuilderAppendU32(writer->builder, instruction.offset))
                 MUST (wasmCWrite(writer, "U"))
             }
+            if (writer->writeAlignment) {
+                MUST (wasmCWriteComma(writer))
+                MUST (stringBuilderAppendU32(writer->builder, instruction.align))
+            }
             MUST (wasmCWrite(writer, ");\n"))
 
             wasmTypeStackDrop(writer->typeStack, 1);
@@ -1332,6 +1337,10 @@ wasmCWriteStoreExpr(
                 stackIndex0,
                 writer->typeStack->valueTypes[stackIndex0]
             ))
+            if (writer->writeAlignment) {
+                MUST (wasmCWriteComma(writer))
+                MUST (stringBuilderAppendU32(writer->builder, instruction.align))
+            }
             MUST (wasmCWrite(writer, ");\n"))
 
             wasmTypeStackDrop(writer->typeStack, 2);
@@ -3278,7 +3287,8 @@ wasmCWriteFunctionBody(
     WasmDebugLines* debugLines,
     bool pretty,
     bool debug,
-    bool linkImports
+    bool linkImports,
+    bool writeAlignment
 ) {
     Buffer code = function.code;
     StringBuilder stringBuilder = emptyStringBuilder;
@@ -3317,6 +3327,7 @@ wasmCWriteFunctionBody(
         writer.pretty = pretty;
         writer.debug = debug;
         writer.linkImports = linkImports;
+        writer.writeAlignment = writeAlignment;
         writer.debugLines = debugLines;
 
         MUST (wasmLabelStackPush(writer.labelStack, 0, resultType, &label))
@@ -3446,7 +3457,8 @@ wasmCWriteFunctionImplementations(
     U32 endIndex,
     bool pretty,
     bool debug,
-    bool linkImports
+    bool linkImports,
+    bool writeAlignment
 ) {
     const size_t functionImportCount = module->functionImports.length;
 
@@ -3490,7 +3502,8 @@ wasmCWriteFunctionImplementations(
             debugLines,
             pretty,
             debug,
-            linkImports
+            linkImports,
+            writeAlignment
         ))
         fputs("\n", file);
     }
@@ -4732,7 +4745,8 @@ wasmCWriteImplementationFile(
     U32 startFunctionIndex,
     bool pretty,
     bool debug,
-    bool linkImports
+    bool linkImports,
+    bool writeAlignment
 ) {
     char filename[13];
     U32 functionCount = module->functions.count;
@@ -4773,7 +4787,8 @@ wasmCWriteImplementationFile(
             endFunctionIndex,
             pretty,
             debug,
-            linkImports
+            linkImports,
+            writeAlignment
         ))
     }
 
@@ -4804,6 +4819,7 @@ typedef struct WasmCImplementationWriterTask {
     bool pretty;
     bool debug;
     bool linkImports;
+    bool writeAlignment;
     bool result;
 } WasmCImplementationWriterTask;
 
@@ -4874,6 +4890,7 @@ wasmCImplementationWriterThread(
             bool pretty = task->pretty;
             bool debug = task->debug;
             bool linkImports = task->linkImports;
+            bool writeAlignment = task->writeAlignment;
 
             writer->task = NULL;
 
@@ -4891,7 +4908,8 @@ wasmCImplementationWriterThread(
                     startFunctionIndex,
                     pretty,
                     debug,
-                    linkImports
+                    linkImports,
+                    writeAlignment
                 );
                 if (!result) {
                     fprintf(
@@ -4942,7 +4960,8 @@ wasmCWriteModuleImplementationFiles(
         0,
         options.pretty,
         options.debug,
-        options.linkImports
+        options.linkImports,
+        options.writeAlignment
     ))
 
     {
@@ -4961,6 +4980,7 @@ wasmCWriteModuleImplementationFiles(
         task.pretty = options.pretty;
         task.debug = options.debug;
         task.linkImports = options.linkImports;
+        task.writeAlignment = options.writeAlignment;
 
         for (; jobIndex < threadCount; jobIndex++) {
             int err = pthread_create(
@@ -5012,7 +5032,8 @@ wasmCWriteModuleImplementationFiles(
                 startFunctionIndex,
                 options.pretty,
                 options.debug,
-                options.linkImports
+                options.linkImports,
+                options.writeAlignment
             ))
 #endif /* HAS_PTHREAD */
         }

w2c2/c.h

@@ -11,11 +11,12 @@ typedef struct WasmCWriteModuleOptions {
     bool pretty;
     bool debug;
     bool linkImports;
+    bool writeAlignment;
     WasmDataSegmentMode dataSegmentMode;
 } WasmCWriteModuleOptions;
 
 static const WasmCWriteModuleOptions emptyWasmCWriteModuleOptions ={
-    NULL, 0, 0, false, false, false, wasmDataSegmentModeArrays
+    NULL, 0, 0, false, false, false, false, wasmDataSegmentModeArrays
 };
 
 bool

w2c2/instruction.c

@@ -1,4 +1,5 @@
 #include "instruction.h"
+#include <stdio.h>
 
 /* WasmLocalInstruction */
 
@@ -72,7 +73,7 @@ wasmLoadStoreInstructionRead(
     MUST (leb128ReadU32(buffer, &offset) > 0)
 
     result->opcode = opcode;
-    result->align = align;
+    result->align = 1 << align;
     result->offset = offset;
 
     return true;

w2c2/main.c

@@ -22,9 +22,9 @@
 #include "stringbuilder.h"
 
 #if HAS_PTHREAD
-static char* const optString = "t:f:d:pglh";
+static char* const optString = "t:f:d:pglah";
 #else
-static char* const optString = "f:d:pglh";
+static char* const optString = "f:d:pglah";
 #endif /* HAS_PTHREAD */
 
 static
@@ -94,6 +94,7 @@ main(
     bool pretty = false;
     bool debug = false;
     bool linkImports = false;
+    bool writeAlignment = false;
     WasmDataSegmentMode dataSegmentMode = wasmDataSegmentModeArrays;
     char moduleName[PATH_MAX];
 
@@ -126,6 +127,10 @@ main(
                 linkImports = true;
                 break;
             }
+            case 'a': {
+                writeAlignment = true;
+                break;
+            }
             case 'd': {
                 if (strcmp(optarg, "arrays") == 0) {
                     dataSegmentMode = wasmDataSegmentModeArrays;
@@ -180,6 +185,7 @@ main(
                     "  -g         Generate debug information (function names using asm(); #line directives based on DWARF, if available)\n"
                     "  -p         Generate pretty code\n"
                     "  -l         Link against imported functions rather than resolving them at runtime\n"
+                    "  -a         Pass alignment hints to the load and store macros. You'll need a custom w2c2_base.h to use this\n"
                 );
                 return 0;
             }
@@ -259,6 +265,7 @@ main(
         writeOptions.pretty = pretty;
         writeOptions.debug = debug;
         writeOptions.linkImports = linkImports;
+        writeOptions.writeAlignment = writeAlignment;
         writeOptions.dataSegmentMode = dataSegmentMode;
 
         if (!wasmCWriteModule(reader.module, moduleName, writeOptions)) {