support fixed (non-relocatable) segments in wasm-merge. also a few printing fixes for multiple segments, which we never really printed that prettily (#1316)

Author: kripken

src/passes/Print.cpp

@@ -741,20 +741,18 @@ struct PrintSExpression : public Visitor<PrintSExpression> {
       printTableHeader(curr);
       o << maybeNewLine;
     }
-    if (curr->segments.empty()) return;
-    doIndent(o, indent);
     for (auto& segment : curr->segments) {
       // Don't print empty segments
       if (segment.data.empty()) continue;
+      doIndent(o, indent);
       printOpening(o, "elem ", true);
       visit(segment.offset);
       for (auto name : segment.data) {
         o << ' ';
         printName(name);
       }
-      o << ')';
+      o << ")\n";
     }
-    o << maybeNewLine;
   }
   void printMemoryHeader(Memory* curr) {
     printOpening(o, "memory") << ' ';

src/support/name.h

@@ -40,8 +40,11 @@ struct Name : public cashew::IString {
   Name(const std::string& str) : cashew::IString(str.c_str(), false) {}
 
   friend std::ostream& operator<<(std::ostream& o, Name name) {
-    assert(name.str);
-    return o << '$' << name.str; // reference interpreter requires we prefix all names
+    if (name.str) {
+      return o << '$' << name.str; // reference interpreter requires we prefix all names
+    } else {
+      return o << "(null Name)";
+    }
   }
 
   static Name fromInt(size_t i) {

src/tools/wasm-merge.cpp

@@ -123,13 +123,28 @@ struct Mergeable {
       memoryBaseGlobals.insert(name);
     });
     if (memoryBaseGlobals.size() == 0) {
-      Fatal() << "no memory base was imported";
+      // add one
+      auto* import = new Import;
+      import->name = MEMORY_BASE;
+      import->module = ENV;
+      import->base = MEMORY_BASE;
+      import->kind = ExternalKind::Global;
+      import->globalType = i32;
+      wasm.addImport(import);
+      memoryBaseGlobals.insert(import->name);
     }
     findImportsByBase(wasm, TABLE_BASE, [&](Name name) {
       tableBaseGlobals.insert(name);
     });
     if (tableBaseGlobals.size() == 0) {
-      Fatal() << "no table base was imported";
+      auto* import = new Import;
+      import->name = TABLE_BASE;
+      import->module = ENV;
+      import->base = TABLE_BASE;
+      import->kind = ExternalKind::Global;
+      import->globalType = i32;
+      wasm.addImport(import);
+      tableBaseGlobals.insert(import->name);
     }
   }
 
@@ -169,7 +184,8 @@ struct Mergeable {
   // ensure a relocatable segment exists, of the proper size, including
   // the dylink bump applied into it, standardized into the form of
   // not using a dylink section and instead having enough zeros at
-  // the end. this makes linking much simpler.
+  // the end. this makes linking much simpler.ta
+  // there may be other non-relocatable segments too.
   template<typename T, typename U, typename Segment>
   void standardizeSegment(Module& wasm, T& what, Index size, U zero, Name globalName) {
     Segment* relocatable = nullptr;
@@ -194,9 +210,10 @@ struct Mergeable {
     ensureSize(what, relocatable->data.size());
   }
 
-  // copies a relocatable segment from the input to the output
+  // copies a relocatable segment from the input to the output, and
+  // copies the non-relocatable ones as well
   template<typename T, typename V>
-  void copySegment(T& output, T& input, V updater) {
+  void copySegments(T& output, T& input, V updater) {
     for (auto& inputSegment : input.segments) {
       Expression* inputOffset = inputSegment.offset;
       if (inputOffset->is<GetGlobal>()) {
@@ -213,6 +230,9 @@ struct Mergeable {
           }
         }
         WASM_UNREACHABLE(); // we must find a relocatable one in the output, as we standardized
+      } else {
+        // this is a non-relocatable one. just copy it.
+        output.segments.push_back(inputSegment);
       }
     }
   }
@@ -405,8 +425,8 @@ struct InputMergeable : public ExpressionStackWalker<InputMergeable, Visitor<Inp
     }
 
     // memory&table: we place the new memory segments at a higher position. after the existing ones.
-    copySegment(outputMergeable.wasm.memory, wasm.memory, [](char x) -> char { return x; });
-    copySegment(outputMergeable.wasm.table, wasm.table, [&](Name x) -> Name { return fNames[x]; });
+    copySegments(outputMergeable.wasm.memory, wasm.memory, [](char x) -> char { return x; });
+    copySegments(outputMergeable.wasm.table, wasm.table, [&](Name x) -> Name { return fNames[x]; });
 
     // update the new contents about to be merged in
     walkModule(&wasm);

test/merge/dylib.wasm.combined

@@ -18,7 +18,6 @@
  (global $global$2 i32 (i32.const 0))
  (global $global$0$0 (mut i32) (i32.const 0))
  (global $global$1$0 (mut i32) (i32.const 0))
- 
  (data (get_global $import$0) "hello, world!\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00")
  (export "__post_instantiate" (func $__post_instantiate))
  (export "_main" (func $_main))

test/merge/dylib.wasm.combined.finalized

@@ -18,7 +18,6 @@
  (global $global$2 i32 (i32.const 0))
  (global $global$0$0 (mut i32) (i32.const 0))
  (global $global$1$0 (mut i32) (i32.const 0))
- 
  (data (i32.const 1024) "hello, world!\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00")
  (export "__post_instantiate" (func $__post_instantiate))
  (export "_main" (func $_main))

test/merge/dylib.wasm.combined.finalized.opt

@@ -10,7 +10,6 @@
  (global $global$2 i32 (i32.const 0))
  (global $global$0$0 (mut i32) (i32.const 0))
  (global $global$1$0 (mut i32) (i32.const 0))
- 
  (data (i32.const 1024) "hello, world!")
  (export "__post_instantiate" (func $__post_instantiate))
  (export "_main" (func $_main))

test/merge/dylib.wasm.combined.opt

@@ -13,7 +13,6 @@
  (global $global$2 i32 (i32.const 0))
  (global $global$0$0 (mut i32) (i32.const 0))
  (global $global$1$0 (mut i32) (i32.const 0))
- 
  (data (get_global $import$0) "hello, world!")
  (export "__post_instantiate" (func $__post_instantiate))
  (export "_main" (func $_main))

test/merge/fusing.wast.combined

@@ -9,7 +9,6 @@
  (import "env" "tableBase" (global $tableBase$0 i32))
  (global $a-global i32 (i32.const 0))
  (global $b-global f64 (f64.const 2.14281428))
- 
  (data (get_global $memoryBase) "")
  (export "foo" (func $foo-func))
  (export "aglobal" (global $a-global))

test/merge/fusing.wast.combined.finalized

@@ -9,7 +9,6 @@
  (import "env" "tableBase" (global $tableBase$0 i32))
  (global $a-global i32 (i32.const 0))
  (global $b-global f64 (f64.const 2.14281428))
- 
  (data (i32.const 1024) "")
  (export "foo" (func $foo-func))
  (export "aglobal" (global $a-global))

test/merge/fusing.wast.combined.finalized.opt

@@ -4,7 +4,6 @@
  (import "env" "table" (table 8 anyfunc))
  (global $a-global i32 (i32.const 0))
  (global $b-global f64 (f64.const 2.14281428))
- 
  (export "foo" (func $foo-func))
  (export "aglobal" (global $a-global))
  (export "bar" (func $bar-func))