[lld] r361470 - [WebAssembly] Seal imports section before counting imports

Sam Clegg via llvm-commits llvm-commits at lists.llvm.org
Thu May 23 02:41:03 PDT 2019


Author: sbc
Date: Thu May 23 02:41:03 2019
New Revision: 361470

URL: http://llvm.org/viewvc/llvm-project?rev=361470&view=rev
Log:
[WebAssembly] Seal imports section before counting imports

Summary:
Before we can assign entries in the function of global index space
we need to know the total number of function and global imports
respectively.

To avoid programmer error this change seals that imports section before
assigned function and global index space.  Any attempt to add an import
after the section is sealed will assert.

The lack this such as check caused  https://reviews.llvm.org/D61876
to be reverted.  I'm also trying to craft a test case the this
failure.

Subscribers: dschuff, jgravelle-google, aheejin, sunfish, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D62240

Modified:
    lld/trunk/wasm/SyntheticSections.cpp
    lld/trunk/wasm/SyntheticSections.h
    lld/trunk/wasm/Writer.cpp

Modified: lld/trunk/wasm/SyntheticSections.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/wasm/SyntheticSections.cpp?rev=361470&r1=361469&r2=361470&view=diff
==============================================================================
--- lld/trunk/wasm/SyntheticSections.cpp (original)
+++ lld/trunk/wasm/SyntheticSections.cpp Thu May 23 02:41:03 2019
@@ -92,6 +92,7 @@ void TypeSection::writeBody() {
 }
 
 uint32_t ImportSection::numImports() const {
+  assert(IsSealed);
   uint32_t NumImports = ImportedSymbols.size() + GOTSymbols.size();
   if (Config->ImportMemory)
     ++NumImports;
@@ -101,6 +102,7 @@ uint32_t ImportSection::numImports() con
 }
 
 void ImportSection::addGOTEntry(Symbol *Sym) {
+  assert(!IsSealed);
   if (Sym->hasGOTIndex())
     return;
   Sym->setGOTIndex(NumImportedGlobals++);
@@ -108,6 +110,7 @@ void ImportSection::addGOTEntry(Symbol *
 }
 
 void ImportSection::addImport(Symbol *Sym) {
+  assert(!IsSealed);
   ImportedSymbols.emplace_back(Sym);
   if (auto *F = dyn_cast<FunctionSymbol>(Sym))
     F->setFunctionIndex(NumImportedFunctions++);
@@ -202,7 +205,7 @@ void FunctionSection::addFunction(InputF
   if (!Func->Live)
     return;
   uint32_t FunctionIndex =
-      Out.ImportSec->NumImportedFunctions + InputFunctions.size();
+      Out.ImportSec->numImportedFunctions() + InputFunctions.size();
   InputFunctions.emplace_back(Func);
   Func->setFunctionIndex(FunctionIndex);
 }
@@ -251,7 +254,7 @@ void GlobalSection::addGlobal(InputGloba
   if (!Global->Live)
     return;
   uint32_t GlobalIndex =
-      Out.ImportSec->NumImportedGlobals + InputGlobals.size();
+      Out.ImportSec->numImportedGlobals() + InputGlobals.size();
   LLVM_DEBUG(dbgs() << "addGlobal: " << GlobalIndex << "\n");
   Global->setGlobalIndex(GlobalIndex);
   Out.GlobalSec->InputGlobals.push_back(Global);
@@ -270,7 +273,7 @@ void EventSection::writeBody() {
 void EventSection::addEvent(InputEvent *Event) {
   if (!Event->Live)
     return;
-  uint32_t EventIndex = Out.ImportSec->NumImportedEvents + InputEvents.size();
+  uint32_t EventIndex = Out.ImportSec->numImportedEvents() + InputEvents.size();
   LLVM_DEBUG(dbgs() << "addEvent: " << EventIndex << "\n");
   Event->setEventIndex(EventIndex);
   InputEvents.push_back(Event);
@@ -457,7 +460,7 @@ void LinkingSection::addToSymtab(Symbol
 }
 
 unsigned NameSection::numNames() const {
-  unsigned NumNames = Out.ImportSec->NumImportedFunctions;
+  unsigned NumNames = Out.ImportSec->numImportedFunctions();
   for (const InputFunction *F : Out.FunctionSec->InputFunctions)
     if (!F->getName().empty() || !F->getDebugName().empty())
       ++NumNames;

Modified: lld/trunk/wasm/SyntheticSections.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/wasm/SyntheticSections.h?rev=361470&r1=361469&r2=361470&view=diff
==============================================================================
--- lld/trunk/wasm/SyntheticSections.h (original)
+++ lld/trunk/wasm/SyntheticSections.h Thu May 23 02:41:03 2019
@@ -101,14 +101,28 @@ public:
   void writeBody() override;
   void addImport(Symbol *Sym);
   void addGOTEntry(Symbol *Sym);
+  void seal() { IsSealed = true; }
   uint32_t numImports() const;
+  uint32_t numImportedGlobals() const {
+    assert(IsSealed);
+    return NumImportedGlobals;
+  }
+  uint32_t numImportedFunctions() const {
+    assert(IsSealed);
+    return NumImportedFunctions;
+  }
+  uint32_t numImportedEvents() const {
+    assert(IsSealed);
+    return NumImportedEvents;
+  }
 
-  unsigned NumImportedGlobals = 0;
-  unsigned NumImportedFunctions = 0;
-  unsigned NumImportedEvents = 0;
   std::vector<const Symbol *> ImportedSymbols;
 
 protected:
+  bool IsSealed = false;
+  unsigned NumImportedGlobals = 0;
+  unsigned NumImportedFunctions = 0;
+  unsigned NumImportedEvents = 0;
   std::vector<const Symbol *> GOTSymbols;
 };
 

Modified: lld/trunk/wasm/Writer.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/wasm/Writer.cpp?rev=361470&r1=361469&r2=361470&view=diff
==============================================================================
--- lld/trunk/wasm/Writer.cpp (original)
+++ lld/trunk/wasm/Writer.cpp Thu May 23 02:41:03 2019
@@ -439,7 +439,7 @@ void Writer::calculateExports() {
         WasmExport{FunctionTableName, WASM_EXTERNAL_TABLE, 0});
 
   unsigned FakeGlobalIndex =
-      Out.ImportSec->NumImportedGlobals + Out.GlobalSec->InputGlobals.size();
+      Out.ImportSec->numImportedGlobals() + Out.GlobalSec->InputGlobals.size();
 
   for (Symbol *Sym : Symtab->getSymbols()) {
     if (!Sym->isExported())
@@ -532,7 +532,9 @@ static void scanRelocations() {
 }
 
 void Writer::assignIndexes() {
-  assert(Out.FunctionSec->InputFunctions.empty());
+  // Seal the import section, since other index spaces such as function and
+  // global are effected by the number of imports.
+  Out.ImportSec->seal();
 
   for (InputFunction *Func : Symtab->SyntheticFunctions)
     Out.FunctionSec->addFunction(Func);
@@ -543,8 +545,6 @@ void Writer::assignIndexes() {
       Out.FunctionSec->addFunction(Func);
   }
 
-  scanRelocations();
-
   for (InputGlobal *Global : Symtab->SyntheticGlobals)
     Out.GlobalSec->addGlobal(Global);
 
@@ -724,6 +724,8 @@ void Writer::run() {
   populateTargetFeatures();
   log("-- calculateImports");
   calculateImports();
+  log("-- scanRelocations");
+  scanRelocations();
   log("-- assignIndexes");
   assignIndexes();
   log("-- calculateInitFunctions");
@@ -750,9 +752,9 @@ void Writer::run() {
     log("Defined Functions: " + Twine(Out.FunctionSec->InputFunctions.size()));
     log("Defined Globals  : " + Twine(Out.GlobalSec->InputGlobals.size()));
     log("Defined Events   : " + Twine(Out.EventSec->InputEvents.size()));
-    log("Function Imports : " + Twine(Out.ImportSec->NumImportedFunctions));
-    log("Global Imports   : " + Twine(Out.ImportSec->NumImportedGlobals));
-    log("Event Imports    : " + Twine(Out.ImportSec->NumImportedEvents));
+    log("Function Imports : " + Twine(Out.ImportSec->numImportedFunctions()));
+    log("Global Imports   : " + Twine(Out.ImportSec->numImportedGlobals()));
+    log("Event Imports    : " + Twine(Out.ImportSec->numImportedEvents()));
     for (ObjFile *File : Symtab->ObjectFiles)
       File->dumpInfo();
   }




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