[lld] r370010 - [lld][WebAssembly] Store table base in config rather than passing it around. NFC.

[Sam Clegg via llvm-commits]

Author: sbc
Date: Mon Aug 26 21:19:34 2019
New Revision: 370010

URL: http://llvm.org/viewvc/llvm-project?rev=370010&view=rev
Log:
[lld][WebAssembly] Store table base in config rather than passing it around. NFC.

I've got another change that makes more use of this value in other
places.

Differential Revision: https://reviews.llvm.org/D66777

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

Modified: lld/trunk/wasm/Config.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/wasm/Config.h?rev=370010&r1=370009&r2=370010&view=diff
==============================================================================
--- lld/trunk/wasm/Config.h (original)
+++ lld/trunk/wasm/Config.h Mon Aug 26 21:19:34 2019
@@ -70,6 +70,12 @@ struct Configuration {
 
   // True if we are creating position-independent code.
   bool isPic;
+
+  // The table offset at which to place function addresses.  We reserve zero
+  // for the null function pointer.  This gets set to 1 for exectuables and 0
+  // for shared libraries (since they always added to a dynamic offset at
+  // runtime).
+  uint32_t tableBase = 0;
 };
 
 // The only instance of Configuration struct.

Modified: lld/trunk/wasm/SyntheticSections.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/wasm/SyntheticSections.cpp?rev=370010&r1=370009&r2=370010&view=diff
==============================================================================
--- lld/trunk/wasm/SyntheticSections.cpp (original)
+++ lld/trunk/wasm/SyntheticSections.cpp Mon Aug 26 21:19:34 2019
@@ -143,7 +143,7 @@ void ImportSection::writeBody() {
   }
 
   if (config->importTable) {
-    uint32_t tableSize = out.elemSec->elemOffset + out.elemSec->numEntries();
+    uint32_t tableSize = config->tableBase + out.elemSec->numEntries();
     WasmImport import;
     import.Module = defaultModule;
     import.Field = functionTableName;
@@ -212,7 +212,7 @@ void FunctionSection::addFunction(InputF
 }
 
 void TableSection::writeBody() {
-  uint32_t tableSize = out.elemSec->elemOffset + out.elemSec->numEntries();
+  uint32_t tableSize = config->tableBase + out.elemSec->numEntries();
 
   raw_ostream &os = bodyOutputStream;
   writeUleb128(os, 1, "table count");
@@ -313,7 +313,7 @@ void ExportSection::writeBody() {
 void ElemSection::addEntry(FunctionSymbol *sym) {
   if (sym->hasTableIndex())
     return;
-  sym->setTableIndex(elemOffset + indirectFunctions.size());
+  sym->setTableIndex(config->tableBase + indirectFunctions.size());
   indirectFunctions.emplace_back(sym);
 }
 
@@ -328,12 +328,12 @@ void ElemSection::writeBody() {
     initExpr.Value.Global = WasmSym::tableBase->getGlobalIndex();
   } else {
     initExpr.Opcode = WASM_OPCODE_I32_CONST;
-    initExpr.Value.Int32 = elemOffset;
+    initExpr.Value.Int32 = config->tableBase;
   }
   writeInitExpr(os, initExpr);
   writeUleb128(os, indirectFunctions.size(), "elem count");
 
-  uint32_t tableIndex = elemOffset;
+  uint32_t tableIndex = config->tableBase;
   for (const FunctionSymbol *sym : indirectFunctions) {
     assert(sym->getTableIndex() == tableIndex);
     writeUleb128(os, sym->getFunctionIndex(), "function index");

Modified: lld/trunk/wasm/SyntheticSections.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/wasm/SyntheticSections.h?rev=370010&r1=370009&r2=370010&view=diff
==============================================================================
--- lld/trunk/wasm/SyntheticSections.h (original)
+++ lld/trunk/wasm/SyntheticSections.h Mon Aug 26 21:19:34 2019
@@ -219,13 +219,12 @@ public:
 
 class ElemSection : public SyntheticSection {
 public:
-  ElemSection(uint32_t offset)
-      : SyntheticSection(llvm::wasm::WASM_SEC_ELEM), elemOffset(offset) {}
+  ElemSection()
+      : SyntheticSection(llvm::wasm::WASM_SEC_ELEM) {}
   bool isNeeded() const override { return indirectFunctions.size() > 0; };
   void writeBody() override;
   void addEntry(FunctionSymbol *sym);
   uint32_t numEntries() const { return indirectFunctions.size(); }
-  uint32_t elemOffset;
 
 protected:
   std::vector<const FunctionSymbol *> indirectFunctions;

Modified: lld/trunk/wasm/Writer.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/wasm/Writer.cpp?rev=370010&r1=370009&r2=370010&view=diff
==============================================================================
--- lld/trunk/wasm/Writer.cpp (original)
+++ lld/trunk/wasm/Writer.cpp Mon Aug 26 21:19:34 2019
@@ -87,7 +87,6 @@ private:
   void writeSections();
 
   uint64_t fileSize = 0;
-  uint32_t tableBase = 0;
 
   std::vector<WasmInitEntry> initFunctions;
   llvm::StringMap<std::vector<InputSection *>> customSectionMapping;
@@ -852,7 +851,7 @@ void Writer::createSyntheticSections() {
   out.globalSec = make<GlobalSection>();
   out.eventSec = make<EventSection>();
   out.exportSec = make<ExportSection>();
-  out.elemSec = make<ElemSection>(tableBase);
+  out.elemSec = make<ElemSection>();
   out.dataCountSec = make<DataCountSection>(segments.size());
   out.linkingSec = make<LinkingSection>(initFunctions, segments);
   out.nameSec = make<NameSection>();
@@ -867,9 +866,9 @@ void Writer::run() {
   // For PIC code the table base is assigned dynamically by the loader.
   // For non-PIC, we start at 1 so that accessing table index 0 always traps.
   if (!config->isPic) {
-    tableBase = 1;
+    config->tableBase = 1;
     if (WasmSym::definedTableBase)
-      WasmSym::definedTableBase->setVirtualAddress(tableBase);
+      WasmSym::definedTableBase->setVirtualAddress(config->tableBase);
   }
 
   log("-- createOutputSegments");