[PATCH] D42752: [WebAssembly] Add LLVM stub support for defined globals

[Nicholas Wilson via Phabricator via llvm-commits]

ncw created this revision.
ncw added a reviewer: sbc100.
Herald added subscribers: llvm-commits, sunfish, aheejin, jgravelle-google, dschuff, jfb.

It's not much use yet, but getting the constants into the headers and adding some stub support enables at least LLD to be tested against defined & undefined globals.

Comes after https://reviews.llvm.org/D42495. Doesn't break LLD.


Repository:
  rL LLVM

https://reviews.llvm.org/D42752

Files:
  include/llvm/BinaryFormat/Wasm.h
  lib/MC/WasmObjectWriter.cpp
  lib/Object/WasmObjectFile.cpp
  lib/ObjectYAML/WasmYAML.cpp
  tools/obj2yaml/wasm2yaml.cpp


Index: tools/obj2yaml/wasm2yaml.cpp
===================================================================
--- tools/obj2yaml/wasm2yaml.cpp
+++ tools/obj2yaml/wasm2yaml.cpp
@@ -74,6 +74,13 @@
                 WasmYAML::ComdatEntry{wasm::WASM_COMDAT_FUNCTION, Func.Index});
       }
     }
+    for (auto &G : Obj.globals()) {
+      if (!G.Comdat.empty()) {
+        auto &Comdat = LinkingSec->Comdats[ComdatIndexes[G.Comdat]];
+        Comdat.Entries.emplace_back(
+                WasmYAML::ComdatEntry{wasm::WASM_COMDAT_GLOBAL, G.Index});
+      }
+    }
     uint32_t SegmentIndex = 0;
     for (const object::WasmSegment &Segment : Obj.dataSegments()) {
       if (!Segment.Data.Name.empty()) {
Index: lib/ObjectYAML/WasmYAML.cpp
===================================================================
--- lib/ObjectYAML/WasmYAML.cpp
+++ lib/ObjectYAML/WasmYAML.cpp
@@ -374,6 +374,7 @@
 #define ECase(X) IO.enumCase(Kind, #X, wasm::WASM_COMDAT_##X);
   ECase(FUNCTION);
   ECase(DATA);
+  ECase(GLOBAL);
 #undef ECase
 }
 
Index: lib/Object/WasmObjectFile.cpp
===================================================================
--- lib/Object/WasmObjectFile.cpp
+++ lib/Object/WasmObjectFile.cpp
@@ -535,6 +535,15 @@
                                                 object_error::parse_failed);
         getDefinedFunction(Index).Comdat = Name;
         break;
+      case wasm::WASM_COMDAT_GLOBAL:
+        if (!isDefinedGlobalIndex(Index))
+          return make_error<GenericBinaryError>("COMDAT global index out of range",
+                                                object_error::parse_failed);
+        if (!getDefinedGlobal(Index).Comdat.empty())
+          return make_error<GenericBinaryError>("Global in two COMDATs",
+                                                object_error::parse_failed);
+        getDefinedGlobal(Index).Comdat = Name;
+        break;
       }
     }
   }
Index: lib/MC/WasmObjectWriter.cpp
===================================================================
--- lib/MC/WasmObjectWriter.cpp
+++ lib/MC/WasmObjectWriter.cpp
@@ -1209,7 +1209,22 @@
       // A "true" Wasm global (currently just __stack_pointer)
       unsigned WasmIndex;
       if (WS.isDefined()) {
-        report_fatal_error("don't yet support defined globals");
+        // A definition. Write out the Global definition.
+        WasmIndex = NumGlobalImports + Globals.size();
+        WasmGlobal G;
+        G.Type = WS.getGlobalType();
+        // TODO G.InitialValue should come from somewhere, maybe the MCSymbol.
+        // This code is waiting to be used though; I expect thread-local-storage
+        // will want to declare Wasm globals.
+        G.InitialValue = 0;
+        WasmIndices[&WS] = WasmIndex;
+        Globals.push_back(G);
+
+        auto &Section = static_cast<MCSectionWasm &>(WS.getSection());
+        if (const MCSymbolWasm *C = Section.getGroup()) {
+          Comdats[C->getName()].emplace_back(
+              WasmComdatEntry{wasm::WASM_COMDAT_GLOBAL, WasmIndex});
+        }
       } else {
         // An import; the index was assigned above
         WasmIndex = WasmIndices.find(&WS)->second;
Index: include/llvm/BinaryFormat/Wasm.h
===================================================================
--- include/llvm/BinaryFormat/Wasm.h
+++ include/llvm/BinaryFormat/Wasm.h
@@ -74,6 +74,7 @@
   uint32_t Index;
   WasmGlobalType Type;
   WasmInitExpr InitExpr;
+  StringRef Comdat; // from the "comdat info" section
 };
 
 struct WasmImport {
@@ -224,6 +225,7 @@
 enum : unsigned {
   WASM_COMDAT_DATA        = 0x0,
   WASM_COMDAT_FUNCTION    = 0x1,
+  WASM_COMDAT_GLOBAL      = 0x2,
 };
 
 // Kind codes used in the custom "linking" section in the WASM_SYMBOL_TABLE


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