[llvm] 66bfbed - [WebAssembly] Support wasm exports with zero-length names.

[Dan Gohman via llvm-commits]

Author: Dan Gohman
Date: 2020-03-26T16:20:43-07:00
New Revision: 66bfbedbdfb98bb3c8fbda9ee839e46b430122d1

URL: https://github.com/llvm/llvm-project/commit/66bfbedbdfb98bb3c8fbda9ee839e46b430122d1
DIFF: https://github.com/llvm/llvm-project/commit/66bfbedbdfb98bb3c8fbda9ee839e46b430122d1.diff

LOG: [WebAssembly] Support wasm exports with zero-length names.

Zero-length strings are valid export names in WebAssembly, so allow
users to specify them.

Differential Revision: https://reviews.llvm.org/D71793

Added: 
    

Modified: 
    lld/test/wasm/export-name.ll
    lld/wasm/InputChunks.h
    lld/wasm/Writer.cpp
    llvm/include/llvm/BinaryFormat/Wasm.h

Removed: 
    


################################################################################
diff  --git a/lld/test/wasm/export-name.ll b/lld/test/wasm/export-name.ll
index 83a8bd907c79..b02f253760d1 100644
--- a/lld/test/wasm/export-name.ll
+++ b/lld/test/wasm/export-name.ll
@@ -8,6 +8,10 @@ define void @foo() #0 {
     ret void
 }
 
+define void @qux() #1 {
+    ret void
+}
+
 define void @_start() {
     call void @foo()
     ret void
@@ -15,6 +19,8 @@ define void @_start() {
 
 attributes #0 = { "wasm-export-name"="bar" }
 
+attributes #1 = { "wasm-export-name"="" }
+
 ; CHECK:       - Type:            EXPORT
 ; CHECK-NEXT:    Exports:
 ; CHECK-NEXT:      - Name:            memory
@@ -23,6 +29,9 @@ attributes #0 = { "wasm-export-name"="bar" }
 ; CHECK-NEXT:      - Name:            bar
 ; CHECK-NEXT:        Kind:            FUNCTION
 ; CHECK-NEXT:        Index:           0
-; CHECK-NEXT:      - Name:            _start
+; CHECK-NEXT:      - Name:            ''
 ; CHECK-NEXT:        Kind:            FUNCTION
 ; CHECK-NEXT:        Index:           1
+; CHECK-NEXT:      - Name:            _start
+; CHECK-NEXT:        Kind:            FUNCTION
+; CHECK-NEXT:        Index:           2

diff  --git a/lld/wasm/InputChunks.h b/lld/wasm/InputChunks.h
index 030c9a9dd561..cadff6883fa4 100644
--- a/lld/wasm/InputChunks.h
+++ b/lld/wasm/InputChunks.h
@@ -130,8 +130,8 @@ class InputFunction : public InputChunk {
   void writeTo(uint8_t *sectionStart) const override;
   StringRef getName() const override { return function->SymbolName; }
   StringRef getDebugName() const override { return function->DebugName; }
-  StringRef getExportName() const {
-    return function ? function->ExportName : "";
+  llvm::Optional<StringRef> getExportName() const {
+    return function ? function->ExportName : llvm::Optional<StringRef>();
   }
   uint32_t getComdat() const override { return function->Comdat; }
   uint32_t getFunctionInputOffset() const { return getInputSectionOffset(); }

diff  --git a/lld/wasm/Writer.cpp b/lld/wasm/Writer.cpp
index ca0bfef4599e..9f4b6adc48bb 100644
--- a/lld/wasm/Writer.cpp
+++ b/lld/wasm/Writer.cpp
@@ -520,9 +520,8 @@ void Writer::calculateExports() {
     StringRef name = sym->getName();
     WasmExport export_;
     if (auto *f = dyn_cast<DefinedFunction>(sym)) {
-      StringRef exportName = f->function->getExportName();
-      if (!exportName.empty()) {
-        name = exportName;
+      if (Optional<StringRef> exportName = f->function->getExportName()) {
+        name = *exportName;
       }
       export_ = {name, WASM_EXTERNAL_FUNCTION, f->getFunctionIndex()};
     } else if (auto *g = dyn_cast<DefinedGlobal>(sym)) {

diff  --git a/llvm/include/llvm/BinaryFormat/Wasm.h b/llvm/include/llvm/BinaryFormat/Wasm.h
index e39760e59ec2..dd743dbbbefa 100644
--- a/llvm/include/llvm/BinaryFormat/Wasm.h
+++ b/llvm/include/llvm/BinaryFormat/Wasm.h
@@ -132,7 +132,7 @@ struct WasmFunction {
   uint32_t CodeSectionOffset;
   uint32_t Size;
   uint32_t CodeOffset;  // start of Locals and Body
-  StringRef ExportName; // from the "export" section
+  Optional<StringRef> ExportName; // from the "export" section
   StringRef SymbolName; // from the "linking" section
   StringRef DebugName;  // from the "name" section
   uint32_t Comdat;      // from the "comdat info" section