[WebAssembly] Emit .import_global assembler directives

Support a new assembler directive, .import_global, to declare imported
global variables (i.e. those with external linkage and no
initializer). The linker turns these into wasm imports.

Patch by Jacob Gravelle

Differential Revision: https://reviews.llvm.org/D26875

llvm-svn: 288296

1 files changed, 4 insertions, 0 deletions

diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.h b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.h
index cf164ca5924..23ac3190243 100644
--- a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.h
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.h
@@ -45,6 +45,8 @@ public:
   }
   /// .indidx
   virtual void emitIndIdx(const MCExpr *Value) = 0;
+  /// .import_global
+  virtual void emitGlobalImport(StringRef name) = 0;
 };
 
 /// This part is for ascii assembly output
@@ -62,6 +64,7 @@ public:
                                 SmallVectorImpl<MVT> &Params,
                                 SmallVectorImpl<MVT> &Results) override;
   void emitIndIdx(const MCExpr *Value) override;
+  void emitGlobalImport(StringRef name) override;
 };
 
 /// This part is for ELF object output
@@ -77,6 +80,7 @@ public:
                                 SmallVectorImpl<MVT> &Params,
                                 SmallVectorImpl<MVT> &Results) override;
   void emitIndIdx(const MCExpr *Value) override;
+  void emitGlobalImport(StringRef name) override;
 };
 
 } // end namespace llvm