From: Derek Schuff <dschuff@google.com>
Date: Thu, 1 Dec 2016 00:11:15 +0000 (+0000)
Subject: [WebAssembly] Emit .import_global assembler directives
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=a95cded1a3fcecc1aa8ba8ddfc241b9e7ab6a17a;p=llvm

[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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@288296 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.cpp b/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.cpp
index f0886880802..3cee8b2a184 100644
--- a/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.cpp
+++ b/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.cpp
@@ -80,6 +80,10 @@ void WebAssemblyTargetAsmStreamer::emitIndirectFunctionType(
   OS << '\n';
 }
 
+void WebAssemblyTargetAsmStreamer::emitGlobalImport(StringRef name) {
+  OS << "\t.import_global\t" << name << '\n';
+}
+
 void WebAssemblyTargetAsmStreamer::emitIndIdx(const MCExpr *Value) {
   OS << "\t.indidx  \t" << *Value << '\n';
 }
@@ -111,3 +115,6 @@ void WebAssemblyTargetELFStreamer::emitIndirectFunctionType(
   // Nothing to emit here. TODO: Re-design how linking works and re-evaluate
   // whether it's necessary for .o files to declare indirect function types.
 }
+
+void WebAssemblyTargetELFStreamer::emitGlobalImport(StringRef name) {
+}
\ No newline at end of file
diff --git a/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.h b/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.h
index cf164ca5924..23ac3190243 100644
--- a/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.h
+++ b/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
diff --git a/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp b/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp
index f53cfca9db3..5b4b82eb560 100644
--- a/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp
+++ b/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp
@@ -133,6 +133,11 @@ void WebAssemblyAsmPrinter::EmitEndOfAsmFile(Module &M) {
                                                     Results);
     }
   }
+  for (const auto &G : M.globals()) {
+    if (!G.hasInitializer() && G.hasExternalLinkage()) {
+      getTargetStreamer()->emitGlobalImport(G.getGlobalIdentifier());
+    }
+  }
 }
 
 void WebAssemblyAsmPrinter::EmitConstantPool() {
diff --git a/test/CodeGen/WebAssembly/globl.ll b/test/CodeGen/WebAssembly/globl.ll
index 91d3ade4666..3ebd3d88fb4 100644
--- a/test/CodeGen/WebAssembly/globl.ll
+++ b/test/CodeGen/WebAssembly/globl.ll
@@ -8,3 +8,7 @@ target triple = "wasm32-unknown-unknown"
 define void @foo() {
   ret void
 }
+
+; Check import directives - must be at the end of the file
+; CHECK: .import_global bar{{$}}
+@bar = external global i32