From af3b9d0570bb2e5d67554a705ffe383377305660 Mon Sep 17 00:00:00 2001
From: Sam Clegg <sbc@chromium.org>
Date: Thu, 7 Feb 2019 01:53:50 +0000
Subject: [PATCH] [WebAssembly] Honor WASM_SYMBOL_EXPORT symbol flag

This flag means that symbol should be exported in the final binary.

The reason for this change is to allow source level annotations to
trigger a given symbol to be exported:
https://github.com/emscripten-core/emscripten/issues/7702

Differential Revision: https://reviews.llvm.org/D57869

llvm-svn: 353364
---
 lld/test/wasm/export.ll | 23 ++++++++++++++++++++++-
 lld/wasm/Symbols.cpp    |  2 +-
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/lld/test/wasm/export.ll b/lld/test/wasm/export.ll
index 519aafebbe23..48b66ee10f7b 100644
--- a/lld/test/wasm/export.ll
+++ b/lld/test/wasm/export.ll
@@ -3,13 +3,29 @@
 ; RUN: wasm-ld --export=hidden_function -o %t.wasm %t.o
 ; RUN: obj2yaml %t.wasm | FileCheck %s
 
+@llvm.used = appending global [1 x i8*] [i8* bitcast (i32 ()* @used_function to i8*)], section "llvm.metadata"
+
 target triple = "wasm32-unknown-unknown"
 
+; Not exported by default, but forced via commandline
 define hidden i32 @hidden_function() local_unnamed_addr {
 entry:
   ret i32 0
 }
 
+; Not exported by default
+define i32 @default_function() local_unnamed_addr {
+entry:
+  ret i32 0
+}
+
+; Exported because its part of llvm.used
+define i32 @used_function() local_unnamed_addr {
+entry:
+  ret i32 0
+}
+
+; Exported by default
 define void @_start() local_unnamed_addr {
 entry:
   ret void
@@ -17,6 +33,8 @@ entry:
 
 ; CHECK-ERROR: error: symbol exported via --export not found: missing
 
+; CHECK-NOT: - Name: default_function
+
 ; CHECK:        - Type:            EXPORT
 ; CHECK-NEXT:     Exports:
 ; CHECK-NEXT:       - Name:            memory
@@ -31,7 +49,10 @@ entry:
 ; CHECK-NEXT:       - Name:            hidden_function
 ; CHECK-NEXT:         Kind:            FUNCTION
 ; CHECK-NEXT:         Index:           1
-; CHECK-NEXT:       - Name:            _start
+; CHECK-NEXT:       - Name:            used_function
 ; CHECK-NEXT:         Kind:            FUNCTION
 ; CHECK-NEXT:         Index:           2
+; CHECK-NEXT:       - Name:            _start
+; CHECK-NEXT:         Kind:            FUNCTION
+; CHECK-NEXT:         Index:           3
 ; CHECK-NEXT:   - Type:            CODE
diff --git a/lld/wasm/Symbols.cpp b/lld/wasm/Symbols.cpp
index 4721e35f9f86..60030bef3fa6 100644
--- a/lld/wasm/Symbols.cpp
+++ b/lld/wasm/Symbols.cpp
@@ -116,7 +116,7 @@ bool Symbol::isExported() const {
   if (Config->ExportDynamic && !isHidden())
     return true;
 
-  return false;
+  return Flags & WASM_SYMBOL_EXPORTED;
 }
 
 uint32_t FunctionSymbol::getFunctionIndex() const {