[PATCH] D41922: [WebAssembly] When loading libraries look for companion `.imports` file

[Sam Clegg via Phabricator via llvm-commits]

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

This allows libraries to supply a list of symbols which are
allowed to be undefined at link time (i.e. result in imports)
without forcing the user/driver to supply -allow-undefined-file.

See https://github.com/WebAssembly/tool-conventions/issues/35


Repository:
  rLLD LLVM Linker

https://reviews.llvm.org/D41922

Files:
  test/wasm/archive.ll
  wasm/Driver.cpp


Index: wasm/Driver.cpp
===================================================================
--- wasm/Driver.cpp
+++ wasm/Driver.cpp
@@ -173,11 +173,21 @@
     Files.push_back(make<ObjFile>(MBRef));
 }
 
+static void processImportFile(StringRef Filename) {
+  if (Optional<MemoryBufferRef> Buf = readFile(Filename))
+    for (StringRef Sym : args::getLines(*Buf))
+      Config->AllowUndefinedSymbols.insert(Sym);
+}
+
 // Add a given library by searching it from input search paths.
 void LinkerDriver::addLibrary(StringRef Name) {
   for (StringRef Dir : Config->SearchPaths) {
     if (Optional<std::string> S = findFile(Dir, "lib" + Name + ".a")) {
       addFile(*S);
+      SmallString<128> ImportFile = Dir;
+      path::append(ImportFile, "lib" + Name + ".imports");
+      if (fs::exists(ImportFile))
+        processImportFile(ImportFile.str());
       return;
     }
   }
@@ -257,9 +267,7 @@
       args::getZOptionValue(Args, OPT_z, "stack-size", WasmPageSize);
 
   if (auto *Arg = Args.getLastArg(OPT_allow_undefined_file))
-    if (Optional<MemoryBufferRef> Buf = readFile(Arg->getValue()))
-      for (StringRef Sym : args::getLines(*Buf))
-        Config->AllowUndefinedSymbols.insert(Sym);
+    processImportFile(Arg->getValue());
 
   if (Config->OutputFile.empty())
     error("no output file specified");
Index: test/wasm/archive.ll
===================================================================
--- test/wasm/archive.ll
+++ test/wasm/archive.ll
@@ -2,30 +2,41 @@
 ; RUN: llc -filetype=obj -mtriple=wasm32-unknown-unknown-wasm %S/Inputs/archive1.ll -o %t.a1.o
 ; RUN: llc -filetype=obj -mtriple=wasm32-unknown-unknown-wasm %S/Inputs/archive2.ll -o %t.a2.o
 ; RUN: llc -filetype=obj -mtriple=wasm32-unknown-unknown-wasm %S/Inputs/hello.ll -o %t.a3.o
-; RUN: llvm-ar rcs %t.a %t.a1.o %t.a2.o %t.a3.o
-; RUN: lld -flavor wasm %t.a %t.o -o %t.wasm
+; RUN: mkdir -p %t.dir
+; RUN: rm %t.dir/libtest.imports
+; RUN: llvm-ar rcs %t.dir/libtest.a %t.a1.o %t.a2.o %t.a3.o
+; RUN: not lld -flavor wasm %t.dir/libtest.a %t.o -o %t.wasm 2>&1 | FileCheck -check-prefix=CHECK-UNDEFINED %s
+; RUN: not lld -flavor wasm -L%t.dir -ltest %t.o -o %t.wasm 2>&1 | FileCheck -check-prefix=CHECK-UNDEFINED %s
+
+; CHECK-UNDEFINED: undefined symbol: missing_func
+
+; RUN: echo 'missing_func' > %t.dir/libtest.imports
+; RUN: lld -flavor wasm -L%t.dir -ltest %t.o -o %t.wasm
+
 ; RUN: llvm-nm -a %t.wasm | FileCheck %s
 
 declare i32 @foo() local_unnamed_addr #1
+declare i32 @missing_func() local_unnamed_addr #1
 
 define i32 @_start() local_unnamed_addr #0 {
 entry:
-  %call = tail call i32 @foo() #2
-  ret i32 %call
+  %call1 = call i32 @foo() #2
+  %call2 = call i32 @missing_func() #2
+  ret i32 %call2
 }
 
 ; Verify that multually dependant object files in an archive is handled
 ; correctly.
 
-; CHECK:      00000002 T _start
-; CHECK-NEXT: 00000002 T _start
-; CHECK-NEXT: 00000000 T bar
-; CHECK-NEXT: 00000000 T bar
-; CHECK-NEXT: 00000001 T foo
-; CHECK-NEXT: 00000001 T foo
+; CHECK:      00000003 T _start
+; CHECK-NEXT: 00000003 T _start
+; CHECK-NEXT: 00000001 T bar
+; CHECK-NEXT: 00000001 T bar
+; CHECK-NEXT: 00000002 T foo
+; CHECK-NEXT: 00000002 T foo
 
 ; Verify that symbols from unused objects don't appear in the symbol table
 ; CHECK-NOT: hello
 
 ; Specifying the same archive twice is allowed.
-; RUN: lld -flavor wasm %t.a %t.a %t.o -o %t.wasm
+; RUN: lld -flavor wasm -L%t.dir -ltest -ltest %t.o -o %t.wasm


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