[lld] r320004 - [WebAssembly] Add -u/--undefined argument handling
Sam Clegg via llvm-commits
llvm-commits at lists.llvm.org
Wed Dec 6 19:19:53 PST 2017
Author: sbc
Date: Wed Dec 6 19:19:53 2017
New Revision: 320004
URL: http://llvm.org/viewvc/llvm-project?rev=320004&view=rev
Log:
[WebAssembly] Add -u/--undefined argument handling
Adds a new argument to wasm-lld, `--undefined`, with
similar semantics to the ELF linker. It pulls in symbols
from files contained within a `.a` archive, forcing them
to be included even if the translation unit would not
otherwise be pulled in.
Patch by Nicholas Wilson
Differential Revision: https://reviews.llvm.org/D40724
Added:
lld/trunk/test/wasm/load-undefined.ll
Modified:
lld/trunk/wasm/Driver.cpp
lld/trunk/wasm/Options.td
lld/trunk/wasm/SymbolTable.cpp
lld/trunk/wasm/Symbols.h
Added: lld/trunk/test/wasm/load-undefined.ll
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/wasm/load-undefined.ll?rev=320004&view=auto
==============================================================================
--- lld/trunk/test/wasm/load-undefined.ll (added)
+++ lld/trunk/test/wasm/load-undefined.ll Wed Dec 6 19:19:53 2017
@@ -0,0 +1,38 @@
+; Verify that the -u / --undefined option is able to pull in symbols from
+; an archive, and doesn't error when uses to pull in a symbol already loaded.
+;
+; RUN: llc -filetype=obj -mtriple=wasm32-unknown-unknown-wasm %S/Inputs/ret64.ll -o %t.o
+; RUN: llc -filetype=obj -mtriple=wasm32-unknown-unknown-wasm %S/Inputs/ret32.ll -o %t2.o
+; RUN: llc -filetype=obj -mtriple=wasm32-unknown-unknown-wasm %s -o %t3.o
+; RUN: llvm-ar rcs %t2.a %t2.o
+; RUN: lld -flavor wasm %t3.o %t2.a %t.o -o %t.wasm -u ret32 --undefined ret64
+; RUN: obj2yaml %t.wasm | FileCheck %s
+
+define i32 @_start() local_unnamed_addr {
+entry:
+ ret i32 1
+}
+
+; CHECK: - Type: EXPORT
+; CHECK-NEXT: Exports:
+; CHECK-NEXT: - Name: memory
+; CHECK-NEXT: Kind: MEMORY
+; CHECK-NEXT: Index: 0
+; CHECK-NEXT: - Name: _start
+; CHECK-NEXT: Kind: FUNCTION
+; CHECK-NEXT: Index: 0
+; CHECK-NEXT: - Name: ret32
+; CHECK-NEXT: Kind: FUNCTION
+; CHECK-NEXT: Index: 1
+; CHECK-NEXT: - Name: ret64
+; CHECK-NEXT: Kind: FUNCTION
+; CHECK-NEXT: Index: 2
+; CHECK-NEXT: - Type:
+
+
+; Verify that referencing a symbol that doesn't exist won't work
+; RUN: not lld -flavor wasm %t3.o -o %t.wasm -u symboldoesnotexist 2>&1 | FileCheck -check-prefix=CHECK-UNDEFINED1 %s
+; CHECK-UNDEFINED1: error: undefined symbol: symboldoesnotexist
+
+; RUN: not lld -flavor wasm %t3.o -o %t.wasm --undefined symboldoesnotexist --allow-undefined 2>&1 | FileCheck -check-prefix=CHECK-UNDEFINED2 %s
+; CHECK-UNDEFINED2: function forced with --undefined not found: symboldoesnotexist
Modified: lld/trunk/wasm/Driver.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/wasm/Driver.cpp?rev=320004&r1=320003&r2=320004&view=diff
==============================================================================
--- lld/trunk/wasm/Driver.cpp (original)
+++ lld/trunk/wasm/Driver.cpp Wed Dec 6 19:19:53 2017
@@ -273,6 +273,8 @@ void LinkerDriver::link(ArrayRef<const c
if (Config->Relocatable && !Config->Entry.empty())
error("entry point specified for relocatable output file");
+ if (Config->Relocatable && Args.hasArg(OPT_undefined))
+ error("undefined symbols specified for relocatable output file");
if (!Config->Relocatable) {
if (Config->Entry.empty())
@@ -280,6 +282,10 @@ void LinkerDriver::link(ArrayRef<const c
static WasmSignature Signature = {{}, WASM_TYPE_NORESULT};
addSyntheticUndefinedFunction(Config->Entry, &Signature);
+ // Handle the `--undefined <sym>` options.
+ for (StringRef S : args::getStrings(Args, OPT_undefined))
+ addSyntheticUndefinedFunction(S, nullptr);
+
Config->StackPointerSymbol = addSyntheticGlobal("__stack_pointer", 0);
}
@@ -297,6 +303,18 @@ void LinkerDriver::link(ArrayRef<const c
Symtab->reportRemainingUndefines();
if (errorCount())
return;
+ } else {
+ // When we allow undefined symbols we cannot include those defined in
+ // -u/--undefined since these undefined symbols have only names and no
+ // function signature, which means they cannot be written to the final
+ // output.
+ for (StringRef S : args::getStrings(Args, OPT_undefined)) {
+ Symbol *Sym = Symtab->find(S);
+ if (!Sym->isDefined())
+ error("function forced with --undefined not found: " + Sym->getName());
+ }
+ if (errorCount())
+ return;
}
if (!Config->Entry.empty()) {
Modified: lld/trunk/wasm/Options.td
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/wasm/Options.td?rev=320004&r1=320003&r2=320004&view=diff
==============================================================================
--- lld/trunk/wasm/Options.td (original)
+++ lld/trunk/wasm/Options.td Wed Dec 6 19:19:53 2017
@@ -6,6 +6,11 @@ class F<string name>: Flag<["--", "-"],
class J<string name>: Joined<["--", "-"], name>;
class S<string name>: Separate<["--", "-"], name>;
+multiclass Eq<string name> {
+ def "": Separate<["--", "-"], name>;
+ def _eq: Joined<["--", "-"], name # "=">, Alias<!cast<Separate>(NAME)>;
+}
+
def L: JoinedOrSeparate<["-"], "L">, MetaVarName<"<dir>">,
HelpText<"Add a directory to the library search path">;
@@ -52,6 +57,9 @@ def strip_all: F<"strip-all">, HelpText<
def strip_debug: F<"strip-debug">, HelpText<"Strip debugging information">;
+defm undefined: Eq<"undefined">,
+ HelpText<"Force undefined symbol during linking">;
+
def z: JoinedOrSeparate<["-"], "z">, MetaVarName<"<option>">,
HelpText<"Linker option extensions">;
@@ -89,3 +97,4 @@ def alias_max_memory_m: Flag<["-"], "m">
def alias_relocatable_r: Flag<["-"], "r">, Alias<relocatable>;
def alias_entry_e: JoinedOrSeparate<["-"], "e">, Alias<entry>;
def alias_entry_entry: J<"entry=">, Alias<entry>;
+def alias_undefined_u: JoinedOrSeparate<["-"], "u">, Alias<undefined>;
Modified: lld/trunk/wasm/SymbolTable.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/wasm/SymbolTable.cpp?rev=320004&r1=320003&r2=320004&view=diff
==============================================================================
--- lld/trunk/wasm/SymbolTable.cpp (original)
+++ lld/trunk/wasm/SymbolTable.cpp Wed Dec 6 19:19:53 2017
@@ -118,6 +118,10 @@ static void checkSymbolTypes(const Symbo
// For function symbols, optionally check the function signature matches too.
if (!NewIsFunction || !Config->CheckSignatures)
return;
+ // Skip the signature check if the existing function has no signature (e.g.
+ // if it is an undefined symbol generated by --undefined command line flag).
+ if (!Existing.hasFunctionType())
+ return;
DEBUG(dbgs() << "checkSymbolTypes: " << New.Name << "\n");
assert(NewSig);
Modified: lld/trunk/wasm/Symbols.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/wasm/Symbols.h?rev=320004&r1=320003&r2=320004&view=diff
==============================================================================
--- lld/trunk/wasm/Symbols.h (original)
+++ lld/trunk/wasm/Symbols.h Wed Dec 6 19:19:53 2017
@@ -69,6 +69,7 @@ public:
uint32_t getGlobalIndex() const;
uint32_t getFunctionIndex() const;
+ bool hasFunctionType() const { return FunctionType != nullptr; }
const WasmSignature &getFunctionType() const;
uint32_t getOutputIndex() const;
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