[WebAssembly] Add default -allow-undefined-file to linker args

[sbc100]

Summary

This directs lld to ignore undefined symbols listed in that
file and is part of my ongoing lld work.

Also, don't use the outdated lib32/lib64 naming of files
within the sysroot. The more modern/flexible approach
IIUC is to use seperate sysroots or /lib/<target-tripple>
and /include/<target-tripple>.

[sbc100]

rebase

[sbc100]

don't add syms file with -nostdlib

[sbc100]

rebase

[sbc100]

ptal

lib/Driver/ToolChains/WebAssembly.cpp

void wasm::Linker::ConstructJob(Compilation &C, const JobAction &JA,
 
   if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nodefaultlibs)) {
     if (D.CCCIsCXX())
       ToolChain.AddCXXStdlibLibArgs(Args, CmdArgs);
 
     if (Args.hasArg(options::OPT_pthread))
       CmdArgs.push_back("-lpthread");
 
+    CmdArgs.push_back("-allow-undefined-file");
+    CmdArgs.push_back(Args.MakeArgString(ToolChain.GetFilePath("wasm.syms")));
     CmdArgs.push_back("-lc");
     CmdArgs.push_back("-lcompiler_rt");
   }
 
   if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nostartfiles))
     CmdArgs.push_back(Args.MakeArgString(ToolChain.GetFilePath("crtn.o")));
 
   CmdArgs.push_back("-o");
   CmdArgs.push_back(Output.getFilename());
 
   C.addCommand(llvm::make_unique<Command>(JA, *this, Linker, CmdArgs, Inputs));
 }
 
 WebAssembly::WebAssembly(const Driver &D, const llvm::Triple &Triple,
                          const llvm::opt::ArgList &Args)
   : ToolChain(D, Triple, Args) {
 
   assert(Triple.isArch32Bit() != Triple.isArch64Bit());
 
   getProgramPaths().push_back(getDriver().getInstalledDir());
 
-  getFilePaths().push_back(
-      getDriver().SysRoot + "/lib" + (Triple.isArch32Bit() ? "32" : "64"));
+  getFilePaths().push_back(getDriver().SysRoot + "/lib");
 }
 
 bool WebAssembly::IsMathErrnoDefault() const { return false; }
 
 bool WebAssembly::IsObjCNonFragileABIDefault() const { return true; }
 
 bool WebAssembly::UseObjCMixedDispatch() const { return true; }
 

test/Driver/wasm-toolchain.c

 
 // RUN: %clang %s -### -target wasm32-unknown-unknown -fvisibility=default 2>&1 | FileCheck -check-prefix=FVISIBILITY_DEFAULT %s
 // FVISIBILITY_DEFAULT-NOT: hidden
 
 // A basic C link command-line.
 
 // RUN: %clang -### -no-canonical-prefixes -target wasm32-unknown-unknown --sysroot=/foo %s 2>&1 | FileCheck -check-prefix=LINK %s
 // LINK: clang{{.*}}" "-cc1" {{.*}} "-o" "[[temp:[^"]*]]"
-// LINK: lld{{.*}}" "-flavor" "wasm" "-L/foo/lib32" "crt1.o" "crti.o" "[[temp]]" "-lc" "-lcompiler_rt" "crtn.o" "-o" "a.out"
+// LINK: lld{{.*}}" "-flavor" "wasm" "-L/foo/lib" "crt1.o" "crti.o" "[[temp]]" "-lc" "-lcompiler_rt" "crtn.o" "-o" "a.out"
 
 // A basic C link command-line with optimization. WebAssembly is somewhat
 // special in enabling --gc-sections by default.
 
 // RUN: %clang -### -O2 -no-canonical-prefixes -target wasm32-unknown-unknown --sysroot=/foo %s 2>&1 | FileCheck -check-prefix=LINK_OPT %s
 // LINK_OPT: clang{{.*}}" "-cc1" {{.*}} "-o" "[[temp:[^"]*]]"
-// LINK_OPT: lld{{.*}}" "-flavor" "wasm" "--gc-sections" "-L/foo/lib32" "crt1.o" "crti.o" "[[temp]]" "-lc" "-lcompiler_rt" "crtn.o" "-o" "a.out"
+// LINK_OPT: lld{{.*}}" "-flavor" "wasm" "--gc-sections" "-L/foo/lib" "crt1.o" "crti.o" "[[temp]]" "-lc" "-lcompiler_rt" "crtn.o" "-o" "a.out"
 
 // Ditto, but ensure that a user --no-gc-sections comes after the
 // default --gc-sections.
 
 // RUN: %clang -### -O2 -no-canonical-prefixes -target wasm32-unknown-unknown --sysroot=/foo -Wl,--no-gc-sections %s 2>&1 | FileCheck -check-prefix=NO_GC_SECTIONS %s
 // NO_GC_SECTIONS: clang{{.*}}" "-cc1" {{.*}} "-o" "[[temp:[^"]*]]"
-// NO_GC_SECTIONS: lld{{.*}}" "-flavor" "wasm" "--gc-sections" "-L/foo/lib32" "crt1.o" "crti.o" "--no-gc-sections" "[[temp]]" "-lc" "-lcompiler_rt" "crtn.o" "-o" "a.out"
+// NO_GC_SECTIONS: lld{{.*}}" "-flavor" "wasm" "--gc-sections" "-L/foo/lib" "crt1.o" "crti.o" "--no-gc-sections" "[[temp]]" "-lc" "-lcompiler_rt" "crtn.o" "-o" "a.out"