[WebAssembly] Remove uses of ThreadModel

Summary:
In the clang UI, replaces -mthread-model posix with -matomics as the
source of truth on threading. In the backend, replaces
-thread-model=posix with the atomics target feature, which is now
collected on the WebAssemblyTargetMachine along with all other used
features. These collected features will also be used to emit the
target features section in the future.

The default configuration for the backend is thread-model=posix and no
atomics, which was previously an invalid configuration. This change
makes the default valid because the thread model is ignored.

A side effect of this change is that objects are never emitted with
passive segments. It will instead be up to the linker to decide
whether sections should be active or passive based on whether atomics
are used in the final link.

Reviewers: aheejin, sbc100, dschuff

Subscribers: mehdi_amini, jgravelle-google, hiraditya, sunfish, steven_wu, dexonsmith, rupprecht, jfb, jdoerfert, cfe-commits, llvm-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D58742

llvm-svn: 355112

1 files changed, 28 insertions, 39 deletions

diff --git a/clang/lib/Driver/ToolChains/WebAssembly.cpp b/clang/lib/Driver/ToolChains/WebAssembly.cpp
index f076b528ce4..ce28d447ff2 100644
--- a/clang/lib/Driver/ToolChains/WebAssembly.cpp
+++ b/clang/lib/Driver/ToolChains/WebAssembly.cpp
@@ -20,27 +20,6 @@ using namespace clang::driver::toolchains;
 using namespace clang;
 using namespace llvm::opt;
 
-void parseThreadArgs(const Driver &Driver, const ArgList &DriverArgs,
-                     bool &Pthread, StringRef &ThreadModel,
-                     bool CheckForErrors = true) {
-  // Default value for -pthread / -mthread-model options, each being false /
-  // "single".
-  Pthread =
-      DriverArgs.hasFlag(options::OPT_pthread, options::OPT_no_pthread, false);
-  ThreadModel =
-      DriverArgs.getLastArgValue(options::OPT_mthread_model, "single");
-  if (!CheckForErrors)
-    return;
-
-  // Did user explicitly specify -mthread-model / -pthread?
-  bool HasThreadModel = DriverArgs.hasArg(options::OPT_mthread_model);
-  bool HasPthread = Pthread && DriverArgs.hasArg(options::OPT_pthread);
-  // '-pthread' cannot be used with '-mthread-model single'
-  if (HasPthread && HasThreadModel && ThreadModel == "single")
-    Driver.Diag(diag::err_drv_argument_not_allowed_with)
-        << "-pthread" << "-mthread-model single";
-}
-
 wasm::Linker::Linker(const ToolChain &TC)
     : GnuTool("wasm::Linker", "lld", TC) {}
 
@@ -145,15 +124,36 @@ void WebAssembly::addClangTargetOptions(const ArgList &DriverArgs,
                          options::OPT_fno_use_init_array, true))
     CC1Args.push_back("-fuse-init-array");
 
-  // Either '-mthread-model posix' or '-pthread' sets '-target-feature
-  // +atomics'. We intentionally didn't create '-matomics' and set the atomics
-  // target feature here depending on the other two options.
-  bool Pthread = false;
-  StringRef ThreadModel = "";
-  parseThreadArgs(getDriver(), DriverArgs, Pthread, ThreadModel);
-  if (Pthread || ThreadModel != "single") {
+  // '-pthread' implies '-target-feature +atomics' and
+  // '-target-feature +bulk-memory'
+  if (DriverArgs.hasFlag(options::OPT_pthread, options::OPT_no_pthread,
+                         false)) {
+    if (DriverArgs.hasFlag(options::OPT_mno_atomics, options::OPT_matomics,
+                           false))
+      getDriver().Diag(diag::err_drv_argument_not_allowed_with)
+          << "-pthread"
+          << "-mno-atomics";
+    if (DriverArgs.hasFlag(options::OPT_mno_bulk_memory,
+                           options::OPT_mbulk_memory, false))
+      getDriver().Diag(diag::err_drv_argument_not_allowed_with)
+          << "-pthread"
+          << "-mno-bulk-memory";
     CC1Args.push_back("-target-feature");
     CC1Args.push_back("+atomics");
+    CC1Args.push_back("-target-feature");
+    CC1Args.push_back("+bulk-memory");
+  }
+
+  // '-matomics' implies '-mbulk-memory'
+  if (DriverArgs.hasFlag(options::OPT_matomics, options::OPT_mno_atomics,
+                         false)) {
+    if (DriverArgs.hasFlag(options::OPT_mno_bulk_memory,
+                           options::OPT_mbulk_memory, false))
+      getDriver().Diag(diag::err_drv_argument_not_allowed_with)
+          << "-matomics"
+          << "-mno-bulk-memory";
+    CC1Args.push_back("-target-feature");
+    CC1Args.push_back("+bulk-memory");
   }
 }
 
@@ -212,17 +212,6 @@ void WebAssembly::AddCXXStdlibLibArgs(const llvm::opt::ArgList &Args,
   }
 }
 
-std::string WebAssembly::getThreadModel(const ArgList &DriverArgs) const {
-  // The WebAssembly MVP does not yet support threads. We set this to "posix"
-  // when '-pthread' is set.
-  bool Pthread = false;
-  StringRef ThreadModel = "";
-  parseThreadArgs(getDriver(), DriverArgs, Pthread, ThreadModel, false);
-  if (Pthread)
-    return "posix";
-  return ThreadModel;
-}
-
 Tool *WebAssembly::buildLinker() const {
   return new tools::wasm::Linker(*this);
 }