[WebAssembly] Initial WebAssembly support in clang

This implements basic support for compiling (though not yet assembling
or linking) for a WebAssembly target. Note that ABI details are not yet
finalized, and may change.

Differential Revision: http://reviews.llvm.org/D12002

llvm-svn: 246814

1 files changed, 55 insertions, 2 deletions

diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index eb245b38e09..fdb1b1815c4 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -484,6 +484,8 @@ static bool isNoCommonDefault(const llvm::Triple &Triple) {
     return false;
 
   case llvm::Triple::xcore:
+  case llvm::Triple::wasm32:
+  case llvm::Triple::wasm64:
     return true;
   }
 }
@@ -1553,6 +1555,25 @@ static const char *getX86TargetCPU(const ArgList &Args,
   }
 }
 
+/// Get the (LLVM) name of the WebAssembly cpu we are targeting.
+static StringRef getWebAssemblyTargetCPU(const ArgList &Args) {
+  // If we have -mcpu=, use that.
+  if (Arg *A = Args.getLastArg(options::OPT_mcpu_EQ)) {
+    StringRef CPU = A->getValue();
+
+#ifdef __wasm__
+    // Handle "native" by examining the host. "native" isn't meaningful when
+    // cross compiling, so only support this when the host is also WebAssembly.
+    if (CPU == "native")
+      return llvm::sys::getHostCPUName();
+#endif
+
+    return CPU;
+  }
+
+  return "generic";
+}
+
 static std::string getCPUName(const ArgList &Args, const llvm::Triple &T,
                               bool FromAs = false) {
   switch (T.getArch()) {
@@ -1625,6 +1646,10 @@ static std::string getCPUName(const ArgList &Args, const llvm::Triple &T,
   case llvm::Triple::r600:
   case llvm::Triple::amdgcn:
     return getR600TargetGPU(Args);
+
+  case llvm::Triple::wasm32:
+  case llvm::Triple::wasm64:
+    return getWebAssemblyTargetCPU(Args);
   }
 }
 
@@ -2074,6 +2099,24 @@ static void getAArch64TargetFeatures(const Driver &D,
     Features.push_back("+reserve-x18");
 }
 
+static void getWebAssemblyTargetFeatures(const ArgList &Args,
+                                         std::vector<const char *> &Features) {
+  for (const Arg *A : Args.filtered(options::OPT_m_wasm_Features_Group)) {
+    StringRef Name = A->getOption().getName();
+    A->claim();
+
+    // Skip over "-m".
+    assert(Name.startswith("m") && "Invalid feature name.");
+    Name = Name.substr(1);
+
+    bool IsNegative = Name.startswith("no-");
+    if (IsNegative)
+      Name = Name.substr(3);
+
+    Features.push_back(Args.MakeArgString((IsNegative ? "-" : "+") + Name));
+  }
+}
+
 static void getTargetFeatures(const Driver &D, const llvm::Triple &Triple,
                               const ArgList &Args, ArgStringList &CmdArgs,
                               bool ForAS) {
@@ -2111,6 +2154,10 @@ static void getTargetFeatures(const Driver &D, const llvm::Triple &Triple,
   case llvm::Triple::x86_64:
     getX86TargetFeatures(D, Triple, Args, Features);
     break;
+  case llvm::Triple::wasm32:
+  case llvm::Triple::wasm64:
+    getWebAssemblyTargetFeatures(Args, Features);
+    break;
   }
 
   // Find the last of each feature.
@@ -2590,9 +2637,15 @@ static bool areOptimizationsEnabled(const ArgList &Args) {
 
 static bool shouldUseFramePointerForTarget(const ArgList &Args,
                                            const llvm::Triple &Triple) {
-  // XCore never wants frame pointers, regardless of OS.
-  if (Triple.getArch() == llvm::Triple::xcore) {
+  switch (Triple.getArch()) {
+  case llvm::Triple::xcore:
+  case llvm::Triple::wasm32:
+  case llvm::Triple::wasm64:
+    // XCore never wants frame pointers, regardless of OS.
+    // WebAssembly never wants frame pointers.
     return false;
+  default:
+    break;
   }
 
   if (Triple.isOSLinux()) {