[WebAssembly] Support CFI for WebAssembly target

Summary: This patch implements CFI for WebAssembly. It modifies the
LowerTypeTest pass to pre-assign table indexes to functions that are
called indirectly, and lowers type checks to test against the
appropriate table indexes. It also modifies the WebAssembly backend to
support a special ".indidx" assembly directive that propagates the table
index assignments out to the linker.

Patch by Dominic Chen

Differential Revision: https://reviews.llvm.org/D21768

llvm-svn: 277398

1 files changed, 11 insertions, 1 deletions

diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.cpp b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.cpp
index 3d61c15..6ca95aa 100644
--- a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.cpp
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.cpp
@@ -67,13 +67,18 @@ void WebAssemblyTargetAsmStreamer::emitEndFunc() { OS << "\t.endfunc\n"; }
 void WebAssemblyTargetAsmStreamer::emitIndirectFunctionType(
     StringRef name, SmallVectorImpl<MVT> &SignatureVTs, size_t NumResults) {
   OS << "\t.functype\t" << name;
-  if (NumResults == 0) OS << ", void";
+  if (NumResults == 0)
+    OS << ", void";
   for (auto Ty : SignatureVTs) {
     OS << ", " << WebAssembly::TypeToString(Ty);
   }
   OS << "\n";
 }
 
+void WebAssemblyTargetAsmStreamer::emitIndIdx(const MCExpr *Value) {
+  OS << "\t.indidx  \t" << *Value << '\n';
+}
+
 // FIXME: What follows is not the real binary encoding.
 
 static void EncodeTypes(MCStreamer &Streamer, ArrayRef<MVT> Types) {
@@ -100,3 +105,8 @@ void WebAssemblyTargetELFStreamer::emitLocal(ArrayRef<MVT> Types) {
 void WebAssemblyTargetELFStreamer::emitEndFunc() {
   Streamer.EmitIntValue(WebAssembly::DotEndFunc, sizeof(uint64_t));
 }
+
+void WebAssemblyTargetELFStreamer::emitIndIdx(const MCExpr *Value) {
+  Streamer.EmitIntValue(WebAssembly::DotIndIdx, sizeof(uint64_t));
+  Streamer.EmitValue(Value, sizeof(uint64_t));
+}