[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

4 files changed, 28 insertions, 3 deletions

diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h
index 001bd7f1fc4..7a32ddd5793 100644
--- a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h
@@ -59,6 +59,7 @@ enum Directive {
   DotResult = UINT64_MAX - 1,  ///< .result
   DotLocal = UINT64_MAX - 2,   ///< .local
   DotEndFunc = UINT64_MAX - 3, ///< .endfunc
+  DotIndIdx = UINT64_MAX - 4,  /// < .indidx
 };
 
 } // end namespace WebAssembly
@@ -123,7 +124,8 @@ inline unsigned GetDefaultP2Align(unsigned Opcode) {
   case WebAssembly::STORE_I64:
   case WebAssembly::STORE_F64:
     return 3;
-  default: llvm_unreachable("Only loads and stores have p2align values");
+  default:
+    llvm_unreachable("Only loads and stores have p2align values");
   }
 }
 
diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.cpp b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.cpp
index 3d61c15717b..6ca95aaa03b 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));
+}
diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.h b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.h
index 51354ef22d7..2e3e9bccdb1 100644
--- a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.h
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyTargetStreamer.h
@@ -43,6 +43,8 @@ public:
                                         size_t NumResults) {
     llvm_unreachable("emitIndirectFunctionType not implemented");
   }
+  /// .indidx
+  virtual void emitIndIdx(const MCExpr *Value) = 0;
 };
 
 /// This part is for ascii assembly output
@@ -59,6 +61,7 @@ public:
   void emitIndirectFunctionType(StringRef name,
                                 SmallVectorImpl<MVT> &SignatureVTs,
                                 size_t NumResults) override;
+  void emitIndIdx(const MCExpr *Value) override;
 };
 
 /// This part is for ELF object output
@@ -70,6 +73,7 @@ public:
   void emitResult(ArrayRef<MVT> Types) override;
   void emitLocal(ArrayRef<MVT> Types) override;
   void emitEndFunc() override;
+  void emitIndIdx(const MCExpr *Value) override;
 };
 
 } // end namespace llvm
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp
index 54e9f7f5290..b95d77b770a 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp
@@ -14,10 +14,10 @@
 ///
 //===----------------------------------------------------------------------===//
 
-#include "WebAssembly.h"
 #include "InstPrinter/WebAssemblyInstPrinter.h"
 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
 #include "MCTargetDesc/WebAssemblyTargetStreamer.h"
+#include "WebAssembly.h"
 #include "WebAssemblyMCInstLower.h"
 #include "WebAssemblyMachineFunctionInfo.h"
 #include "WebAssemblyRegisterInfo.h"
@@ -183,6 +183,15 @@ void WebAssemblyAsmPrinter::EmitFunctionBodyStart() {
 
   SmallVector<MVT, 4> ResultVTs;
   const Function &F(*MF->getFunction());
+
+  // Emit the function index.
+  if (MDNode *Idx = F.getMetadata("wasm.index")) {
+    assert(Idx->getNumOperands() == 1);
+
+    getTargetStreamer()->emitIndIdx(AsmPrinter::lowerConstant(
+        cast<ConstantAsMetadata>(Idx->getOperand(0))->getValue()));
+  }
+
   ComputeLegalValueVTs(F, TM, F.getReturnType(), ResultVTs);
 
   // If the return type needs to be legalized it will get converted into