[WebAssembly] Refactor WasmSignature and use it for MCSymbolWasm

MCContext does not destroy MCSymbols on shutdown. So, rather than putting
SmallVectors (which may heap-allocate) inside MCSymbolWasm, use unowned pointer
to a WasmSignature instead. The signatures are now owned by the AsmPrinter.
Also uses WasmSignature instead of param and result vectors in TargetStreamer,
and leaves some TODOs for further simplification.

 Differential Revision: https://reviews.llvm.org/D52580

llvm-svn: 343733

1 files changed, 5 insertions, 2 deletions

diff --git a/llvm/lib/MC/WasmObjectWriter.cpp b/llvm/lib/MC/WasmObjectWriter.cpp
index 2c28f01958f..cbbe161ae82 100644
--- a/llvm/lib/MC/WasmObjectWriter.cpp
+++ b/llvm/lib/MC/WasmObjectWriter.cpp
@@ -58,6 +58,7 @@ struct SectionBookkeeping {
 
 // The signature of a wasm function, in a struct capable of being used as a
 // DenseMap key.
+// TODO: Consider using WasmSignature directly instead.
 struct WasmFunctionType {
   // Support empty and tombstone instances, needed by DenseMap.
   enum { Plain, Empty, Tombstone } State;
@@ -1049,8 +1050,10 @@ uint32_t WasmObjectWriter::registerFunctionType(const MCSymbolWasm &Symbol) {
 
   WasmFunctionType F;
   const MCSymbolWasm *ResolvedSym = ResolveSymbol(Symbol);
-  F.Returns = ResolvedSym->getReturns();
-  F.Params = ResolvedSym->getParams();
+  if (auto *Sig = ResolvedSym->getSignature()) {
+    F.Returns = Sig->Returns;
+    F.Params = Sig->Params;
+  }
 
   auto Pair =
       FunctionTypeIndices.insert(std::make_pair(F, FunctionTypes.size()));