[WebAssembly] Allow multivalue types in block signature operands

Summary:
Renames `ExprType` to the more apt `BlockType` and adds a variant for
multivalue blocks. Currently non-void blocks are only generated at the
end of functions where the block return type needs to agree with the
function return type, and that remains true for multivalue
blocks. That invariant means that the actual signature does not need
to be stored in the block signature `MachineOperand` because it can be
inferred by `WebAssemblyMCInstLower` from the return type of the
parent function. `WebAssemblyMCInstLower` continues to lower block
signature operands to immediates when possible but lowers multivalue
signatures to function type symbols. The AsmParser and Disassembler
are updated to handle multivalue block types as well.

Reviewers: aheejin, dschuff, aardappel

Subscribers: sbc100, jgravelle-google, hiraditya, sunfish, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D68889

llvm-svn: 374933

15 files changed, 181 insertions, 117 deletions

diff --git a/llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp b/llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp
index bfa16a71e11..53a96fd6a97 100644
--- a/llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp
+++ b/llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp
@@ -313,16 +313,17 @@ public:
     return Optional<wasm::ValType>();
   }
 
-  WebAssembly::ExprType parseBlockType(StringRef ID) {
-    return StringSwitch<WebAssembly::ExprType>(ID)
-        .Case("i32", WebAssembly::ExprType::I32)
-        .Case("i64", WebAssembly::ExprType::I64)
-        .Case("f32", WebAssembly::ExprType::F32)
-        .Case("f64", WebAssembly::ExprType::F64)
-        .Case("v128", WebAssembly::ExprType::V128)
-        .Case("exnref", WebAssembly::ExprType::Exnref)
-        .Case("void", WebAssembly::ExprType::Void)
-        .Default(WebAssembly::ExprType::Invalid);
+  WebAssembly::BlockType parseBlockType(StringRef ID) {
+    // Multivalue block types are handled separately in parseSignature
+    return StringSwitch<WebAssembly::BlockType>(ID)
+        .Case("i32", WebAssembly::BlockType::I32)
+        .Case("i64", WebAssembly::BlockType::I64)
+        .Case("f32", WebAssembly::BlockType::F32)
+        .Case("f64", WebAssembly::BlockType::F64)
+        .Case("v128", WebAssembly::BlockType::V128)
+        .Case("exnref", WebAssembly::BlockType::Exnref)
+        .Case("void", WebAssembly::BlockType::Void)
+        .Default(WebAssembly::BlockType::Invalid);
   }
 
   bool parseRegTypeList(SmallVectorImpl<wasm::ValType> &Types) {
@@ -416,7 +417,7 @@ public:
   }
 
   void addBlockTypeOperand(OperandVector &Operands, SMLoc NameLoc,
-                           WebAssembly::ExprType BT) {
+                           WebAssembly::BlockType BT) {
     Operands.push_back(std::make_unique<WebAssemblyOperand>(
         WebAssemblyOperand::Integer, NameLoc, NameLoc,
         WebAssemblyOperand::IntOp{static_cast<int64_t>(BT)}));
@@ -456,6 +457,7 @@ public:
     // If this instruction is part of a control flow structure, ensure
     // proper nesting.
     bool ExpectBlockType = false;
+    bool ExpectFuncType = false;
     if (Name == "block") {
       push(Block);
       ExpectBlockType = true;
@@ -494,6 +496,10 @@ public:
       if (pop(Name, Function) || ensureEmptyNestingStack())
         return true;
     } else if (Name == "call_indirect" || Name == "return_call_indirect") {
+      ExpectFuncType = true;
+    }
+
+    if (ExpectFuncType || (ExpectBlockType && Lexer.is(AsmToken::LParen))) {
       // This has a special TYPEINDEX operand which in text we
       // represent as a signature, such that we can re-build this signature,
       // attach it to an anonymous symbol, which is what WasmObjectWriter
@@ -502,6 +508,8 @@ public:
       auto Signature = std::make_unique<wasm::WasmSignature>();
       if (parseSignature(Signature.get()))
         return true;
+      // Got signature as block type, don't need more
+      ExpectBlockType = false;
       auto &Ctx = getStreamer().getContext();
       // The "true" here will cause this to be a nameless symbol.
       MCSymbol *Sym = Ctx.createTempSymbol("typeindex", true);
@@ -526,7 +534,7 @@ public:
         if (ExpectBlockType) {
           // Assume this identifier is a block_type.
           auto BT = parseBlockType(Id.getString());
-          if (BT == WebAssembly::ExprType::Invalid)
+          if (BT == WebAssembly::BlockType::Invalid)
             return error("Unknown block type: ", Id);
           addBlockTypeOperand(Operands, NameLoc, BT);
           Parser.Lex();
@@ -594,7 +602,7 @@ public:
     }
     if (ExpectBlockType && Operands.size() == 1) {
       // Support blocks with no operands as default to void.
-      addBlockTypeOperand(Operands, NameLoc, WebAssembly::ExprType::Void);
+      addBlockTypeOperand(Operands, NameLoc, WebAssembly::BlockType::Void);
     }
     Parser.Lex();
     return false;
diff --git a/llvm/lib/Target/WebAssembly/Disassembler/LLVMBuild.txt b/llvm/lib/Target/WebAssembly/Disassembler/LLVMBuild.txt
index ab603f20e27..ffa5baa8de4 100644
--- a/llvm/lib/Target/WebAssembly/Disassembler/LLVMBuild.txt
+++ b/llvm/lib/Target/WebAssembly/Disassembler/LLVMBuild.txt
@@ -18,5 +18,5 @@
 type = Library
 name = WebAssemblyDisassembler
 parent = WebAssembly
-required_libraries = WebAssemblyDesc MCDisassembler WebAssemblyInfo Support
+required_libraries = WebAssemblyDesc MCDisassembler WebAssemblyInfo Support MC
 add_to_library_groups = WebAssembly
diff --git a/llvm/lib/Target/WebAssembly/Disassembler/WebAssemblyDisassembler.cpp b/llvm/lib/Target/WebAssembly/Disassembler/WebAssemblyDisassembler.cpp
index f9bf3f85d30..9a9c31cff2d 100644
--- a/llvm/lib/Target/WebAssembly/Disassembler/WebAssemblyDisassembler.cpp
+++ b/llvm/lib/Target/WebAssembly/Disassembler/WebAssemblyDisassembler.cpp
@@ -24,6 +24,7 @@
 #include "llvm/MC/MCInstrInfo.h"
 #include "llvm/MC/MCSubtargetInfo.h"
 #include "llvm/MC/MCSymbol.h"
+#include "llvm/MC/MCSymbolWasm.h"
 #include "llvm/Support/Endian.h"
 #include "llvm/Support/LEB128.h"
 #include "llvm/Support/TargetRegistry.h"
@@ -213,10 +214,29 @@ MCDisassembler::DecodeStatus WebAssemblyDisassembler::getInstruction(
         return MCDisassembler::Fail;
       break;
     }
-    // block_type operands (uint8_t).
+    // block_type operands:
     case WebAssembly::OPERAND_SIGNATURE: {
-      if (!parseImmediate<uint8_t>(MI, Size, Bytes))
+      int64_t Val;
+      uint64_t PrevSize = Size;
+      if (!nextLEB(Val, Bytes, Size, true))
         return MCDisassembler::Fail;
+      if (Val < 0) {
+        // Negative values are single septet value types or empty types
+        if (Size != PrevSize + 1) {
+          MI.addOperand(
+              MCOperand::createImm(int64_t(WebAssembly::BlockType::Invalid)));
+        } else {
+          MI.addOperand(MCOperand::createImm(Val & 0x7f));
+        }
+      } else {
+        // We don't have access to the signature, so create a symbol without one
+        MCSymbol *Sym = getContext().createTempSymbol("typeindex", true);
+        auto *WasmSym = cast<MCSymbolWasm>(Sym);
+        WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
+        const MCExpr *Expr = MCSymbolRefExpr::create(
+            WasmSym, MCSymbolRefExpr::VK_WASM_TYPEINDEX, getContext());
+        MI.addOperand(MCOperand::createExpr(Expr));
+      }
       break;
     }
     // FP operands.
diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyInstPrinter.cpp b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyInstPrinter.cpp
index f7af38459ab..221ac17b833 100644
--- a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyInstPrinter.cpp
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyInstPrinter.cpp
@@ -272,9 +272,21 @@ void WebAssemblyInstPrinter::printWebAssemblyP2AlignOperand(const MCInst *MI,
 void WebAssemblyInstPrinter::printWebAssemblySignatureOperand(const MCInst *MI,
                                                               unsigned OpNo,
                                                               raw_ostream &O) {
-  auto Imm = static_cast<unsigned>(MI->getOperand(OpNo).getImm());
-  if (Imm != wasm::WASM_TYPE_NORESULT)
-    O << WebAssembly::anyTypeToString(Imm);
+  const MCOperand &Op = MI->getOperand(OpNo);
+  if (Op.isImm()) {
+    auto Imm = static_cast<unsigned>(Op.getImm());
+    if (Imm != wasm::WASM_TYPE_NORESULT)
+      O << WebAssembly::anyTypeToString(Imm);
+  } else {
+    auto Expr = cast<MCSymbolRefExpr>(Op.getExpr());
+    auto *Sym = cast<MCSymbolWasm>(&Expr->getSymbol());
+    if (Sym->getSignature()) {
+      O << WebAssembly::signatureToString(Sym->getSignature());
+    } else {
+      // Disassembler does not currently produce a signature
+      O << "unknown_type";
+    }
+  }
 }
 
 // We have various enums representing a subset of these types, use this
diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCCodeEmitter.cpp b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCCodeEmitter.cpp
index 44b6d6a968a..1a4c57e66d2 100644
--- a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCCodeEmitter.cpp
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCCodeEmitter.cpp
@@ -152,6 +152,7 @@ void WebAssemblyMCCodeEmitter::encodeInstruction(
         break;
       case WebAssembly::OPERAND_FUNCTION32:
       case WebAssembly::OPERAND_OFFSET32:
+      case WebAssembly::OPERAND_SIGNATURE:
       case WebAssembly::OPERAND_TYPEINDEX:
       case WebAssembly::OPERAND_GLOBAL:
       case WebAssembly::OPERAND_EVENT:
diff --git a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h
index 6e17693991b..b339860a381 100644
--- a/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h
+++ b/llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyMCTargetDesc.h
@@ -122,16 +122,22 @@ enum TOF {
 namespace llvm {
 namespace WebAssembly {
 
-/// This is used to indicate block signatures.
-enum class ExprType : unsigned {
+/// Used as immediate MachineOperands for block signatures
+enum class BlockType : unsigned {
+  Invalid = 0x00,
   Void = 0x40,
-  I32 = 0x7F,
-  I64 = 0x7E,
-  F32 = 0x7D,
-  F64 = 0x7C,
-  V128 = 0x7B,
-  Exnref = 0x68,
-  Invalid = 0x00
+  I32 = unsigned(wasm::ValType::I32),
+  I64 = unsigned(wasm::ValType::I64),
+  F32 = unsigned(wasm::ValType::F32),
+  F64 = unsigned(wasm::ValType::F64),
+  V128 = unsigned(wasm::ValType::V128),
+  Exnref = unsigned(wasm::ValType::EXNREF),
+  // Multivalue blocks (and other non-void blocks) are only emitted when the
+  // blocks will never be exited and are at the ends of functions (see
+  // WebAssemblyCFGStackify::fixEndsAtEndOfFunction). They also are never made
+  // to pop values off the stack, so the exact multivalue signature can always
+  // be inferred from the return type of the parent function in MCInstLower.
+  Multivalue = 0xffff,
 };
 
 /// Instruction opcodes emitted via means other than CodeGen.
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
index fbccc58b13a..4893ca686c4 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
@@ -315,12 +315,12 @@ void WebAssemblyCFGStackify::placeBlockMarker(MachineBasicBlock &MBB) {
   //   br_on_exn 0, $__cpp_exception
   //   rethrow
   // end_block
-  WebAssembly::ExprType ReturnType = WebAssembly::ExprType::Void;
+  WebAssembly::BlockType ReturnType = WebAssembly::BlockType::Void;
   if (IsBrOnExn) {
     const char *TagName = BrOnExn->getOperand(1).getSymbolName();
     if (std::strcmp(TagName, "__cpp_exception") != 0)
       llvm_unreachable("Only C++ exception is supported");
-    ReturnType = WebAssembly::ExprType::I32;
+    ReturnType = WebAssembly::BlockType::I32;
   }
 
   auto InsertPos = getLatestInsertPos(Header, BeforeSet, AfterSet);
@@ -406,7 +406,7 @@ void WebAssemblyCFGStackify::placeLoopMarker(MachineBasicBlock &MBB) {
   auto InsertPos = getEarliestInsertPos(&MBB, BeforeSet, AfterSet);
   MachineInstr *Begin = BuildMI(MBB, InsertPos, MBB.findDebugLoc(InsertPos),
                                 TII.get(WebAssembly::LOOP))
-                            .addImm(int64_t(WebAssembly::ExprType::Void));
+                            .addImm(int64_t(WebAssembly::BlockType::Void));
 
   // Decide where in Header to put the END_LOOP.
   BeforeSet.clear();
@@ -575,7 +575,7 @@ void WebAssemblyCFGStackify::placeTryMarker(MachineBasicBlock &MBB) {
   MachineInstr *Begin =
       BuildMI(*Header, InsertPos, Header->findDebugLoc(InsertPos),
               TII.get(WebAssembly::TRY))
-          .addImm(int64_t(WebAssembly::ExprType::Void));
+          .addImm(int64_t(WebAssembly::BlockType::Void));
 
   // Decide where in Header to put the END_TRY.
   BeforeSet.clear();
@@ -1129,7 +1129,7 @@ bool WebAssemblyCFGStackify::fixUnwindMismatches(MachineFunction &MF) {
       MachineInstr *NestedTry =
           BuildMI(*MBB, *RangeBegin, RangeBegin->getDebugLoc(),
                   TII.get(WebAssembly::TRY))
-              .addImm(int64_t(WebAssembly::ExprType::Void));
+              .addImm(int64_t(WebAssembly::BlockType::Void));
 
       // Create the nested EH pad and fill instructions in.
       MachineBasicBlock *NestedEHPad = MF.CreateMachineBasicBlock();
@@ -1231,54 +1231,28 @@ void WebAssemblyCFGStackify::fixEndsAtEndOfFunction(MachineFunction &MF) {
   if (MFI.getResults().empty())
     return;
 
-  // TODO: Generalize from value types to function types for multivalue
-  WebAssembly::ExprType RetType;
-  switch (MFI.getResults().front().SimpleTy) {
-  case MVT::i32:
-    RetType = WebAssembly::ExprType::I32;
-    break;
-  case MVT::i64:
-    RetType = WebAssembly::ExprType::I64;
-    break;
-  case MVT::f32:
-    RetType = WebAssembly::ExprType::F32;
-    break;
-  case MVT::f64:
-    RetType = WebAssembly::ExprType::F64;
-    break;
-  case MVT::v16i8:
-  case MVT::v8i16:
-  case MVT::v4i32:
-  case MVT::v2i64:
-  case MVT::v4f32:
-  case MVT::v2f64:
-    RetType = WebAssembly::ExprType::V128;
-    break;
-  case MVT::exnref:
-    RetType = WebAssembly::ExprType::Exnref;
-    break;
-  default:
-    llvm_unreachable("unexpected return type");
-  }
+  // MCInstLower will add the proper types to multivalue signatures based on the
+  // function return type
+  WebAssembly::BlockType RetType =
+      MFI.getResults().size() > 1
+          ? WebAssembly::BlockType::Multivalue
+          : WebAssembly::BlockType(
+                WebAssembly::toValType(MFI.getResults().front()));
 
   for (MachineBasicBlock &MBB : reverse(MF)) {
     for (MachineInstr &MI : reverse(MBB)) {
       if (MI.isPosition() || MI.isDebugInstr())
         continue;
-      if (MI.getOpcode() == WebAssembly::END_BLOCK) {
-        if (MFI.getResults().size() > 1)
-          report_fatal_error("Multivalue block signatures not implemented yet");
-        EndToBegin[&MI]->getOperand(0).setImm(int32_t(RetType));
-        continue;
-      }
-      if (MI.getOpcode() == WebAssembly::END_LOOP) {
-        if (MFI.getResults().size() > 1)
-          report_fatal_error("Multivalue loop signatures not implemented yet");
+      switch (MI.getOpcode()) {
+      case WebAssembly::END_BLOCK:
+      case WebAssembly::END_LOOP:
+      case WebAssembly::END_TRY:
         EndToBegin[&MI]->getOperand(0).setImm(int32_t(RetType));
         continue;
+      default:
+        // Something other than an `end`. We're done.
+        return;
       }
-      // Something other than an `end`. We're done.
-      return;
     }
   }
 }
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyMCInstLower.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyMCInstLower.cpp
index 647e987309f..59c10243c54 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyMCInstLower.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyMCInstLower.cpp
@@ -163,6 +163,21 @@ MCOperand WebAssemblyMCInstLower::lowerSymbolOperand(const MachineOperand &MO,
   return MCOperand::createExpr(Expr);
 }
 
+MCOperand WebAssemblyMCInstLower::lowerTypeIndexOperand(
+    SmallVector<wasm::ValType, 1> &&Returns,
+    SmallVector<wasm::ValType, 4> &&Params) const {
+  auto Signature = std::make_unique<wasm::WasmSignature>(std::move(Returns),
+                                                         std::move(Params));
+  MCSymbol *Sym = Printer.createTempSymbol("typeindex");
+  auto *WasmSym = cast<MCSymbolWasm>(Sym);
+  WasmSym->setSignature(Signature.get());
+  Printer.addSignature(std::move(Signature));
+  WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
+  const MCExpr *Expr =
+      MCSymbolRefExpr::create(WasmSym, MCSymbolRefExpr::VK_WASM_TYPEINDEX, Ctx);
+  return MCOperand::createExpr(Expr);
+}
+
 // Return the WebAssembly type associated with the given register class.
 static wasm::ValType getType(const TargetRegisterClass *RC) {
   if (RC == &WebAssembly::I32RegClass)
@@ -178,6 +193,16 @@ static wasm::ValType getType(const TargetRegisterClass *RC) {
   llvm_unreachable("Unexpected register class");
 }
 
+static void getFunctionReturns(const MachineInstr *MI,
+                               SmallVectorImpl<wasm::ValType> &Returns) {
+  const Function &F = MI->getMF()->getFunction();
+  const TargetMachine &TM = MI->getMF()->getTarget();
+  Type *RetTy = F.getReturnType();
+  SmallVector<MVT, 4> CallerRetTys;
+  computeLegalValueVTs(F, TM, RetTy, CallerRetTys);
+  valTypesFromMVTs(CallerRetTys, Returns);
+}
+
 void WebAssemblyMCInstLower::lower(const MachineInstr *MI,
                                    MCInst &OutMI) const {
   OutMI.setOpcode(MI->getOpcode());
@@ -208,8 +233,6 @@ void WebAssemblyMCInstLower::lower(const MachineInstr *MI,
       if (I < Desc.NumOperands) {
         const MCOperandInfo &Info = Desc.OpInfo[I];
         if (Info.OperandType == WebAssembly::OPERAND_TYPEINDEX) {
-          MCSymbol *Sym = Printer.createTempSymbol("typeindex");
-
           SmallVector<wasm::ValType, 4> Returns;
           SmallVector<wasm::ValType, 4> Params;
 
@@ -228,26 +251,21 @@ void WebAssemblyMCInstLower::lower(const MachineInstr *MI,
 
           // return_call_indirect instructions have the return type of the
           // caller
-          if (MI->getOpcode() == WebAssembly::RET_CALL_INDIRECT) {
-            const Function &F = MI->getMF()->getFunction();
-            const TargetMachine &TM = MI->getMF()->getTarget();
-            Type *RetTy = F.getReturnType();
-            SmallVector<MVT, 4> CallerRetTys;
-            computeLegalValueVTs(F, TM, RetTy, CallerRetTys);
-            valTypesFromMVTs(CallerRetTys, Returns);
-          }
+          if (MI->getOpcode() == WebAssembly::RET_CALL_INDIRECT)
+            getFunctionReturns(MI, Returns);
 
-          auto *WasmSym = cast<MCSymbolWasm>(Sym);
-          auto Signature = std::make_unique<wasm::WasmSignature>(std::move(Returns),
-                                                            std::move(Params));
-          WasmSym->setSignature(Signature.get());
-          Printer.addSignature(std::move(Signature));
-          WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
-
-          const MCExpr *Expr = MCSymbolRefExpr::create(
-              WasmSym, MCSymbolRefExpr::VK_WASM_TYPEINDEX, Ctx);
-          MCOp = MCOperand::createExpr(Expr);
+          MCOp = lowerTypeIndexOperand(std::move(Returns), std::move(Params));
           break;
+        } else if (Info.OperandType == WebAssembly::OPERAND_SIGNATURE) {
+          auto BT = static_cast<WebAssembly::BlockType>(MO.getImm());
+          assert(BT != WebAssembly::BlockType::Invalid);
+          if (BT == WebAssembly::BlockType::Multivalue) {
+            SmallVector<wasm::ValType, 1> Returns;
+            getFunctionReturns(MI, Returns);
+            MCOp = lowerTypeIndexOperand(std::move(Returns),
+                                         SmallVector<wasm::ValType, 4>());
+            break;
+          }
         }
       }
       MCOp = MCOperand::createImm(MO.getImm());
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyMCInstLower.h b/llvm/lib/Target/WebAssembly/WebAssemblyMCInstLower.h
index 2c375a01a7f..d79c54097eb 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyMCInstLower.h
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyMCInstLower.h
@@ -15,6 +15,7 @@
 #ifndef LLVM_LIB_TARGET_WEBASSEMBLY_WEBASSEMBLYMCINSTLOWER_H
 #define LLVM_LIB_TARGET_WEBASSEMBLY_WEBASSEMBLYMCINSTLOWER_H
 
+#include "llvm/BinaryFormat/Wasm.h"
 #include "llvm/MC/MCInst.h"
 #include "llvm/Support/Compiler.h"
 
@@ -33,6 +34,8 @@ class LLVM_LIBRARY_VISIBILITY WebAssemblyMCInstLower {
   MCSymbol *GetGlobalAddressSymbol(const MachineOperand &MO) const;
   MCSymbol *GetExternalSymbolSymbol(const MachineOperand &MO) const;
   MCOperand lowerSymbolOperand(const MachineOperand &MO, MCSymbol *Sym) const;
+  MCOperand lowerTypeIndexOperand(SmallVector<wasm::ValType, 1> &&,
+                                  SmallVector<wasm::ValType, 4> &&) const;
 
 public:
   WebAssemblyMCInstLower(MCContext &ctx, WebAssemblyAsmPrinter &printer)
diff --git a/llvm/test/CodeGen/WebAssembly/multivalue.ll b/llvm/test/CodeGen/WebAssembly/multivalue.ll
index 483e45b687a..877851f6a36 100644
--- a/llvm/test/CodeGen/WebAssembly/multivalue.ll
+++ b/llvm/test/CodeGen/WebAssembly/multivalue.ll
@@ -1,7 +1,7 @@
 ; RUN: llc < %s -asm-verbose=false -verify-machineinstrs -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -mattr=+multivalue | FileCheck %s
 
-; Test that the multivalue attribute is accepted
-; TODO(tlively): implement multivalue
+; Test that the multivalue returns, function types, and block types
+; work as expected.
 
 target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
 target triple = "wasm32-unknown-unknown"
@@ -10,19 +10,33 @@ target triple = "wasm32-unknown-unknown"
 %packed_pair = type <{ i32, i32 }>
 
 ; CHECK-LABEL: pair_ident:
-; CHECK-NEXT: pair_ident (i32, i32) -> (i32, i32)
+; CHECK-NEXT: .functype pair_ident (i32, i32) -> (i32, i32)
 ; CHECK-NEXT: return $0, $1{{$}}
 define %pair @pair_ident(%pair %p) {
   ret %pair %p
 }
 
 ; CHECK-LABEL: packed_pair_ident:
-; CHECK-NEXT: packed_pair_ident (i32, i32) -> (i32, i32)
-; CHECK-nEXT: return $0, $1{{$}}
+; CHECK-NEXT: .functype packed_pair_ident (i32, i32) -> (i32, i32)
+; CHECK-NEXT: return $0, $1{{$}}
 define %packed_pair @packed_pair_ident(%packed_pair %p) {
   ret %packed_pair %p
 }
 
+; CHECK-LABEL: minimal_loop:
+; CHECK-NEXT: .functype minimal_loop (i32) -> (i32, i64)
+; CHECK-NEXT: .LBB{{[0-9]+}}_1:
+; CHECK-NEXT: loop () -> (i32, i64)
+; CHECK-NEXT: br 0{{$}}
+; CHECK-NEXT: .LBB{{[0-9]+}}_2:
+; CHECK-NEXT: end_loop{{$}}
+define {i32, i64} @minimal_loop(i32* %p) {
+entry:
+  br label %loop
+loop:
+  br label %loop
+}
+
 ; CHECK-LABEL: .section .custom_section.target_features
 ; CHECK-NEXT: .int8 1
 ; CHECK-NEXT: .int8 43
diff --git a/llvm/test/MC/Disassembler/WebAssembly/wasm-error.txt b/llvm/test/MC/Disassembler/WebAssembly/wasm-error.txt
index 6468a4f0c18..200ae0db56a 100644
--- a/llvm/test/MC/Disassembler/WebAssembly/wasm-error.txt
+++ b/llvm/test/MC/Disassembler/WebAssembly/wasm-error.txt
@@ -2,8 +2,11 @@
 
 # CHECK: .text
 
-# CHECK: block invalid_type
+# CHECK: block unknown_type
 0x02 0x00
 
+# CHECK: block invalid_type
+0x02 0xff 0x42
+
 # CHECK: br 16 # Invalid depth argument!
 0x0C 0x10
diff --git a/llvm/test/MC/WebAssembly/basic-assembly.s b/llvm/test/MC/WebAssembly/basic-assembly.s
index 6de4cff8a05..17b501b2568 100644
--- a/llvm/test/MC/WebAssembly/basic-assembly.s
+++ b/llvm/test/MC/WebAssembly/basic-assembly.s
@@ -55,6 +55,12 @@ test0:
     block       i64
     block       f32
     block       f64
+    block       () -> (i32, i32)
+    i32.const   1
+    i32.const   2
+    end_block
+    drop
+    drop
     br_table {0, 1, 2}   # 2 entries, default
     end_block            # first entry jumps here.
     i32.const   1
@@ -162,6 +168,12 @@ test0:
 # CHECK-NEXT:      block       i64
 # CHECK-NEXT:      block       f32
 # CHECK-NEXT:      block       f64
+# CHECK-NEXT:      block       () -> (i32, i32)
+# CHECK-NEXT:      i32.const   1
+# CHECK-NEXT:      i32.const   2
+# CHECK-NEXT:      end_block
+# CHECK-NEXT:      drop
+# CHECK-NEXT:      drop
 # CHECK-NEXT:      br_table {0, 1, 2}  # 1: down to label4
 # CHECK-NEXT:                          # 2: down to label3
 # CHECK-NEXT:      end_block           # label5:
diff --git a/llvm/tools/llvm-mc/Disassembler.cpp b/llvm/tools/llvm-mc/Disassembler.cpp
index e2af2e7f2e3..1ddbddfa184 100644
--- a/llvm/tools/llvm-mc/Disassembler.cpp
+++ b/llvm/tools/llvm-mc/Disassembler.cpp
@@ -17,6 +17,7 @@
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCDisassembler/MCDisassembler.h"
 #include "llvm/MC/MCInst.h"
+#include "llvm/MC/MCObjectFileInfo.h"
 #include "llvm/MC/MCRegisterInfo.h"
 #include "llvm/MC/MCStreamer.h"
 #include "llvm/MC/MCSubtargetInfo.h"
@@ -129,13 +130,10 @@ static bool ByteArrayFromString(ByteArrayTy &ByteArray,
   return false;
 }
 
-int Disassembler::disassemble(const Target &T,
-                              const std::string &Triple,
-                              MCSubtargetInfo &STI,
-                              MCStreamer &Streamer,
-                              MemoryBuffer &Buffer,
-                              SourceMgr &SM,
-                              raw_ostream &Out) {
+int Disassembler::disassemble(const Target &T, const std::string &Triple,
+                              MCSubtargetInfo &STI, MCStreamer &Streamer,
+                              MemoryBuffer &Buffer, SourceMgr &SM,
+                              MCContext &Ctx, raw_ostream &Out) {
 
   std::unique_ptr<const MCRegisterInfo> MRI(T.createMCRegInfo(Triple));
   if (!MRI) {
@@ -149,9 +147,6 @@ int Disassembler::disassemble(const Target &T,
     return -1;
   }
 
-  // Set up the MCContext for creating symbols and MCExpr's.
-  MCContext Ctx(MAI.get(), MRI.get(), nullptr);
-
   std::unique_ptr<const MCDisassembler> DisAsm(
     T.createMCDisassembler(STI, Ctx));
   if (!DisAsm) {
diff --git a/llvm/tools/llvm-mc/Disassembler.h b/llvm/tools/llvm-mc/Disassembler.h
index 11b685233ab..dcd8c279c91 100644
--- a/llvm/tools/llvm-mc/Disassembler.h
+++ b/llvm/tools/llvm-mc/Disassembler.h
@@ -22,17 +22,15 @@ class MemoryBuffer;
 class Target;
 class raw_ostream;
 class SourceMgr;
+class MCContext;
 class MCSubtargetInfo;
 class MCStreamer;
 
 class Disassembler {
 public:
-  static int disassemble(const Target &T,
-                         const std::string &Triple,
-                         MCSubtargetInfo &STI,
-                         MCStreamer &Streamer,
-                         MemoryBuffer &Buffer,
-                         SourceMgr &SM,
+  static int disassemble(const Target &T, const std::string &Triple,
+                         MCSubtargetInfo &STI, MCStreamer &Streamer,
+                         MemoryBuffer &Buffer, SourceMgr &SM, MCContext &Ctx,
                          raw_ostream &Out);
 };
 
diff --git a/llvm/tools/llvm-mc/llvm-mc.cpp b/llvm/tools/llvm-mc/llvm-mc.cpp
index 97d507028c1..c23740a3094 100644
--- a/llvm/tools/llvm-mc/llvm-mc.cpp
+++ b/llvm/tools/llvm-mc/llvm-mc.cpp
@@ -517,8 +517,8 @@ int main(int argc, char **argv) {
     break;
   }
   if (disassemble)
-    Res = Disassembler::disassemble(*TheTarget, TripleName, *STI, *Str,
-                                    *Buffer, SrcMgr, Out->os());
+    Res = Disassembler::disassemble(*TheTarget, TripleName, *STI, *Str, *Buffer,
+                                    SrcMgr, Ctx, Out->os());
 
   // Keep output if no errors.
   if (Res == 0) {