[WebAssembly][MC] Allow empty assembly functions

Differential Revision: https://reviews.llvm.org/D66434

llvm-svn: 369292

2 files changed, 23 insertions, 9 deletions

diff --git a/llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp b/llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp
index da868e59c5f..bfa16a71e11 100644
--- a/llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp
+++ b/llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmParser.cpp
@@ -489,6 +489,7 @@ public:
       if (pop(Name, Block))
         return true;
     } else if (Name == "end_function") {
+      ensureLocals(getStreamer());
       CurrentState = EndFunction;
       if (pop(Name, Function) || ensureEmptyNestingStack())
         return true;
@@ -758,6 +759,19 @@ public:
     return true; // We didn't process this directive.
   }
 
+  // Called either when the first instruction is parsed of the function ends.
+  void ensureLocals(MCStreamer &Out) {
+    if (CurrentState == FunctionStart) {
+      // We haven't seen a .local directive yet. The streamer requires locals to
+      // be encoded as a prelude to the instructions, so emit an empty list of
+      // locals here.
+      auto &TOut = reinterpret_cast<WebAssemblyTargetStreamer &>(
+          *Out.getTargetStreamer());
+      TOut.emitLocal(SmallVector<wasm::ValType, 0>());
+      CurrentState = FunctionLocals;
+    }
+  }
+
   bool MatchAndEmitInstruction(SMLoc IDLoc, unsigned & /*Opcode*/,
                                OperandVector &Operands, MCStreamer &Out,
                                uint64_t &ErrorInfo,
@@ -768,15 +782,7 @@ public:
         MatchInstructionImpl(Operands, Inst, ErrorInfo, MatchingInlineAsm);
     switch (MatchResult) {
     case Match_Success: {
-      if (CurrentState == FunctionStart) {
-        // This is the first instruction in a function, but we haven't seen
-        // a .local directive yet. The streamer requires locals to be encoded
-        // as a prelude to the instructions, so emit an empty list of locals
-        // here.
-        auto &TOut = reinterpret_cast<WebAssemblyTargetStreamer &>(
-            *Out.getTargetStreamer());
-        TOut.emitLocal(SmallVector<wasm::ValType, 0>());
-      }
+      ensureLocals(Out);
       // Fix unknown p2align operands.
       auto Align = WebAssembly::GetDefaultP2AlignAny(Inst.getOpcode());
       if (Align != -1U) {
diff --git a/llvm/test/MC/WebAssembly/basic-assembly.s b/llvm/test/MC/WebAssembly/basic-assembly.s
index ac01dca3755..6de4cff8a05 100644
--- a/llvm/test/MC/WebAssembly/basic-assembly.s
+++ b/llvm/test/MC/WebAssembly/basic-assembly.s
@@ -2,6 +2,11 @@
 # Check that it converts to .o without errors, but don't check any output:
 # RUN: llvm-mc -triple=wasm32-unknown-unknown -filetype=obj -mattr=+atomics,+unimplemented-simd128,+nontrapping-fptoint,+exception-handling -o %t.o < %s
 
+
+empty_func:
+    .functype empty_func () -> ()
+    end_function
+
 test0:
     # Test all types:
     .functype   test0 (i32, i64) -> (i32)
@@ -111,6 +116,9 @@ test0:
     .globaltype __stack_pointer, i32
 
 # CHECK:           .text
+# CHECK-LABEL: empty_func:
+# CHECK-NEXT:      .functype	empty_func () -> ()
+# CHECK-NEXT:      end_function
 # CHECK-LABEL: test0:
 # CHECK-NEXT:      .functype   test0 (i32, i64) -> (i32)
 # CHECK-NEXT:      .eventtype  __cpp_exception i32