[WebAssembly] Handle block-like structures consistently in type checker

[aheejin]

Summary

We disable type check in unreachable code, but when the unreachable code
is enclosed within a block-like structure, the block as a whole has a
valid type and we should continue type checking after the block. But it
looks we currently only do that for blocks and not other block-like
structures (loops, trys, and ifs). Also unreachable code within
if's true body shouldn't disable type checking in else body, and
that in try body shouldn't disable type checking in catch/catch_all
body.

This also causes the values/types on the stack to be correctly checked
when encounterint catch, catch_all, and delegate.

[aheejin]

Add one more test

[aheejin]

Test name change

[aheejin]

More

[aheejin]

Fix

[aheejin]

delete newline

[aheejin]

llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmTypeCheck.cpp

313–326

This code is just moved from below

[aheejin]

More

[aheejin]

llvm/test/MC/WebAssembly/type-checker-errors.s

277

This (and another FIXME end_if_type_mismatch_2) is not done even with this patch due to another bug, which I'm planning to fix in another CL.

I renamed these to tests to else_*** to end_if_*** so that else_*** means checking types when we encounter else, and end_if_*** means checking types when we encounter end_if.

[aheejin]

Handle delegate too

[aheejin]

Add one more test

[dschuff]

These are nice improvements!

llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmTypeCheck.cpp

if (popType(ErrorLoc, Type))
       return true;
   } else if (Name == "drop") {
     if (popType(ErrorLoc, {}))
       return true;
   } else if (Name == "end_block" || Name == "end_loop" || Name == "end_if" ||
              Name == "else" || Name == "end_try") {
     if (checkEnd(ErrorLoc, Name == "else"))
       return true;
-    if (Name == "end_block")
+    if (Name.startswith("end_"))
       Unreachable = false;
   } else if (Name == "return") {
     if (endOfFunction(ErrorLoc))
       return true;
   } else if (Name == "call_indirect" || Name == "return_call_indirect") {
     // Function value.
     if (popType(ErrorLoc, wasm::ValType::I32)) return true;
     if (checkSig(ErrorLoc, LastSig)) return true;
     if (Name == "return_call_indirect" && endOfFunction(ErrorLoc))
       return true;
   } else if (Name == "call" || Name == "return_call") {
     const MCSymbolRefExpr *SymRef;
     if (getSymRef(Operands[1]->getStartLoc(), Inst, SymRef))
       return true;
     auto WasmSym = cast<MCSymbolWasm>(&SymRef->getSymbol());
     auto Sig = WasmSym->getSignature();
     if (!Sig || WasmSym->getType() != wasm::WASM_SYMBOL_TYPE_FUNCTION)
       return typeError(Operands[1]->getStartLoc(), StringRef("symbol ") +
                                                        WasmSym->getName() +
                                                        " missing .functype");
     if (checkSig(ErrorLoc, *Sig)) return true;
     if (Name == "return_call" && endOfFunction(ErrorLoc))
       return true;
   } else if (Name == "catch") {
     const MCSymbolRefExpr *SymRef;
     if (getSymRef(Operands[1]->getStartLoc(), Inst, SymRef))
       return true;
     const auto *WasmSym = cast<MCSymbolWasm>(&SymRef->getSymbol());

llvm/test/MC/WebAssembly/type-checker-errors.s

# CHECK: :[[@LINE+1]]:3: error: end got i32, expected f32
   end_function
 
 else_insufficient_values_on_stack:
   .functype else_insufficient_values_on_stack () -> ()
   i32.const 1
   if i32
   i32.const 2
   else
 # FIXME: Should complain about insufficient values on the stack.
   end_if
 # FIXME: Should complain about superflous value on the stack.
   end_function
 
 else_type_mismatch:
   .functype else_type_mismatch () -> ()
   i32.const 1
   if i32

 
 other_insn_test_3:
   .functype other_insn_test_3 () -> ()
   f32.const 1.0
   f32.const 2.0
   f32.add
 # CHECK: :[[@LINE+1]]:3: error: 1 superfluous return values
   end_function
+
+unreachable_within_block:
+  .functype unreachable_within_block () -> ()
+  block
+  unreachable
+  end_block
+# CHECK: :[[@LINE+1]]:3: error: empty stack while popping value
+  drop
+  end_function
+
+unreachable_within_loop:
+  .functype unreachable_within_loop () -> ()
+  loop
+  unreachable
+  end_loop
+# CHECK: :[[@LINE+1]]:3: error: empty stack while popping value
+  drop
+  end_function
+
+unreachable_within_if:
+  .functype unreachable_within_if () -> ()
+  i32.const 0
+  if
+  unreachable
+  else
+  unreachable
+  end_if
+# CHECK: :[[@LINE+1]]:3: error: empty stack while popping value
+  drop
+  end_function
+
+unreachable_within_try:
+  .functype unreachable_within_try () -> ()
+  try
+  unreachable
+  catch_all
+  unreachable
+  end_try
+# CHECK: :[[@LINE+1]]:3: error: empty stack while popping value
+  drop
+  end_function