[PATCH] D147504: [WebAssembly] `AsmTypeCheck` support to br instr

[Congcong Cai via Phabricator via llvm-commits]

HerrCai0907 added inline comments.


================
Comment at: llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmTypeCheck.cpp:448-449
                                                        " missing .tagtype");
-    // catch instruction pushes values whose types are specified in the tag's
-    // "params" part
+    // if nest structure is good, last BrStack is operand stack in try instr;
+    Stack = BrStack.back().getEnterStack();
+    // catch instruction pushes values whose types are specified in the
----------------
aheejin wrote:
> I don't think we should restore try's `EnterStack` here? In a `catch` body, the only input params are the caught values, not the `try`'s input types.
The semantic of catch instructions in `try [T1->T2] catch [T3]` is [T2 -> T3]. 
If we don't restore the stack, we will get a incorrect stack after end_try.
For example
```
.tagtype TAG f32
i32.const 1
try i32
    f32.const 1.0
    throw TAG
    // here ok because unreachable
    drop
catch TAG
    i32.trunc_f32_s
end_try
// here type stack is [i32, i32] but without restore we will get error


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  https://reviews.llvm.org/D147504/new/

https://reviews.llvm.org/D147504