[PATCH] D135195: [WebAssembly][MC] Fix missing `else` after `return` due to type checker bug

[Sam Clegg via Phabricator via llvm-commits]

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Once we are in the `Unreachable` we want to disable type checking, but
we were unconditionally returning `true` here which means we encountered
and error.  Instead we unconditionally return false to signal no error.

Fixes: https://github.com/llvm/llvm-project/issues/56935


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D135195

Files:
  llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmTypeCheck.cpp
  llvm/test/MC/WebAssembly/type-checker-emit-after-unreachable.s


Index: llvm/test/MC/WebAssembly/type-checker-emit-after-unreachable.s
===================================================================
--- /dev/null
+++ llvm/test/MC/WebAssembly/type-checker-emit-after-unreachable.s
@@ -0,0 +1,27 @@
+# We had a regression where an else instruction would be omitted if it followed
+# return (i.e. it was in an unreachable state).
+# See: https://github.com/llvm/llvm-project/issues/56935
+
+# RUN: llvm-mc -triple=wasm32-unknown-unknown < %s | FileCheck %s
+
+foo:
+  .functype foo () -> (i32)
+  i32.const 1
+  if i32
+    i32.const 2
+    return
+  else
+    i32.const 3
+  end_if
+  end_function
+
+# CHECK-LABEL: foo:
+# CHEKC-NEXT: .functype foo () -> (i32)
+# CHEKC-NEXT: i32.const 1
+# CHEKC-NEXT: if i32
+# CHEKC-NEXT: i32.const 2
+# CHEKC-NEXT: return
+# CHEKC-NEXT: else
+# CHEKC-NEXT: i32.const 3
+# CHEKC-NEXT: end_if
+# CHEKC-NEXT: end_function
Index: llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmTypeCheck.cpp
===================================================================
--- llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmTypeCheck.cpp
+++ llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmTypeCheck.cpp
@@ -74,9 +74,9 @@
   // which are mostly not helpful.
   if (TypeErrorThisFunction)
     return true;
-  // If we're currently in unreachable code, we surpress errors as well.
+  // If we're currently in unreachable code, we surpress errors completely.
   if (Unreachable)
-    return true;
+    return false;
   TypeErrorThisFunction = true;
   dumpTypeStack("current stack: ");
   return Parser.Error(ErrorLoc, Msg);


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