[asm.js] [wasm] Store function start position for stack check

src/wasm/function-body-decoder.cc

Index: src/wasm/function-body-decoder.cc
diff --git a/src/wasm/function-body-decoder.cc b/src/wasm/function-body-decoder.cc
index d54248392801ccc8672aaf209fe50dfdfcf6ac0b..5c6ec83585fe404d534264bfd7c41d2715bc787b 100644
--- a/src/wasm/function-body-decoder.cc
+++ b/src/wasm/function-body-decoder.cc
@@ -551,7 +551,9 @@ class WasmFullDecoder : public WasmDecoder {
     ssa_env->effect = start;
     SetEnv("initial", ssa_env);
     if (builder_) {
-      builder_->StackCheck(position());
+      // The function-prologue stack check is associated with position 0, which
+      // is never a position of any instruction in the function.
+      builder_->StackCheck(0);
     }
   }