[wasm][arm] Emit MaybeCheckConstPool in the trap code generation

src/compiler/arm/code-generator-arm.cc

Index: src/compiler/arm/code-generator-arm.cc
diff --git a/src/compiler/arm/code-generator-arm.cc b/src/compiler/arm/code-generator-arm.cc
index 75dea85194876168828cb6d28cdf877d930dda6b..07a35920a63b3e9fa295f63c39e37518cb2a541f 100644
--- a/src/compiler/arm/code-generator-arm.cc
+++ b/src/compiler/arm/code-generator-arm.cc
@@ -2135,6 +2135,8 @@ void CodeGenerator::AssembleArchTrap(Instruction* instr,
 
    private:
     void GenerateCallToTrap(Builtins::Name trap_id) {
+      // Ensure to emit the constant pool first if necessary.
+      __ MaybeCheckConstPool();

[jbramley, 2017/03/07 14:24:08]

What is special about this location? I would have thought that the subsequent
code generation would trigger this check. (The pools aren't blocked.)

If the subsequent code _doesn't_ emit the pool properly, we should work out why
not, because otherwise this crash is probably just a symptom of a different
underlying problem.

       if (trap_id == Builtins::builtin_count) {
         // We cannot test calls to the runtime in cctest/test-run-wasm.
         // Therefore we emit a call to C here instead of a call to the runtime.