Update constant pool correctly when resuming a generator

src/arm/full-codegen-arm.cc

Index: src/arm/full-codegen-arm.cc
diff --git a/src/arm/full-codegen-arm.cc b/src/arm/full-codegen-arm.cc
index c221a4835136ba89054a80207a49f07d223636c2..cc45e6da9f9eb73683510219c0d99350e9c0ba7b 100644
--- a/src/arm/full-codegen-arm.cc
+++ b/src/arm/full-codegen-arm.cc
@@ -2194,12 +2194,20 @@ void FullCodeGenerator::EmitGeneratorResume(Expression *generator,
     __ cmp(r3, Operand(0));
     __ b(ne, &slow_resume);
     __ ldr(r3, FieldMemOperand(r4, JSFunction::kCodeEntryOffset));
+
+    ConstantPoolUnavailableScope constant_pool_unavailable(masm_);

[ulan, 2014/03/11 13:07:39]

Shouldn't this scope be
- at the beginning of the "if (resume_mode == JSGeneratorObject::NEXT)" branch?
- or inside the "if (FLAG_enable_ool_constant_pool)" branch?

[rmcilroy, 2014/03/11 16:14:53]

The Constant Pool is unavailable (for this code object) from the ldr(pp, ...) 
until the Jump(r3) instruction (since between these instructions it contains the
pp for the target function).  

I can't put it inside the "if (FLAG_enable_ool_constant_pool) because the scope
would go out of scope before the Jump(r3).  I could put it at the beginning of
the if (resume_mode == JSGeneratorObject::NEXT) scope if you prefer, but I put
it here to make it clear that this was related to the ldr(pp, ..) instruction. 
If you still prefer moving it to the beginning of the scope though I'm happy to
move it. WDYT?

[ulan, 2014/03/11 16:19:57]

I see, thanks for explaining! What about putting instructions from ldr(pp, ...) 
until the Jump(r3) into a new block { }? That would make clear when exactly the
scope is active.

[rmcilroy, 2014/03/11 16:42:23]

Good call! Done.

+    if (FLAG_enable_ool_constant_pool) {
+      // Load the new code object's constant pool pointer.
+      __ ldr(pp, MemOperand(r3, Code::kConstantPoolOffset - Code::kHeaderSize));
+    }
+
     __ ldr(r2, FieldMemOperand(r1, JSGeneratorObject::kContinuationOffset));
     __ SmiUntag(r2);
     __ add(r3, r3, r2);
     __ mov(r2, Operand(Smi::FromInt(JSGeneratorObject::kGeneratorExecuting)));
     __ str(r2, FieldMemOperand(r1, JSGeneratorObject::kContinuationOffset));
     __ Jump(r3);
+
     __ bind(&slow_resume);
   }