Bug 152337 – Add "explicit operator bool" to ScratchRegisterAllocator::PreservedState

• Component: JavaScriptCore
• Status: RESOLVED FIXED

[Saam Barati]

We should assert we only get valid PreservedStates in restore reused registers.

[Saam Barati]

Created attachment 267460 [details]
patch

[Mark Lam]

Comment on attachment 267460 [details]
patch

r=me

[Darin Adler]

Comment on attachment 267460 [details]
patch

View in context: https://bugs.webkit.org/attachment.cgi?id=267460&action=review

> Source/JavaScriptCore/jit/ScratchRegisterAllocator.cpp:130
> +    RELEASE_ASSERT(!!preservedState);

Really surprised that we need !! here. I think that means there is something wrong with the RELEASE_ASSERT macro.

> Source/JavaScriptCore/jit/ScratchRegisterAllocator.h:82
> +        explicit operator bool() const { return numberOfBytesPreserved != std::numeric_limits<unsigned>::max(); }

I am interested to learn that this is sufficient by itself without also defining operator! for the class. I think this means we can remove many of our operator! definitions throughout the WebKit project.

[Saam Barati]

Comment on attachment 267460 [details]
patch

View in context: https://bugs.webkit.org/attachment.cgi?id=267460&action=review

>> Source/JavaScriptCore/jit/ScratchRegisterAllocator.cpp:130
>> +    RELEASE_ASSERT(!!preservedState);
> 
> Really surprised that we need !! here. I think that means there is something wrong with the RELEASE_ASSERT macro.

We don't. I just do this for stylistic reasons (or lack thereof).
I happen to like the explicitness of how !! looks when testing the truthiness of something. This is probably overkill inside an assert.

>> Source/JavaScriptCore/jit/ScratchRegisterAllocator.h:82
>> +        explicit operator bool() const { return numberOfBytesPreserved != std::numeric_limits<unsigned>::max(); }
> 
> I am interested to learn that this is sufficient by itself without also defining operator! for the class. I think this means we can remove many of our operator! definitions throughout the WebKit project.

I think one of the main benefits of "explicit operator bool" is that it eliminates most of the need for operator!.

[Saam Barati]

landed in:
http://trac.webkit.org/changeset/194158