css jit should not save callee saved registers

[Alex Christensen]

We do a lot of pushing and popping that we don't need to, especially on armv7 and x86_64.  This could minimize it.

[Alex Christensen]

Created attachment 233185 [details]
Patch

[Alex Christensen]

Comment on attachment 233185 [details]
Patch

We need a way to specify whether we want to save the values in the argument registers.

[Alex Christensen]

Created attachment 233994 [details]
Patch

[Alex Christensen]

Created attachment 234001 [details]
Patch

[Geoffrey Garen]

Comment on attachment 234001 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=234001&action=review

r=me

> Source/WebCore/cssjit/SelectorCompiler.cpp:1442
>      // FIXME: We should look into doing something smart in MacroAssembler instead.
>      Assembler::Address flagAddress(childStyle, RenderStyle::noninheritedFlagsMemoryOffset() + RenderStyle::NonInheritedFlags::flagsMemoryOffset());
>  #if CPU(ARM_THUMB2)
> -    m_assembler.or32(Assembler::TrustedImm32(newFlag & 0xffffffff), flagAddress);
> -    Assembler::Address flagHighBits = flagAddress.withOffset(4);
> -    m_assembler.or32(Assembler::TrustedImm32(newFlag >> 32), flagHighBits);
> +    int32_t flagLowBits = newFlag & 0xffffffff;
> +    int32_t flagHighBits = newFlag >> 32;
> +    if (flagLowBits)
> +        m_assembler.or32(Assembler::TrustedImm32(flagLowBits), flagAddress);
> +    if (flagHighBits) {
> +        Assembler::Address flagHighAddress = flagAddress.withOffset(4);
> +        m_assembler.or32(Assembler::TrustedImm32(flagHighBits), flagHighAddress);
> +    }

A good optimization, but probably better as a separate patch, since the topic is not related to register saving.

[Alex Christensen]

http://trac.webkit.org/changeset/170548