[m-rev.] for review: only reserve 2 registers for global register on x86
Julien Fischer
juliensf at csse.unimelb.edu.au
Fri Nov 9 16:22:12 AEDT 2007
On Thu, 8 Nov 2007, Julien Fischer wrote:
> Estimated hours taken: 1
> Branches: main
>
> As discussed on mercury-developers, reduce the number of registers that
> are reserved for use as gcc global register variables on x86 machines
> for non-PIC Mercury code from three to two.
>
> This change should reduce the frequency of register allocation problems
> occurring with gcc on x86 machines, at the cost of increasing execution
> time for non-PIC by about 2.2%. (That figure is based on our standard
> benchmark.)
>
> runtime/machdeps/i386_regs.h:
> Do not reserve an extra register for use as a global register
> variable for non-PIC on x86.
>
> configure.in:
> Conform to the new number of global register variables.
>
> Define EXT_FOR_LINK_WITH_PIC_OBJECTS as .o rather than .lpic_o
> on x86. (The latter should only be used when MR_PIC_REG has
> some meaning.)
>
> compiler/compile_target_code.m:
> Update a comment: MR_PIC_REG no longer has an effect on x86
> machines.
Could somebody please review this? I would like to commit it today.
Julien.
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