RFR, XS, 7120448, Fix FP values for compiled frames in frame::describe
vladimir.kozlov at oracle.com
Tue Jan 17 09:30:56 PST 2012
I think it looks good.
Small note, we need to start updating Copyright year to 2012.
Bertrand Delsart wrote:
> Here is simple review for the first of a series of fixes and
> extensions for frame::describe.
> This is the first of a series of fixes and extensions for
> frame::describe() was calling the platform dependent frame::fp() to
> get the frame pointer. Unfortunately, the semantic of frame::fp() is
> not clearly defined. On compiled x86 frames, the value could be
> arbitrary. That could cause frame::describe to dump misleading
> information and useless memory slots.
> Defined a new frame::real_fp() with a more precise semantic for
> portable shared code.
> This is the value expected by the platform ABI when it defines a frame
> pointer register. It may differ from the effective value of the FP
> register when that register is used in the JVM for other purposes
> (like compiled frames on some platforms). On other platforms, it is
> defined so that the stack area used by this frame goes from real_fp()
> to sp().
> By default, the new definition is equivalent to the old frame::fp()
> definition. x86 is the only OpenJDK supported platform which required
> a different definition.
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