[m-rev.] for post-commit review: Fix compatibility issues for the low-level C parallel grades.

[Julien Fischer]

On Mon, 22 Mar 2010, Paul Bone wrote:

> Branches: main, 10.04
>
> Fix a number of errors and warnings in the runtime picked up by GCC 4.x in
> parallel and threadscope grades.
>
> We had been using types with the wrong signedness well calling atomic operations.
> GCC 4.x also picked up an error where #elif was used instead of #else.
>
> While testing these changes on a 32bit system more bugs where found on the i386
> architecture and on AMD brand processors.
>
> runtime/mercury_atomic_ops.h:
> runtime/mercury_atomic_ops.c:
>     Add unsigned variants of the following atomic operations:
>         increment,
>         add,
>         add_and_fetch,
>         dec_and_is_zero,
>
>     Add a signed variant for compare and swap.
>
>     Rename the MR_atomic_dec_<type>_and_is_zero operation to move the type to
>     the end of the name.
>
>     Use volatile storage in the MR_Stats structure.
>
>     A 32bit machine cannot do atomic operations on 64bit values and MR_Stats
>     must use 64bit values.  Therefore 64bit values in the MR_Stats structure
>     are now protected by a lock on 32bit machines.
>
> runtime/mercury_atomic_ops.h:
>     Fix a typeo in the i386 version of MR_atomic_dec_and_is_zero_uint().
>
> runtime/mercury_atomic_ops.c:
>     AMD CPUs do not conform to Intel's specification for being able to
>     extract the CPU clock speed from the brand string.  When we cannot
>     determine the CPU's clock speed then we write out threadscope
>     timestamps in raw clock cycles rather than nanoseconds.
>
>     On i386 machines the ebx register is used to implement PIC code,
>     however the CPUID instruction uses it to output information.  Save
>     this register on C's stack while we issue CPUID and retrieve the
>     result in ebx.
>
>     We now pass native machine sized values to the inline assembler code
>     that implements RDTSC and RDTSCP.
>
>     Fix commenting style in some places.
>
> runtime/mercury_atomic_ops.c:
>     Fix some incorrect C preprocessor code for conditional compilation.
>
> runtime/mercury_grade.h:
>     Increment binary compatibility number.  This should have been done in a
>     prior change when the MR_runnext macro changed which broke binary
>     compatibility in the parallel low-level C grades.
>
> runtime/mercury_context.h:
>     In MR_SyncTerm_Struct use an unsigned value for the number of conjuncts
>     remaining before the conjunction is complete.
>
> runtime/mercury_threadscope.c:
>     Record raw cpu clock ticks rather than milliseconds when we don't
>     know the processor's clock speed.
>
> runtime/mercury_context.c:
> runtime/mercury_wsdeque.h:
> runtime/mercury_wsdeque.c:
>     Conform to changes in mercury_atomic_ops.h

The diff looks okay, although I wonder whether the use of the prefixes
_int and _uint might end up causing confusion between C's int type and
MR_Integer etc.

I would also be interested to now if this fixes the problems with
none.par.gc on eris.

Julien.
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