[PATCH, PR69599] Fix GOMP/GOACC_parallel optimization in ipa-pta

[Tom de Vries]

Hi,

when compiling the fipa-pta tests in the libgomp testsuite 
(omp-nested-2.c, pr46032.c) with -flto -flto-partition=max, the tests 
fail in execution (PR69599).

The problem is related to the GOMP/GOACC_parallel optimization we do in 
fipa-pta, where we interpret a call GOMP_parallel (&foo._0, data) as a 
call foo._0 (data).

The problem is that this optimization is only legal in lto if both:
- foo containing the call GOMP_parallel (&foo._0, data) and
- foo._0
are contained in the same partition.

In the case of -flto-partition=max, foo is contained in it's own 
partition, and foo._0 is contained in another partition.  This means the 
data argument to the GOMP_parallel call appears unused, and the setting 
of the argument is optimized away, which causes the execution failure.

This patch fixes that by testing if foo and foo._0 are part of the same 
partition.

[ Note that the node_address_taken change in the patch has no effect, 
since nonlocal_p already tests for used_from_other_partition. But I 
thought it was clearer to state the conditions under which we are 
allowed to ignore node->address_taken explicitly. ]

Bootstrapped and reg-tested on x86_64.

Build for nvidia accelerator and reg-tested libgomp with various lto 
settings.

OK for trunk, stage4?

Thanks,
- Tom
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