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Re: [gomp4 11/14] libgomp: avoid variable-length stack allocation in team.c
- From: Bernd Schmidt <bschmidt at redhat dot com>
- To: Alexander Monakov <amonakov at ispras dot ru>, gcc-patches at gcc dot gnu dot org
- Cc: Jakub Jelinek <jakub at redhat dot com>, Dmitry Melnik <dm at ispras dot ru>
- Date: Tue, 20 Oct 2015 22:45:53 +0200
- Subject: Re: [gomp4 11/14] libgomp: avoid variable-length stack allocation in team.c
- Authentication-results: sourceware.org; auth=none
- References: <1445366076-16082-1-git-send-email-amonakov at ispras dot ru> <1445366076-16082-12-git-send-email-amonakov at ispras dot ru>
On 10/20/2015 08:34 PM, Alexander Monakov wrote:
NVPTX does not support alloca or variable-length stack allocations, thus
heap allocation needs to be used instead. I've opted to make this a generic
change instead of guarding it with an #ifdef: libgomp usually leaves thread
stack size up to libc, so avoiding unbounded stack allocation makes sense.
* task.c (GOMP_task): Use a fixed-size on-stack buffer or a heap
allocation instead of a variable-size on-stack allocation.
+ char buf_fixed[2048], *buf = buf_fixed;
This might also not be the best of ideas on a GPU - the stack size isn't
all that unlimited, what with there being lots of threads. If I do
size_t stack, heap;
cuCtxGetLimit (&stack, CU_LIMIT_STACK_SIZE);
in the nvptx-run program we've used for testing, it shows a default
stack size of just 1kB.
Bernd