On 22 January 2024 21:33:17 CET, Kwok Cheung Yeung <k...@codesourcery.com>
wrote:
>Hi
>
>There was a bug in the declare-target-indirect-2.c libgomp testcase (testing
>indirect calls in offloaded target regions, spread over multiple
>teams/threads) that due to an errant fallthrough in a switch statement
>resulted in only one indirect function ever getting called:
>
>switch (i % 3)
> {
> case 0: fn_ptr[i] = &foo; // Missing break
> case 1: fn_ptr[i] = &bar; // Missing break
> case 2: fn_ptr[i] = &baz;
> }
>
>However, when the missing break statements are added, the testcase fails with
>an invalid memory access. Upon investigation, this is due to the use of a
>splay-tree as the lookup structure for indirect addresses, as the splay-tree
>moves frequently accessed elements closer to the root node and so needs
>locking when used from multiple threads. However, this would end up partially
>serialising all the threads and kill performance. I have switched the lookup
>structure from a splay tree to a hashtab instead to avoid locking during
>lookup.
>
>I have also tidied up the initialisation of the lookup table by calling it
>only from the first thread of the first team, instead of redundantly calling
>it from every thread and only having the first one reached do the
>initialisation. This removes the need for locking during initialisation.
>
>Tested with offloading to NVPTX and GCN with a x86_64 host. Okay for master?
Can you please akso update the comments to talk about hashtab instead of splay?
TIA
>
>Thanks
>
>Kwok
