Hi Julian! On 2019-11-28T14:24:02+0000, Julian Brown <jul...@codesourcery.com> wrote: > As mentioned in PR91985, offloading compilation is broken at present > because of an issue with LTO streaming. With thanks to Joseph for > hints, here's a solution. > > Unlike e.g. the _FloatN types, when decimal floating-point types are > enabled, common tree nodes are created for each float type size (e.g. > dfloat32_type_node) and also a pointer to each type is created > (e.g. dfloat32_ptr_type_node). tree-streamer.c:record_common_node emits > these like: > > <float:32> (dfloat32_type_node) > <float:64> (dfloat64_type_node) > <float:128> (dfloat128_type_node) > <float:32> * (dfloat32_ptr_type_node) > <float:32> > <float:64> * (dfloat64_ptr_type_node) > <float:64> > <float:128> * (dfloat128_ptr_type_node) > <float:128> > > I.e., with explicit emission of a copy of the pointed-to type following > the pointer itself.
I also do see that, but I fail to understand why that duplication: the
first '<float:32>' and the second one (after the '<float:32> *') are the
same node, or aren't they?
> When DFP is disabled, we instead get:
>
> <<< error >>>
> <<< error >>>
> <<< error >>>
> <<< error >>>
> <<< error >>>
> <<< error >>>
(With that expectedly being any 'NULL_TREE's converted to
'error_mark_node' in 'gcc/tree-streamer.c:record_common_node'.)
> So, the number of nodes emitted during LTO write-out in the host/read-in
> in the offload compiler do not match.
ACK.
> This patch restores the number of nodes emitted by creating
> dfloatN_ptr_type_node as generic pointers rather than treating them as
> flat error_type_nodes. I don't think there's an easy way of creating an
> "error_type_node *", nor do I know if that would really be preferable.
>
> Tested with offloading to NVPTX & bootstrapped. OK to apply?
> commit 17119773a8a45af098364b4faafe68f2e868479a
> Author: Julian Brown <jul...@codesourcery.com>
> Date: Wed Nov 27 18:41:56 2019 -0800
>
> Fix decimal floating-point LTO streaming for offloading compilation
>
> gcc/
> * tree.c (build_common_tree_nodes): Use pointer type for
> dfloat32_ptr_type_node, dfloat64_ptr_type_node and
> dfloat128_ptr_type_node when decimal floating point support is
> disabled.
>
> diff --git a/gcc/tree.c b/gcc/tree.c
> index 5ae250ee595..db3f225ea7f 100644
> --- a/gcc/tree.c
> +++ b/gcc/tree.c
> @@ -10354,6 +10354,15 @@ build_common_tree_nodes (bool signed_char)
> layout_type (dfloat128_type_node);
> dfloat128_ptr_type_node = build_pointer_type (dfloat128_type_node);
> }
> + else
> + {
> + /* These must be pointers else tree-streamer.c:record_common_node will
> emit
> + a different number of nodes depending on DFP availability, which breaks
> + offloading compilation. */
> + dfloat32_ptr_type_node = ptr_type_node;
> + dfloat64_ptr_type_node = ptr_type_node;
> + dfloat128_ptr_type_node = ptr_type_node;
> + }
>
> complex_integer_type_node = build_complex_type (integer_type_node, true);
> complex_float_type_node = build_complex_type (float_type_node, true);
(Maybe that's indeed better than my "hamfisted" patch.) ;-)
But it still reads a bit like a workaround (explicitly setting only
'dfloat*_ptr_type_node' here, leaving the actual 'dfloat*_type_node'
untouched (and then later on implicitly converted to 'error_mark_node' as
mentioned).
I guess we need somebody with more experience to review this.
Grüße
Thomas
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