In fact, even if user set 'FP_CONTRACT ON', we can also choose not do 'mad optimization.' It depends on us whether or not do the contraction. "Contract on" is just a hint. Obviously contract on will get better speed and accuracy.
I think the compiler_menger_sponge_no_shadow fail because of accuracy. Its reference is got with mad instruction. I think we can use the new result to replace the reference, there should be not too much difference. If they differ too much, then it would be a bug. -----Original Message----- From: Zhigang Gong [mailto:zhigang.g...@linux.intel.com] Sent: Monday, November 04, 2013 3:41 PM To: Song, Ruiling Cc: beignet@lists.freedesktop.org Subject: Re: [Beignet] [PATCH] GBE: disable MulAdd pattern in instruction selection temporarily. This patch breaks utests compiler_menger_sponge_no_shadow. Actually, my first feeling of this patch is that it assumes that FP_CONTRACT is always off and may be cause problem if this assumption is incorrect. The unit test case compiler_menger_sponge_no_shadow should be one of that case. Any thoughts? On Fri, Nov 01, 2013 at 02:16:08PM +0800, Ruiling Song wrote: > The story starts from 'FP_CONTRACT'. In c99 spec, it describes > constract expression as: > "A floating expression may be contracted, that is, evaluated as though > it were an atomic operation, thereby omitting rounding errors implied > by the source code and the expression evaluation method." > > But user can use 'pragma FP_CONTRACT OFF' to disable float > contraction, in which condition, we should not do contraction like mad > optimization. > In SPIR 1.2, named metadata 'opencl.enable.FP_CONTRACT' will be used to do > this. > When Clang is ready, we need refine the backend logic. > > Signed-off-by: Ruiling Song <ruiling.s...@intel.com> > --- > backend/src/backend/gen_insn_selection.cpp | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/backend/src/backend/gen_insn_selection.cpp > b/backend/src/backend/gen_insn_selection.cpp > index 7eae7ca..1f25f0e 100644 > --- a/backend/src/backend/gen_insn_selection.cpp > +++ b/backend/src/backend/gen_insn_selection.cpp > @@ -1856,6 +1856,9 @@ namespace gbe > { > using namespace ir; > > + // XXX TODO: we need a clean support of FP_CONTRACT to remove below > line 'return false' > + // if 'pragma FP_CONTRACT OFF' is used in cl kernel, we should not do > mad optimization. > + return false; > // MAD tend to increase liveness of the sources (since there are three > of > // them). TODO refine this strategy. Well, we should be able at least > to > // evaluate per basic block register pressure and selectively > enable > -- > 1.7.9.5 > > _______________________________________________ > Beignet mailing list > Beignet@lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/beignet _______________________________________________ Beignet mailing list Beignet@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/beignet
