[Beignet] [PATCH] GBE: don't always treat a multiple destination instruction as root.

[Yang, Rong R]

LGTM, thanks.

> -----Original Message-----
> From: Beignet [mailto:beignet-bounces at lists.freedesktop.org] On Behalf Of
> Zhigang Gong
> Sent: Monday, December 15, 2014 11:58
> To: beignet at lists.freedesktop.org
> Cc: Gong, Zhigang
> Subject: [Beignet] [PATCH] GBE: don't always treat a multiple destination
> instruction as root.
> 
> Don't know why we set this type of instruction as root. It doesn't make sense.
> For example, if we have a read_imagei() to read some data to a int4 value
> and then never use these 4 value, we definitely don't need to generate this
> instruction.
> 
> Signed-off-by: Zhigang Gong <zhigang.gong at intel.com>
> ---
>  backend/src/backend/gen_insn_selection.cpp | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/backend/src/backend/gen_insn_selection.cpp
> b/backend/src/backend/gen_insn_selection.cpp
> index 7ea2498..adff091 100644
> --- a/backend/src/backend/gen_insn_selection.cpp
> +++ b/backend/src/backend/gen_insn_selection.cpp
> @@ -1464,14 +1464,13 @@ namespace gbe
>    } selectionLibraryInitializer;
> 
>    bool Selection::Opaque::isRoot(const ir::Instruction &insn) const {
> -    if (insn.getDstNum() > 1 ||
> -        insn.hasSideEffect() ||
> +    if (insn.hasSideEffect() ||
>          insn.isMemberOf<ir::BranchInstruction>() ||
>          insn.isMemberOf<ir::LabelInstruction>())
>      return true;
> 
>      // No side effect, not a branch and no destination? Impossible
> -    GBE_ASSERT(insn.getDstNum() == 1);
> +    GBE_ASSERT(insn.getDstNum() >= 1);
> 
>      // Root if alive outside the block.
>      // XXX we should use Value and not registers in liveness info
> --
> 1.8.3.2
> 
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