[Beignet] [PATCH] GBE: Fix a bug in encoding MATH instruction

[Zhigang Gong]

Nice catch. I will push it latter.

And, if you have such a unit test case can hit this bug, please
also submit it here. Thanks.

On Mon, Jun 24, 2013 at 10:53:57AM +0800, Ruiling Song wrote:
> For std::vector, a push_back may cause memory relocation if no enough
> memory in the vector pool. And iterator or pointer got previously will
> become invalid after relocation.
> 
> Here in GenEncoder::next(), which will call push_back(), memory
> relocation may occur. Then relocation will make 'insn' point to
> invalid memory that does not belong to GenEncoder::store anymore.
> Then, the setting of execution_width will fail.
> 
> Signed-off-by: Ruiling Song <ruiling.song at intel.com>
> ---
>  backend/src/backend/gen_encoder.cpp |    5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/backend/src/backend/gen_encoder.cpp b/backend/src/backend/gen_encoder.cpp
> index 3d8afe8..ae981b2 100644
> --- a/backend/src/backend/gen_encoder.cpp
> +++ b/backend/src/backend/gen_encoder.cpp
> @@ -1010,7 +1010,9 @@ namespace gbe
>  
>       if (function == GEN_MATH_FUNCTION_INT_DIV_QUOTIENT ||
>           function == GEN_MATH_FUNCTION_INT_DIV_REMAINDER) {
> -        if(insn->header.execution_size == GEN_WIDTH_16) {
> +        insn->header.execution_size = GEN_WIDTH_8;
> +
> +        if(this->curr.execWidth == 16) {
>            GenInstruction *insn2 = this->next(GEN_OPCODE_MATH);
>            GenRegister new_dest, new_src0, new_src1;
>            new_dest = GenRegister::QnPhysical(dst, 1);
> @@ -1024,7 +1026,6 @@ namespace gbe
>            this->setSrc1(insn2, new_src1);
>          }
>  
> -        insn->header.execution_size = GEN_WIDTH_8;
>       }
>    }
>  
> -- 
> 1.7.9.5
> 
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