[Beignet] [PATCH 2/5] GBE: refine liveness analysis.

[Song, Ruiling]

LGTM.
Yes, we current don't use uniform information before instruction selection. So it is OK to disable uniform analysis before insn selection.
But in the long term, we need to enhance our Gen IR, such as introduce more optimization, we may add the uniform information again I think..

Thanks!
Ruiling

> -----Original Message-----
> From: Beignet [mailto:beignet-bounces at lists.freedesktop.org] On Behalf Of
> Zhigang Gong
> Sent: Tuesday, September 1, 2015 12:05 PM
> To: beignet at lists.freedesktop.org
> Cc: Gong, Zhigang
> Subject: [Beignet] [PATCH 2/5] GBE: refine liveness analysis.
> 
> Only in gen backend stage, we need to take care of the special extra liveout and
> uniform analysis. In IR stage, we don't need to handle them.
> 
> Signed-off-by: Zhigang Gong <zhigang.gong at intel.com>
> ---
>  backend/src/backend/context.cpp |  2 +-
>  backend/src/ir/liveness.cpp     | 17 ++++++++++-------
>  backend/src/ir/liveness.hpp     |  2 +-
>  3 files changed, 12 insertions(+), 9 deletions(-)
> 
> diff --git a/backend/src/backend/context.cpp
> b/backend/src/backend/context.cpp index 33b2409..81b284d 100644
> --- a/backend/src/backend/context.cpp
> +++ b/backend/src/backend/context.cpp
> @@ -322,7 +322,7 @@ namespace gbe
>      unit(unit), fn(*unit.getFunction(name)), name(name), liveness(NULL),
> dag(NULL), useDWLabel(false)
>    {
>      GBE_ASSERT(unit.getPointerSize() == ir::POINTER_32_BITS);
> -    this->liveness = GBE_NEW(ir::Liveness, const_cast<ir::Function&>(fn));
> +    this->liveness = GBE_NEW(ir::Liveness,
> + const_cast<ir::Function&>(fn), true);
>      this->dag = GBE_NEW(ir::FunctionDAG, *this->liveness);
>      // r0 (GEN_REG_SIZE) is always set by the HW and used at the end by EOT
>      this->registerAllocator = NULL; //GBE_NEW(RegisterAllocator,
> GEN_REG_SIZE, 4*KB - GEN_REG_SIZE); diff --git a/backend/src/ir/liveness.cpp
> b/backend/src/ir/liveness.cpp index 9fa7ac3..e2240c0 100644
> --- a/backend/src/ir/liveness.cpp
> +++ b/backend/src/ir/liveness.cpp
> @@ -27,7 +27,7 @@
>  namespace gbe {
>  namespace ir {
> 
> -  Liveness::Liveness(Function &fn) : fn(fn) {
> +  Liveness::Liveness(Function &fn, bool isInGenBackend) : fn(fn) {
>      // Initialize UEVar and VarKill for each block
>      fn.foreachBlock([this](const BasicBlock &bb) {
>        this->initBlock(bb);
> @@ -48,12 +48,15 @@ namespace ir {
>      }
>      // extend register (def in loop, use out-of-loop) liveness to the whole loop
>      set<Register> extentRegs;
> -    this->computeExtraLiveInOut(extentRegs);
> -    // analyze uniform values. The extentRegs contains all the values which is
> -    // defined in a loop and use out-of-loop which could not be a uniform. The
> reason
> -    // is that when it reenter the second time, it may active different lanes. So
> -    // reenter many times may cause it has different values in different lanes.
> -    this->analyzeUniform(&extentRegs);
> +    // Only in Gen backend we need to take care of extra live out analysis.
> +    if (isInGenBackend) {
> +      this->computeExtraLiveInOut(extentRegs);
> +      // analyze uniform values. The extentRegs contains all the values which is
> +      // defined in a loop and use out-of-loop which could not be a uniform. The
> reason
> +      // is that when it reenter the second time, it may active different lanes. So
> +      // reenter many times may cause it has different values in different lanes.
> +      this->analyzeUniform(&extentRegs);
> +    }
>    }
> 
>    Liveness::~Liveness(void) {
> diff --git a/backend/src/ir/liveness.hpp b/backend/src/ir/liveness.hpp index
> 4a7dc4e..d9fa2ed 100644
> --- a/backend/src/ir/liveness.hpp
> +++ b/backend/src/ir/liveness.hpp
> @@ -48,7 +48,7 @@ namespace ir {
>    class Liveness : public NonCopyable
>    {
>    public:
> -    Liveness(Function &fn);
> +    Liveness(Function &fn, bool isInGenBackend = false);
>      ~Liveness(void);
>      /*! Set of variables used upwards in the block (before a definition) */
>      typedef set<Register> UEVar;
> --
> 1.9.1
> 
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