[Beignet] [PATCH] GBE: Refine logic of finding where the local variable is defined.

[Zhigang Gong]

LGTM, pushed with the load/store optimization patch. Everything works fine.
Thanks.

On Fri, May 09, 2014 at 12:54:25PM +0800, Ruiling Song wrote:
> Traverse all uses of the local variable as there maybe some dead use.
> Most time, the function will return fast, as the use tree is not deep.
> 
> Signed-off-by: Ruiling Song <ruiling.song at intel.com>
> ---
>  backend/src/llvm/llvm_gen_backend.cpp |   25 ++++++++++++++-----------
>  1 file changed, 14 insertions(+), 11 deletions(-)
> 
> diff --git a/backend/src/llvm/llvm_gen_backend.cpp b/backend/src/llvm/llvm_gen_backend.cpp
> index 8489c87..c71a17d 100644
> --- a/backend/src/llvm/llvm_gen_backend.cpp
> +++ b/backend/src/llvm/llvm_gen_backend.cpp
> @@ -1402,6 +1402,18 @@ namespace gbe
>    BVAR(OCL_OPTIMIZE_PHI_MOVES, true);
>    BVAR(OCL_OPTIMIZE_LOADI, true);
>  
> +  static const Instruction *getInstructionUseLocal(const Value *v) {
> +    // Local variable can only be used in one kernel function. So, if we find
> +    // one instruction that use the local variable, simply return.
> +    const Instruction *insn = NULL;
> +    for(Value::const_use_iterator iter = v->use_begin(); iter != v->use_end(); ++iter) {
> +      if(isa<Instruction>(*iter)) return cast<const Instruction>(*iter);
> +      insn = getInstructionUseLocal(*iter);
> +      if(insn != NULL) break;
> +    }
> +    return insn;
> +  }
> +
>    void GenWriter::allocateGlobalVariableRegister(Function &F)
>    {
>      // Allocate a address register for each global variable
> @@ -1414,18 +1426,9 @@ namespace gbe
>        ir::AddressSpace addrSpace = addressSpaceLLVMToGen(v.getType()->getAddressSpace());
>        if(addrSpace == ir::MEM_LOCAL) {
>          const Value * val = cast<Value>(&v);
> -        // local variable can only be used in one kernel function. so, don't need to check its all uses.
> -        // loop through the Constant to find the instruction that use the global variable
> -        // FIXME need to find a more grace way to find the function which use this local data.
> -        const Instruction * insn = NULL;
> -        for( Value::const_use_iterator it = val->use_begin(), prev = val->use_begin();
> -             it != prev->use_end() && insn == NULL;
> -             prev = it, it = it->use_begin() )
> -          for( Value::const_use_iterator innerIt = it;
> -               innerIt != val->use_end() && insn == NULL;
> -               innerIt++)
> -            insn = dyn_cast<Instruction>(*innerIt);
> +        const Instruction *insn = getInstructionUseLocal(val);
>          GBE_ASSERT(insn && "Can't find a valid reference instruction for local variable.");
> +
>          const BasicBlock * bb = insn->getParent();
>          const Function * func = bb->getParent();
>          if(func != &F) continue;
> -- 
> 1.7.10.4
> 
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