[Beignet] [PATCH 1/2] GBE: optimize SUB dst, imm, src1 instruction.

[Zhigang Gong]

Ping for review.

On Wed, May 14, 2014 at 04:11:26PM +0800, Zhigang Gong wrote:
> We could easily convert it to SUB dst, -src1, -imm.
> Thus we can avoid one LOADI instruction eventually.
> 
> Signed-off-by: Zhigang Gong <zhigang.gong at intel.com>
> ---
>  backend/src/backend/gen_insn_selection.cpp | 30 +++++++++++++++++-------------
>  1 file changed, 17 insertions(+), 13 deletions(-)
> 
> diff --git a/backend/src/backend/gen_insn_selection.cpp b/backend/src/backend/gen_insn_selection.cpp
> index adf523c..a554ee9 100644
> --- a/backend/src/backend/gen_insn_selection.cpp
> +++ b/backend/src/backend/gen_insn_selection.cpp
> @@ -1665,18 +1665,19 @@ namespace gbe
>      return false;
>    }
>  
> -  GenRegister getRegisterFromImmediate(ir::Immediate imm)
> +  GenRegister getRegisterFromImmediate(ir::Immediate imm, bool negate = false)
>    {
>      using namespace ir;
> +    int sign = negate ? -1 : 1;
>      switch (imm.type) {
> -      case TYPE_U32:   return GenRegister::immud(imm.data.u32);
> -      case TYPE_S32:   return GenRegister::immd(imm.data.s32);
> -      case TYPE_FLOAT: return GenRegister::immf(imm.data.f32);
> -      case TYPE_U16: return GenRegister::immuw(imm.data.u16);
> -      case TYPE_S16: return  GenRegister::immw(imm.data.s16);
> -      case TYPE_U8:  return GenRegister::immuw(imm.data.u8);
> -      case TYPE_S8:  return GenRegister::immw(imm.data.s8);
> -      case TYPE_DOUBLE: return GenRegister::immdf(imm.data.f64);
> +      case TYPE_U32:   return GenRegister::immud(imm.data.u32 * sign);
> +      case TYPE_S32:   return GenRegister::immd(imm.data.s32 * sign);
> +      case TYPE_FLOAT: return GenRegister::immf(imm.data.f32 * sign);
> +      case TYPE_U16: return GenRegister::immuw(imm.data.u16 * sign);
> +      case TYPE_S16: return  GenRegister::immw(imm.data.s16 * sign);
> +      case TYPE_U8:  return GenRegister::immuw(imm.data.u8 * sign);
> +      case TYPE_S8:  return GenRegister::immw(imm.data.s8 * sign);
> +      case TYPE_DOUBLE: return GenRegister::immdf(imm.data.f64 * sign);
>        case TYPE_BOOL: return GenRegister::immuw(-imm.data.b);  //return 0xffff when true
>        default: NOT_SUPPORTED; return GenRegister::immuw(0);
>      }
> @@ -1969,11 +1970,14 @@ namespace gbe
>          if (dag0) dag0->isRoot = 1;
>        }
>        // Left source cannot be immediate but it is OK if we can commute
> -      else if (OCL_OPTIMIZE_IMMEDIATE && dag0 != NULL && insn.commutes() && dag0->insn.getOpcode() == OP_LOADI &&
> -               canGetRegisterFromImmediate(dag0->insn) && type != TYPE_BOOL) {
> +      else if (OCL_OPTIMIZE_IMMEDIATE && dag0 != NULL &&
> +               (insn.commutes() || insn.getOpcode() == OP_SUB) &&
> +               dag0->insn.getOpcode() == OP_LOADI && canGetRegisterFromImmediate(dag0->insn) &&
> +               type != TYPE_BOOL) {
>          const auto &childInsn = cast<LoadImmInstruction>(dag0->insn);
> -        src0 = sel.selReg(insn.getSrc(1), type);
> -        src1 = getRegisterFromImmediate(childInsn.getImmediate());
> +        src0 = insn.getOpcode() != OP_SUB ?
> +               sel.selReg(insn.getSrc(1), type) : GenRegister::negate(sel.selReg(insn.getSrc(1), type));
> +        src1 = getRegisterFromImmediate(childInsn.getImmediate(), insn.getOpcode() == OP_SUB); 
>          if (dag1) dag1->isRoot = 1;
>        }
>        // Just grab the two sources
> -- 
> 1.8.3.2
> 
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