[Mesa-dev] [PATCH] ac/nir: implement emit_{imul, umul}_2x32_64 opcodes

[Bas Nieuwenhuizen]

On Tue, Mar 5, 2019 at 10:30 AM Samuel Pitoiset
<samuel.pitoiset at gmail.com> wrote:
>
> Fixes: 58bcebd987b ("spirv: Allow [i/u]mulExtended to use new nir opcode")
> Signed-off-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
> ---
>  src/amd/common/ac_nir_to_llvm.c | 36 +++++++++++++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
>
> diff --git a/src/amd/common/ac_nir_to_llvm.c b/src/amd/common/ac_nir_to_llvm.c
> index af7a95137c2..74ae690e845 100644
> --- a/src/amd/common/ac_nir_to_llvm.c
> +++ b/src/amd/common/ac_nir_to_llvm.c
> @@ -423,6 +423,32 @@ static LLVMValueRef emit_imul_high(struct ac_llvm_context *ctx,
>         return result;
>  }
>
> +static LLVMValueRef emit_umul_2x32_64(struct ac_llvm_context *ctx,
> +                                     LLVMValueRef src0, LLVMValueRef src1)
> +{
> +       LLVMValueRef result[2];
> +
> +       result[0] = LLVMBuildMul(ctx->builder, src0, src1, "");
> +       result[1] = emit_umul_high(ctx, src0, src1);
> +
> +       LLVMValueRef tmp = LLVMGetUndef(ctx->v2i32);

This tmp assignment is dead?
> +       tmp = ac_build_gather_values(ctx, result, 2);
> +       return LLVMBuildBitCast(ctx->builder, tmp, ctx->i64, "");
> +}
> +
> +static LLVMValueRef emit_imul_2x32_64(struct ac_llvm_context *ctx,
> +                                     LLVMValueRef src0, LLVMValueRef src1)
> +{
> +       LLVMValueRef result[2];
> +
> +       result[0] = LLVMBuildMul(ctx->builder, src0, src1, "");
> +       result[1] = emit_imul_high(ctx, src0, src1);

If we do this lowering, why not just set options->lower_mul_2x32_64?

does it result in better code from LLVM if we convert both args to 64
bit and do a 64-bit mul?

> +
> +       LLVMValueRef tmp = LLVMGetUndef(ctx->v2i32);

This tmp assignment is dead?
> +       tmp = ac_build_gather_values(ctx, result, 2);
> +       return LLVMBuildBitCast(ctx->builder, tmp, ctx->i64, "");
> +}
> +
>  static LLVMValueRef emit_bitfield_extract(struct ac_llvm_context *ctx,
>                                           bool is_signed,
>                                           const LLVMValueRef srcs[3])
> @@ -977,6 +1003,16 @@ static void visit_alu(struct ac_nir_context *ctx, const nir_alu_instr *instr)
>                 src[1] = ac_to_integer(&ctx->ac, src[1]);
>                 result = emit_imul_high(&ctx->ac, src[0], src[1]);
>                 break;
> +       case nir_op_umul_2x32_64:
> +               src[0] = ac_to_integer(&ctx->ac, src[0]);
> +               src[1] = ac_to_integer(&ctx->ac, src[1]);
> +               result = emit_umul_2x32_64(&ctx->ac, src[0], src[1]);
> +               break;
> +       case nir_op_imul_2x32_64:
> +               src[0] = ac_to_integer(&ctx->ac, src[0]);
> +               src[1] = ac_to_integer(&ctx->ac, src[1]);
> +               result = emit_imul_2x32_64(&ctx->ac, src[0], src[1]);
> +               break;
>         case nir_op_pack_half_2x16:
>                 result = emit_pack_half_2x16(&ctx->ac, src[0]);
>                 break;
> --
> 2.21.0
>
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