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

[Samuel Pitoiset]

On 3/5/19 2:01 PM, Bas Nieuwenhuizen wrote:
> 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?
I will send a v2 with that removed.
>> +       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?
No LLVM differences.
>
>> +
>> +       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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