[Mesa-dev] [PATCH] r600g: fix and optimize tgsi_cmp when using ABS and NEG modifier

[Dave Airlie]

On 28 March 2016 at 19:52,  <siro at das-labor.org> wrote:
> From: Patrick Rudolph <siro at das-labor.org>
>
> Some apps set NEG and ABS on the source param to test for zero.
> Use ALU_OP3_CNDE insted of ALU_OP3_CNDGE and unset both modifiers.
>
> It also removes the need for a MOV instruction, as ABS isn't
> supported on op3.
>
> Tested on AMD CAYMAN and AMD RV770.
>
> Signed-off-by: Patrick Rudolph <siro at das-labor.org>

Seems sane to me, does this help in any app in particular?

Reviewed-by: Dave Airlie <airlied at redhat.com>

I just have to remember to push this tomorrow.

Dave.

> ---
>  src/gallium/drivers/r600/r600_shader.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/src/gallium/drivers/r600/r600_shader.c b/src/gallium/drivers/r600/r600_shader.c
> index 77658f5..e5e2e3f 100644
> --- a/src/gallium/drivers/r600/r600_shader.c
> +++ b/src/gallium/drivers/r600/r600_shader.c
> @@ -7707,6 +7707,15 @@ static int tgsi_cmp(struct r600_shader_ctx *ctx)
>         int i, r, j;
>         int lasti = tgsi_last_instruction(inst->Dst[0].Register.WriteMask);
>         int temp_regs[3];
> +       unsigned op;
> +
> +       if (ctx->src[0].abs && ctx->src[0].neg) {
> +               op = ALU_OP3_CNDE;
> +               ctx->src[0].abs = 0;
> +               ctx->src[0].neg = 0;
> +       } else {
> +               op = ALU_OP3_CNDGE;
> +       }
>
>         for (j = 0; j < inst->Instruction.NumSrcRegs; j++) {
>                 temp_regs[j] = 0;
> @@ -7719,7 +7728,7 @@ static int tgsi_cmp(struct r600_shader_ctx *ctx)
>                         continue;
>
>                 memset(&alu, 0, sizeof(struct r600_bytecode_alu));
> -               alu.op = ALU_OP3_CNDGE;
> +               alu.op = op;
>                 r = tgsi_make_src_for_op3(ctx, temp_regs[0], i, &alu.src[0], &ctx->src[0]);
>                 if (r)
>                         return r;
> --
> 2.5.0
>
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