On 03/20/2015 01:58 PM, Ian Romanick wrote:
> From: Ian Romanick <ian.d.roman...@intel.com>
>
> Convert cases like (x * bool(b)) to 'mix(0, x, b)'.
>
> Note: This may hurt the code generated for GPUs that represent Boolean
> values using floating point. shader-db doesn't play well with i915, so
> I haven't been able to check it.
>
> On at least BDW shaders/warsow/85.shader_test is hurt by about 10%, so
> that may be worth investigating.
I think I've found the problem caused here. There's one pattern in the
shader that used to end up with some MADs (4 instructions total), but
now it gets a small pile of hurt (6 instructions total). And the shader
contains that same pattern 14 times in a row. 28 instructions is on the
right order of magnitude of the regression that I saw.
I have a couple ideas to fix this in the backend. Watch for a patch on
Monday or Tuesday.
> v2: Use swizzle_if_required on opeands. Fixes
> arb_texture_buffer_object-formats in debug builds. Without this,
> ir_validate fails on that test.
>
> Shader-db results:
>
> GM45 (0x2A42):
> total instructions in shared programs: 3548093 -> 3545804 (-0.06%)
> instructions in affected programs: 213889 -> 211600 (-1.07%)
> helped: 543
> HURT: 2
>
> Iron Lake (0x0046):
> total instructions in shared programs: 4978454 -> 4975982 (-0.05%)
> instructions in affected programs: 226063 -> 223591 (-1.09%)
> helped: 597
> HURT: 5
>
> Sandy Bridge (0x0116):
> total instructions in shared programs: 6806814 -> 6803487 (-0.05%)
> instructions in affected programs: 447885 -> 444558 (-0.74%)
> helped: 1612
> HURT: 36
>
> Sandy Bridge (0x0116) NIR:
> total instructions in shared programs: 6813527 -> 6811992 (-0.02%)
> instructions in affected programs: 329020 -> 327485 (-0.47%)
> helped: 1002
> HURT: 196
>
> Ivy Bridge (0x0166):
> total instructions in shared programs: 6283080 -> 6279862 (-0.05%)
> instructions in affected programs: 421859 -> 418641 (-0.76%)
> helped: 1592
> HURT: 36
>
> Ivy Bridge (0x0166) NIR:
> total instructions in shared programs: 6319944 -> 6317148 (-0.04%)
> instructions in affected programs: 303221 -> 300425 (-0.92%)
> helped: 998
> HURT: 176
> GAINED: 4
>
> Haswell (0x0426):
> total instructions in shared programs: 5766971 -> 5764623 (-0.04%)
> instructions in affected programs: 382796 -> 380448 (-0.61%)
> helped: 1559
> HURT: 63
>
> Haswell (0x0426) NIR:
> total instructions in shared programs: 5793258 -> 5792647 (-0.01%)
> instructions in affected programs: 276929 -> 276318 (-0.22%)
> helped: 837
> HURT: 343
> GAINED: 4
>
> Broadwell (0x162E):
> total instructions in shared programs: 6813995 -> 6811377 (-0.04%)
> instructions in affected programs: 469734 -> 467116 (-0.56%)
> helped: 1772
> HURT: 78
> LOST: 1
>
> Broadwell (0x162E) NIR:
> total instructions in shared programs: 7009761 -> 7009142 (-0.01%)
> instructions in affected programs: 298433 -> 297814 (-0.21%)
> helped: 866
> HURT: 373
>
> Signed-off-by: Ian Romanick <ian.d.roman...@intel.com>
> ---
> src/glsl/opt_algebraic.cpp | 22 ++++++++++++++++++++++
> 1 file changed, 22 insertions(+)
>
> diff --git a/src/glsl/opt_algebraic.cpp b/src/glsl/opt_algebraic.cpp
> index 69c03ea..837b080 100644
> --- a/src/glsl/opt_algebraic.cpp
> +++ b/src/glsl/opt_algebraic.cpp
> @@ -560,6 +560,28 @@ ir_algebraic_visitor::handle_expression(ir_expression
> *ir)
> }
> }
> }
> +
> + /* If one of the multiplicands is an ir_unop_b2f, we can convert the
> + * multiply to a simple csel.
> + *
> + * x * b2f(condition) => mix( 0, x, condition)
> + */
> + for (unsigned i = 0; i < 2; i++) {
> + if (op_expr[i] == NULL)
> + continue;
> +
> + if (op_expr[i]->operation != ir_unop_b2f)
> + continue;
> +
> + /* swizzle_if_required is necessary on both operands. The b2f could
> + * be a scalar (common) with the other a vector, or the b2f could be
> + * a vector with the other a scalar (as in piglit's
> + * arb_texture_buffer_object-formats test).
> + */
> + return csel(swizzle_if_required(ir, op_expr[i]->operands[0]),
> + swizzle_if_required(ir, ir->operands[i ^ 1]),
> + ir_constant::zero(ir, ir->type));
> + }
> break;
>
> case ir_binop_div:
>
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