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i965: Implement b2f and b2i using negation.

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Booleans are represented as 0/-1 on modern hardware which means we can
just negate them to convert them into a numeric type.  Negation has
the benefit that it can be implemented using a source modifier which
can easily be propagated into some other instruction.  shader-db
results on HSW:

total instructions in shared programs: 6349082 -> 6346693 (-0.04%)
instructions in affected programs:     40948 -> 38559 (-5.83%)
helped:                                123
HURT:                                  1
GAINED:                                1
LOST:                                  0

Reviewed-by: Matt Turner <mattst88@gmail.com>
This commit is contained in:
Francisco Jerez 2015-07-10 19:18:39 +03:00
parent 8fba933ca2
commit 3ee2daf23d
2 changed files with 2 additions and 9 deletions
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4
src/mesa/drivers/dri/i965/brw_fs_nir.cpp
View file

@ -968,10 +968,8 @@ fs_visitor::nir_emit_alu(const fs_builder &bld, nir_alu_instr *instr)
break;
case nir_op_b2i:
bld.AND(result, op[0], fs_reg(1));
break;
case nir_op_b2f:
bld.AND(retype(result, BRW_REGISTER_TYPE_UD), op[0], fs_reg(0x3f800000u));
bld.MOV(result, negate(op[0]));
break;
case nir_op_f2b:

7
src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
View file

@ -1733,16 +1733,11 @@ vec4_visitor::visit(ir_expression *ir)
emit(MOV(result_dst, op[0]));
break;
case ir_unop_b2i:
emit(AND(result_dst, op[0], src_reg(1)));
break;
case ir_unop_b2f:
if (devinfo->gen <= 5) {
resolve_bool_comparison(ir->operands[0], &op[0]);
}
op[0].type = BRW_REGISTER_TYPE_D;
result_dst.type = BRW_REGISTER_TYPE_D;
emit(AND(result_dst, op[0], src_reg(0x3f800000u)));
result_dst.type = BRW_REGISTER_TYPE_F;
emit(MOV(result_dst, negate(op[0])));
break;
case ir_unop_f2b:
emit(CMP(result_dst, op[0], src_reg(0.0f), BRW_CONDITIONAL_NZ));