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i965/fs: Generate better code for ir_triop_csel. 

Previously, we generated an extra CMP instruction:

   cmp.ge.f0(8)   g4<1>D          g2<0,1,0>F      0F
   cmp.nz.f0(8)   null            g4<8,8,1>D      0D
   (+f0) sel(8)   g120<1>F        g2.4<0,1,0>F    g3<0,1,0>F

The first operand is always a boolean, and we want to predicate the SEL
on that.  Rather than producing a boolean value and comparing it against
zero, we can just produce a condition code in the flag register.

Now we generate:

   cmp.ge.f0(8)    null            g2<0,1,0>F      0F
   (+f0) sel(8)    g124<1>F        g2.4<0,1,0>F    g3<0,1,0>F

total instructions in shared programs: 5473459 -> 5473253 (-0.00%)
instructions in affected programs:     6219 -> 6013 (-3.31%)

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
This commit is contained in:
Kenneth Graunke 2014-10-15 18:57:07 -07:00
parent 32364a1fe5
commit 4d34c4b582
1 changed files with 13 additions and 5 deletions
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18
src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
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@ -487,6 +487,19 @@ fs_visitor::visit(ir_expression *ir)
return;
break;
case ir_triop_csel:
ir->operands[1]->accept(this);
op[1] = this->result;
ir->operands[2]->accept(this);
op[2] = this->result;
emit_bool_to_cond_code(ir->operands[0]);
this->result = fs_reg(this, ir->type);
inst = emit(SEL(this->result, op[1], op[2]));
inst->predicate = BRW_PREDICATE_NORMAL;
return;
case ir_unop_interpolate_at_centroid:
case ir_binop_interpolate_at_offset:
case ir_binop_interpolate_at_sample:
@ -1023,11 +1036,6 @@ fs_visitor::visit(ir_expression *ir)
break;
case ir_triop_csel:
emit(CMP(reg_null_d, op[0], fs_reg(0), BRW_CONDITIONAL_NZ));
inst = emit(BRW_OPCODE_SEL, this->result, op[1], op[2]);
inst->predicate = BRW_PREDICATE_NORMAL;
break;
case ir_unop_interpolate_at_centroid:
case ir_binop_interpolate_at_offset:
case ir_binop_interpolate_at_sample: