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glsl: Optimize mul(a, -1) into neg(a).

Browse source 
Two extra instructions in some heroesofnewerth shaders, but a win for
everything else.

total instructions in shared programs: 1531352 -> 1530815 (-0.04%)
instructions in affected programs:     121898 -> 121361 (-0.44%)

Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
This commit is contained in:
Matt Turner 2013-10-15 23:42:19 -07:00
parent 197f3a33fb
commit a360ca7476
1 changed files with 23 additions and 0 deletions
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23
src/glsl/opt_algebraic.cpp
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@ -84,6 +84,12 @@ is_vec_one(ir_constant *ir)
return (ir == NULL) ? false : ir->is_one();
}
static inline bool
is_vec_negative_one(ir_constant *ir)
{
return (ir == NULL) ? false : ir->is_negative_one();
}
static inline bool
is_vec_basis(ir_constant *ir)
{
@ -287,6 +293,23 @@ ir_algebraic_visitor::handle_expression(ir_expression *ir)
this->progress = true;
return ir_constant::zero(ir, ir->type);
}
if (is_vec_negative_one(op_const[0])) {
this->progress = true;
temp = new(mem_ctx) ir_expression(ir_unop_neg,
ir->operands[1]->type,
ir->operands[1],
NULL);
return swizzle_if_required(ir, temp);
}
if (is_vec_negative_one(op_const[1])) {
this->progress = true;
temp = new(mem_ctx) ir_expression(ir_unop_neg,
ir->operands[0]->type,
ir->operands[0],
NULL);
return swizzle_if_required(ir, temp);
}
/* Reassociate multiplication of constants so that we can do
* constant folding.