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On 07/21/2011 05:28 PM, Eric Anholt wrote:
> On Thu, 21 Jul 2011 12:16:58 -0700, "Ian Romanick" <i...@freedesktop.org>
> wrote:
>> From: Ian Romanick <ian.d.roman...@intel.com>
>>
>> Just like the non-constant array index lowering pass, compare all N
>> indices at once. For accesses to a vec4, this saves 3 comparison
>> instructions on a vector architecture.
>> ---
>> src/glsl/lower_vec_index_to_cond_assign.cpp | 57
>> ++++++++++++++++----------
>> 1 files changed, 35 insertions(+), 22 deletions(-)
>>
>> diff --git a/src/glsl/lower_vec_index_to_cond_assign.cpp
>> b/src/glsl/lower_vec_index_to_cond_assign.cpp
>> index 15992e2..26c5452 100644
>> --- a/src/glsl/lower_vec_index_to_cond_assign.cpp
>> +++ b/src/glsl/lower_vec_index_to_cond_assign.cpp
>> @@ -93,32 +93,40 @@
>> ir_vec_index_to_cond_assign_visitor::convert_vec_index_to_cond_assign(ir_rvalue
>> base_ir->insert_before(index);
>> deref = new(base_ir) ir_dereference_variable(index);
>> assign = new(base_ir) ir_assignment(deref, orig_deref->array_index,
>> NULL);
>> - base_ir->insert_before(assign);
>> + list.push_tail(assign);
>>
>> /* Temporary where we store whichever value we swizzle out. */
>> var = new(base_ir) ir_variable(ir->type, "vec_index_tmp_v",
>> ir_var_temporary);
>> - base_ir->insert_before(var);
>> + list.push_tail(var);
>> +
>> + /* Generate a single comparison condition "mask" for all of the
>> components
>> + * in the vector.
>> + */
>> + ir_rvalue *const cond_deref =
>> + compare_index_block(&list, index, 0,
>> + orig_deref->array->type->vector_elements,
>> + mem_ctx);
>>
>> /* Generate a conditional move of each vector element to the temp. */
>> for (i = 0; i < orig_deref->array->type->vector_elements; i++) {
>> - deref = new(base_ir) ir_dereference_variable(index);
>> - condition = new(base_ir) ir_expression(ir_binop_equal,
>> - glsl_type::bool_type,
>> - deref,
>> - new(base_ir) ir_constant(i));
>> + ir_rvalue *condition_swizzle =
>> + new(ir) ir_swizzle(cond_deref->clone(ir, NULL), i, 0, 0, 0, 1);
>
> If you've got the mem_ctx = ralloc_parent(base_ir) around already, it seems
> like the right thing to use here (and in a few other places in this code)
That was something odd about the original code. My addition of
'new(ir)' was a copy-and-paste mistake. I had intended it to be
'new(base_ir)' to follow the original code. But yeah. Either mem_ctx
should be removed, it should be used everywhere, or there should be a
comment explaining why the code is weird.
For the purpose of this commit, I'll just change the 'new(ir)' to
'new(base_ir)'.
> Other than that, switching the base_ir->insert_before(whatever) to
> list.push_tail() in various places (but not everywhere) seems strange.
The only instance of that is to put the whole set of new instructions in
the IR stream. I'll add a comment.
The reason it uses list.push_tail is because compare_index_block wants a
list as a parameter, so there's a list for at least some of the added
instructions.
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