[Mesa-dev] [PATCH 13/13] glsl: Compare vector indices in blocks

[Ian Romanick]

From: Ian Romanick <ian.d.romanick at 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
@@ -71,8 +71,6 @@ ir_vec_index_to_cond_assign_visitor::convert_vec_index_to_cond_assign(ir_rvalue
    ir_assignment *assign;
    ir_variable *index, *var;
    ir_dereference *deref;
-   ir_expression *condition;
-   ir_swizzle *swizzle;
    int i;
 
    if (!orig_deref)
@@ -86,6 +84,8 @@ ir_vec_index_to_cond_assign_visitor::convert_vec_index_to_cond_assign(ir_rvalue
 
    assert(orig_deref->array_index->type->base_type == GLSL_TYPE_INT);
 
+   exec_list list;
+
    /* Store the index to a temporary to avoid reusing its tree. */
    index = new(base_ir) ir_variable(glsl_type::int_type,
 				    "vec_index_tmp_i",
@@ -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);
 
       /* Just clone the rest of the deref chain when trying to get at the
        * underlying variable.
        */
-      swizzle = new(base_ir) ir_swizzle(orig_deref->array->clone(mem_ctx, NULL),
-					i, 0, 0, 0, 1);
+      ir_rvalue *swizzle =
+	 new(base_ir) ir_swizzle(orig_deref->array->clone(mem_ctx, NULL),
+				 i, 0, 0, 0, 1);
 
       deref = new(base_ir) ir_dereference_variable(var);
-      assign = new(base_ir) ir_assignment(deref, swizzle, condition);
-      base_ir->insert_before(assign);
+      assign = new(base_ir) ir_assignment(deref, swizzle, condition_swizzle);
+      list.push_tail(assign);
    }
 
+   base_ir->insert_before(&list);
+
    this->progress = true;
    return new(base_ir) ir_dereference_variable(var);
 }
@@ -189,24 +197,29 @@ ir_vec_index_to_cond_assign_visitor::visit_leave(ir_assignment *ir)
    assign = new(ir) ir_assignment(deref, ir->rhs, NULL);
    list.push_tail(assign);
 
+   /* 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++) {
-      ir_rvalue *condition, *swizzle;
+      ir_rvalue *condition_swizzle =
+	 new(ir) ir_swizzle(cond_deref->clone(ir, NULL), i, 0, 0, 0, 1);
 
-      deref = new(ir) ir_dereference_variable(index);
-      condition = new(ir) ir_expression(ir_binop_equal,
-					glsl_type::bool_type,
-					deref,
-					new(ir) ir_constant(i));
 
       /* Just clone the rest of the deref chain when trying to get at the
        * underlying variable.
        */
-      swizzle = new(ir) ir_swizzle(orig_deref->array->clone(mem_ctx, NULL),
-				   i, 0, 0, 0, 1);
+      ir_rvalue *swizzle =
+	 new(ir) ir_swizzle(orig_deref->array->clone(mem_ctx, NULL),
+			    i, 0, 0, 0, 1);
 
       deref = new(ir) ir_dereference_variable(var);
-      assign = new(ir) ir_assignment(swizzle, deref, condition);
+      assign = new(ir) ir_assignment(swizzle, deref, condition_swizzle);
       list.push_tail(assign);
    }
 
-- 
1.7.4.4