glsl: add pass to lower variable array indexing to conditional assignments

Currenly GLSL happily generates indirect addressing of any kind of
arrays.

Unfortunately DirectX 9 GPUs are not guaranteed to support any of them in
general.

This pass fixes that by lowering such constructs to a binary search on the
values, followed at the end by vectorized generation of equality masks, and
4 conditional assignments for each mask generation.

Note that this requires the ir_binop_equal change so that we can emit SEQ
to generate the boolean masks.

Unfortunately, ir_structure_splitting is too dumb to turn the resulting
constant array references to individual variables, so this will need to
be added too before this pass can actually be effective for temps.

Several patches in the glsl2-lower-variable-indexing were squashed
into this commit.  These patches fix bugs in Luca's original
implementation, and the individual patches can be seen in that branch.
This was done to aid bisecting in the future.

Signed-off-by: Ian Romanick <[email protected]>

5 files changed, 317 insertions, 0 deletions

diff --git a/src/glsl/Makefile b/src/glsl/Makefile
index 1746e18ad69..47ac42667c7 100644
--- a/src/glsl/Makefile
+++ b/src/glsl/Makefile
@@ -76,6 +76,7 @@ CXX_SOURCES = \
 	loop_controls.cpp \
 	loop_unroll.cpp \
 	lower_noise.cpp \
+	lower_variable_index_to_cond_assign.cpp \
 	opt_redundant_jumps.cpp \
 	s_expression.cpp
 
diff --git a/src/glsl/Makefile.am b/src/glsl/Makefile.am
index f62a85e8930..5f013c31e9d 100644
--- a/src/glsl/Makefile.am
+++ b/src/glsl/Makefile.am
@@ -67,6 +67,7 @@ glsl_SOURCES = \
 	loop_controls.cpp \
 	loop_unroll.cpp \
 	lower_noise.cpp \
+	lower_variable_index_to_cond_assign.cpp \
 	opt_redundant_jumps.cpp
 
 BUILT_SOURCES = glsl_parser.h glsl_parser.cpp glsl_lexer.cpp
diff --git a/src/glsl/SConscript b/src/glsl/SConscript
index 6e2ef2d61f1..c183e208d63 100644
--- a/src/glsl/SConscript
+++ b/src/glsl/SConscript
@@ -73,6 +73,7 @@ sources = [
     'loop_controls.cpp',
     'loop_unroll.cpp',
     'lower_noise.cpp',
+    'lower_variable_index_to_cond_assign.cpp',
     'opt_redundant_jumps.cpp',
     's_expression.cpp',
 ]
diff --git a/src/glsl/ir_optimization.h b/src/glsl/ir_optimization.h
index b365ed2b235..5c8dc17d337 100644
--- a/src/glsl/ir_optimization.h
+++ b/src/glsl/ir_optimization.h
@@ -56,4 +56,5 @@ bool do_tree_grafting(exec_list *instructions);
 bool do_vec_index_to_cond_assign(exec_list *instructions);
 bool do_vec_index_to_swizzle(exec_list *instructions);
 bool lower_noise(exec_list *instructions);
+bool lower_variable_index_to_cond_assign(exec_list *instructions);
 bool optimize_redundant_jumps(exec_list *instructions);
diff --git a/src/glsl/lower_variable_index_to_cond_assign.cpp b/src/glsl/lower_variable_index_to_cond_assign.cpp
new file mode 100644
index 00000000000..d9e6379c390
--- /dev/null
+++ b/src/glsl/lower_variable_index_to_cond_assign.cpp
@@ -0,0 +1,313 @@
+/*
+ * Copyright © 2010 Luca Barbieri
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+/**
+ * \file lower_variable_index_to_cond_assign.cpp
+ *
+ * Turns non-constant indexing into array types to a series of
+ * conditional moves of each element into a temporary.
+ *
+ * Pre-DX10 GPUs often don't have a native way to do this operation,
+ * and this works around that.
+ */
+
+#include "ir.h"
+#include "ir_rvalue_visitor.h"
+#include "ir_optimization.h"
+#include "glsl_types.h"
+#include "main/macros.h"
+
+struct assignment_generator
+{
+   ir_instruction* base_ir;
+   ir_rvalue* array;
+   bool is_write;
+   ir_variable* var;
+
+   assignment_generator()
+   {
+   }
+
+   void generate(unsigned i, ir_rvalue* condition, exec_list *list) const
+   {
+      /* Just clone the rest of the deref chain when trying to get at the
+       * underlying variable.
+       */
+      void *mem_ctx = talloc_parent(base_ir);
+      ir_rvalue *element =
+	 new(mem_ctx) ir_dereference_array(this->array->clone(mem_ctx, NULL),
+					   new(mem_ctx) ir_constant(i));
+      ir_rvalue *variable = new(mem_ctx) ir_dereference_variable(this->var);
+
+      ir_assignment *assignment = (is_write)
+	 ? new(mem_ctx) ir_assignment(element, variable, condition)
+	 : new(mem_ctx) ir_assignment(variable, element, condition);
+
+      list->push_tail(assignment);
+   }
+};
+
+struct switch_generator
+{
+   /* make TFunction a template parameter if you need to use other generators */
+   typedef assignment_generator TFunction;
+   const TFunction& generator;
+
+   ir_variable* index;
+   unsigned linear_sequence_max_length;
+   unsigned condition_components;
+
+   void *mem_ctx;
+
+   switch_generator(const TFunction& generator, ir_variable *index,
+		    unsigned linear_sequence_max_length,
+		    unsigned condition_components)
+      : generator(generator), index(index),
+	linear_sequence_max_length(linear_sequence_max_length),
+	condition_components(condition_components)
+   {
+      this->mem_ctx = talloc_parent(index);
+   }
+
+   void linear_sequence(unsigned begin, unsigned end, exec_list *list)
+   {
+      if (begin == end)
+         return;
+
+      /* If the array access is a read, read the first element of this subregion
+       * unconditionally.  The remaining tests will possibly overwrite this
+       * value with one of the other array elements.
+       *
+       * This optimization cannot be done for writes because it will cause the
+       * first element of the subregion to be written possibly *in addition* to
+       * one of the other elements.
+       */
+      unsigned first;
+      if (!this->generator.is_write) {
+	 this->generator.generate(begin, 0, list);
+	 first = begin + 1;
+      } else {
+	 first = begin;
+      }
+
+      for (unsigned i = first; i < end; i += 4) {
+         const unsigned comps = MIN2(condition_components, end - i);
+
+         ir_rvalue *broadcast_index =
+	    new(this->mem_ctx) ir_dereference_variable(index);
+
+         if (comps) {
+	    const ir_swizzle_mask m = { 0, 1, 2, 3, comps, false };
+	    broadcast_index = new(this->mem_ctx) ir_swizzle(broadcast_index, m);
+	 }
+
+	 /* Compare the desired index value with the next block of four indices.
+	  */
+         ir_constant_data test_indices_data;
+         memset(&test_indices_data, 0, sizeof(test_indices_data));
+         test_indices_data.i[0] = i;
+         test_indices_data.i[1] = i + 1;
+         test_indices_data.i[2] = i + 2;
+         test_indices_data.i[3] = i + 3;
+         ir_constant *const test_indices =
+	    new(this->mem_ctx) ir_constant(broadcast_index->type,
+					   &test_indices_data);
+
+         ir_rvalue *const condition_val =
+	    new(this->mem_ctx) ir_expression(ir_binop_equal,
+					     &glsl_type::bool_type[comps - 1],
+					     broadcast_index,
+					     test_indices);
+
+         ir_variable *const condition =
+	    new(this->mem_ctx) ir_variable(condition_val->type,
+					   "dereference_array_condition",
+					   ir_var_temporary);
+         list->push_tail(condition);
+
+	 ir_rvalue *const cond_deref =
+	    new(this->mem_ctx) ir_dereference_variable(condition);
+         list->push_tail(new(this->mem_ctx) ir_assignment(cond_deref,
+							  condition_val, 0));
+
+         if (comps == 1) {
+	    ir_rvalue *const cond_deref =
+	       new(this->mem_ctx) ir_dereference_variable(condition);
+
+            this->generator.generate(i, cond_deref, list);
+         } else {
+            for (unsigned j = 0; j < comps; j++) {
+	       ir_rvalue *const cond_deref =
+		  new(this->mem_ctx) ir_dereference_variable(condition);
+	       ir_rvalue *const cond_swiz =
+		  new(this->mem_ctx) ir_swizzle(cond_deref, j, 0, 0, 0, 1);
+
+               this->generator.generate(i + j, cond_swiz, list);
+            }
+         }
+      }
+   }
+
+   void bisect(unsigned begin, unsigned end, exec_list *list)
+   {
+      unsigned middle = (begin + end) >> 1;
+
+      assert(index->type->is_integer());
+
+      ir_constant *const middle_c = (index->type->base_type == GLSL_TYPE_UINT)
+	 ? new(this->mem_ctx) ir_constant((unsigned)middle)
+         : new(this->mem_ctx) ir_constant((int)middle);
+
+
+      ir_dereference_variable *deref =
+	 new(this->mem_ctx) ir_dereference_variable(this->index);
+
+      ir_expression *less =
+	 new(this->mem_ctx) ir_expression(ir_binop_less, glsl_type::bool_type,
+					  deref, middle_c);
+
+      ir_if *if_less = new(this->mem_ctx) ir_if(less);
+
+      generate(begin, middle, &if_less->then_instructions);
+      generate(middle, end, &if_less->else_instructions);
+
+      list->push_tail(if_less);
+   }
+
+   void generate(unsigned begin, unsigned end, exec_list *list)
+   {
+      unsigned length = end - begin;
+      if (length <= this->linear_sequence_max_length)
+         return linear_sequence(begin, end, list);
+      else
+         return bisect(begin, end, list);
+   }
+};
+
+/**
+ * Visitor class for replacing expressions with ir_constant values.
+ */
+
+class variable_index_to_cond_assign_visitor : public ir_rvalue_visitor {
+public:
+   variable_index_to_cond_assign_visitor()
+   {
+      this->progress = false;
+   }
+
+   bool progress;
+
+   ir_variable *convert_dereference_array(ir_dereference_array *orig_deref,
+					  ir_rvalue* value)
+   {
+      unsigned length;
+      if (orig_deref->array->type->is_array())
+         length = orig_deref->array->type->length;
+      else if (orig_deref->array->type->is_matrix())
+         length = orig_deref->array->type->matrix_columns;
+      else
+         assert(0);
+
+      void *const mem_ctx = talloc_parent(base_ir);
+      ir_variable *var =
+	 new(mem_ctx) ir_variable(orig_deref->type, "dereference_array_value",
+				  ir_var_temporary);
+      base_ir->insert_before(var);
+
+      if (value) {
+	 ir_dereference *lhs = new(mem_ctx) ir_dereference_variable(var);
+	 ir_assignment *assign = new(mem_ctx) ir_assignment(lhs, value, NULL);
+
+         base_ir->insert_before(assign);
+      }
+
+      /* Store the index to a temporary to avoid reusing its tree. */
+      ir_variable *index =
+	 new(mem_ctx) ir_variable(orig_deref->array_index->type,
+				  "dereference_array_index", ir_var_temporary);
+      base_ir->insert_before(index);
+
+      ir_dereference *lhs = new(mem_ctx) ir_dereference_variable(index);
+      ir_assignment *assign =
+	 new(mem_ctx) ir_assignment(lhs, orig_deref->array_index, NULL);
+      base_ir->insert_before(assign);
+
+      assignment_generator ag;
+      ag.array = orig_deref->array;
+      ag.base_ir = base_ir;
+      ag.var = var;
+      ag.is_write = !!value;
+
+      switch_generator sg(ag, index, 4, 4);
+
+      exec_list list;
+      sg.generate(0, length, &list);
+      base_ir->insert_before(&list);
+
+      return var;
+   }
+
+   virtual void handle_rvalue(ir_rvalue **pir)
+   {
+      if (!*pir)
+         return;
+
+      ir_dereference_array* orig_deref = (*pir)->as_dereference_array();
+      if (orig_deref && !orig_deref->array_index->as_constant()
+            && (orig_deref->array->type->is_array()
+		|| orig_deref->array->type->is_matrix())) {
+         ir_variable* var = convert_dereference_array(orig_deref, 0);
+         assert(var);
+         *pir = new(talloc_parent(base_ir)) ir_dereference_variable(var);
+         this->progress = true;
+      }
+   }
+
+   ir_visitor_status
+   visit_leave(ir_assignment *ir)
+   {
+      ir_rvalue_visitor::visit_leave(ir);
+
+      ir_dereference_array *orig_deref = ir->lhs->as_dereference_array();
+
+      if (orig_deref && !orig_deref->array_index->as_constant()
+            && (orig_deref->array->type->is_array()
+		|| orig_deref->array->type->is_matrix())) {
+         convert_dereference_array(orig_deref, ir->rhs);
+         ir->remove();
+         this->progress = true;
+      }
+
+      return visit_continue;
+   }
+};
+
+bool
+lower_variable_index_to_cond_assign(exec_list *instructions)
+{
+   variable_index_to_cond_assign_visitor v;
+
+   visit_list_elements(&v, instructions);
+
+   return v.progress;
+}