1 files changed, 336 insertions, 0 deletions

diff --git a/src/compiler/glsl/opt_dead_code_local.cpp b/src/compiler/glsl/opt_dead_code_local.cpp
new file mode 100644
index 0000000000..d38fd2bf63
--- /dev/null
+++ b/src/compiler/glsl/opt_dead_code_local.cpp
@@ -0,0 +1,336 @@
+/*
+ * Copyright © 2010 Intel Corporation
+ *
+ * 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 opt_dead_code_local.cpp
+ *
+ * Eliminates local dead assignments from the code.
+ *
+ * This operates on basic blocks, tracking assignments and finding if
+ * they're used before the variable is completely reassigned.
+ *
+ * Compare this to ir_dead_code.cpp, which operates globally looking
+ * for assignments to variables that are never read.
+ */
+
+#include "ir.h"
+#include "ir_basic_block.h"
+#include "ir_optimization.h"
+#include "compiler/glsl_types.h"
+
+static bool debug = false;
+
+namespace {
+
+class assignment_entry : public exec_node
+{
+public:
+   assignment_entry(ir_variable *lhs, ir_assignment *ir)
+   {
+      assert(lhs);
+      assert(ir);
+      this->lhs = lhs;
+      this->ir = ir;
+      this->unused = ir->write_mask;
+   }
+
+   ir_variable *lhs;
+   ir_assignment *ir;
+
+   /* bitmask of xyzw channels written that haven't been used so far. */
+   int unused;
+};
+
+class kill_for_derefs_visitor : public ir_hierarchical_visitor {
+public:
+   kill_for_derefs_visitor(exec_list *assignments)
+   {
+      this->assignments = assignments;
+   }
+
+   void use_channels(ir_variable *const var, int used)
+   {
+      foreach_in_list_safe(assignment_entry, entry, this->assignments) {
+	 if (entry->lhs == var) {
+	    if (var->type->is_scalar() || var->type->is_vector()) {
+	       if (debug)
+		  printf("used %s (0x%01x - 0x%01x)\n", entry->lhs->name,
+			 entry->unused, used & 0xf);
+	       entry->unused &= ~used;
+	       if (!entry->unused)
+		  entry->remove();
+	    } else {
+	       if (debug)
+		  printf("used %s\n", entry->lhs->name);
+	       entry->remove();
+	    }
+	 }
+      }
+   }
+
+   virtual ir_visitor_status visit(ir_dereference_variable *ir)
+   {
+      use_channels(ir->var, ~0);
+
+      return visit_continue;
+   }
+
+   virtual ir_visitor_status visit(ir_swizzle *ir)
+   {
+      ir_dereference_variable *deref = ir->val->as_dereference_variable();
+      if (!deref)
+	 return visit_continue;
+
+      int used = 0;
+      used |= 1 << ir->mask.x;
+      used |= 1 << ir->mask.y;
+      used |= 1 << ir->mask.z;
+      used |= 1 << ir->mask.w;
+
+      use_channels(deref->var, used);
+
+      return visit_continue_with_parent;
+   }
+
+   virtual ir_visitor_status visit_leave(ir_emit_vertex *)
+   {
+      /* For the purpose of dead code elimination, emitting a vertex counts as
+       * "reading" all of the currently assigned output variables.
+       */
+      foreach_in_list_safe(assignment_entry, entry, this->assignments) {
+         if (entry->lhs->data.mode == ir_var_shader_out) {
+            if (debug)
+               printf("kill %s\n", entry->lhs->name);
+            entry->remove();
+         }
+      }
+
+      return visit_continue;
+   }
+
+private:
+   exec_list *assignments;
+};
+
+class array_index_visit : public ir_hierarchical_visitor {
+public:
+   array_index_visit(ir_hierarchical_visitor *v)
+   {
+      this->visitor = v;
+   }
+
+   virtual ir_visitor_status visit_enter(class ir_dereference_array *ir)
+   {
+      ir->array_index->accept(visitor);
+      return visit_continue;
+   }
+
+   static void run(ir_instruction *ir, ir_hierarchical_visitor *v)
+   {
+      array_index_visit top_visit(v);
+      ir->accept(& top_visit);
+   }
+
+   ir_hierarchical_visitor *visitor;
+};
+
+} /* unnamed namespace */
+
+/**
+ * Adds an entry to the available copy list if it's a plain assignment
+ * of a variable to a variable.
+ */
+static bool
+process_assignment(void *ctx, ir_assignment *ir, exec_list *assignments)
+{
+   ir_variable *var = NULL;
+   bool progress = false;
+   kill_for_derefs_visitor v(assignments);
+
+   /* Kill assignment entries for things used to produce this assignment. */
+   ir->rhs->accept(&v);
+   if (ir->condition) {
+      ir->condition->accept(&v);
+   }
+
+   /* Kill assignment enties used as array indices.
+    */
+   array_index_visit::run(ir->lhs, &v);
+   var = ir->lhs->variable_referenced();
+   assert(var);
+
+   /* Now, check if we did a whole-variable assignment. */
+   if (!ir->condition) {
+      ir_dereference_variable *deref_var = ir->lhs->as_dereference_variable();
+
+      /* If it's a vector type, we can do per-channel elimination of
+       * use of the RHS.
+       */
+      if (deref_var && (deref_var->var->type->is_scalar() ||
+			deref_var->var->type->is_vector())) {
+
+	 if (debug)
+	    printf("looking for %s.0x%01x to remove\n", var->name,
+		   ir->write_mask);
+
+	 foreach_in_list_safe(assignment_entry, entry, assignments) {
+	    if (entry->lhs != var)
+	       continue;
+
+            /* Skip if the assignment we're trying to eliminate isn't a plain
+             * variable deref. */
+            if (entry->ir->lhs->ir_type != ir_type_dereference_variable)
+               continue;
+
+	    int remove = entry->unused & ir->write_mask;
+	    if (debug) {
+	       printf("%s 0x%01x - 0x%01x = 0x%01x\n",
+		      var->name,
+		      entry->ir->write_mask,
+		      remove, entry->ir->write_mask & ~remove);
+	    }
+	    if (remove) {
+	       progress = true;
+
+	       if (debug) {
+		  printf("rewriting:\n  ");
+		  entry->ir->print();
+		  printf("\n");
+	       }
+
+	       entry->ir->write_mask &= ~remove;
+	       entry->unused &= ~remove;
+	       if (entry->ir->write_mask == 0) {
+		  /* Delete the dead assignment. */
+		  entry->ir->remove();
+		  entry->remove();
+	       } else {
+		  void *mem_ctx = ralloc_parent(entry->ir);
+		  /* Reswizzle the RHS arguments according to the new
+		   * write_mask.
+		   */
+		  unsigned components[4];
+		  unsigned channels = 0;
+		  unsigned next = 0;
+
+		  for (int i = 0; i < 4; i++) {
+		     if ((entry->ir->write_mask | remove) & (1 << i)) {
+			if (!(remove & (1 << i)))
+			   components[channels++] = next;
+			next++;
+		     }
+		  }
+
+		  entry->ir->rhs = new(mem_ctx) ir_swizzle(entry->ir->rhs,
+							   components,
+							   channels);
+		  if (debug) {
+		     printf("to:\n  ");
+		     entry->ir->print();
+		     printf("\n");
+		  }
+	       }
+	    }
+	 }
+      } else if (ir->whole_variable_written() != NULL) {
+	 /* We did a whole-variable assignment.  So, any instruction in
+	  * the assignment list with the same LHS is dead.
+	  */
+	 if (debug)
+	    printf("looking for %s to remove\n", var->name);
+	 foreach_in_list_safe(assignment_entry, entry, assignments) {
+	    if (entry->lhs == var) {
+	       if (debug)
+		  printf("removing %s\n", var->name);
+	       entry->ir->remove();
+	       entry->remove();
+	       progress = true;
+	    }
+	 }
+      }
+   }
+
+   /* Add this instruction to the assignment list available to be removed. */
+   assignment_entry *entry = new(ctx) assignment_entry(var, ir);
+   assignments->push_tail(entry);
+
+   if (debug) {
+      printf("add %s\n", var->name);
+
+      printf("current entries\n");
+      foreach_in_list(assignment_entry, entry, assignments) {
+	 printf("    %s (0x%01x)\n", entry->lhs->name, entry->unused);
+      }
+   }
+
+   return progress;
+}
+
+static void
+dead_code_local_basic_block(ir_instruction *first,
+			     ir_instruction *last,
+			     void *data)
+{
+   ir_instruction *ir, *ir_next;
+   /* List of avaialble_copy */
+   exec_list assignments;
+   bool *out_progress = (bool *)data;
+   bool progress = false;
+
+   void *ctx = ralloc_context(NULL);
+   /* Safe looping, since process_assignment */
+   for (ir = first, ir_next = (ir_instruction *)first->next;;
+	ir = ir_next, ir_next = (ir_instruction *)ir->next) {
+      ir_assignment *ir_assign = ir->as_assignment();
+
+      if (debug) {
+	 ir->print();
+	 printf("\n");
+      }
+
+      if (ir_assign) {
+	 progress = process_assignment(ctx, ir_assign, &assignments) || progress;
+      } else {
+	 kill_for_derefs_visitor kill(&assignments);
+	 ir->accept(&kill);
+      }
+
+      if (ir == last)
+	 break;
+   }
+   *out_progress = progress;
+   ralloc_free(ctx);
+}
+
+/**
+ * Does a copy propagation pass on the code present in the instruction stream.
+ */
+bool
+do_dead_code_local(exec_list *instructions)
+{
+   bool progress = false;
+
+   call_for_basic_blocks(instructions, dead_code_local_basic_block, &progress);
+
+   return progress;
+}