glsl: Add a new opt_copy_propagation variant that does it channel-wise.

This patch cleans up many of the extra copies in GLSL IR introduced by
i965's scalarizing passes.  It doesn't result in a statistically
significant performance difference on nexuiz high settings (n=3) or my
demo (n=10), due to brw_fs.cpp's register coalescing covering most of
those extra moves anyway.  However, it does make the debug of wine's
GLSL shaders much more tractable, and reduces instruction count of
glsl-fs-convolution-2 from 376 to 288.

1 files changed, 461 insertions, 0 deletions

diff --git a/src/glsl/opt_copy_propagation_elements.cpp b/src/glsl/opt_copy_propagation_elements.cpp
new file mode 100644
index 00000000000..238a1a75eea
--- /dev/null
+++ b/src/glsl/opt_copy_propagation_elements.cpp
@@ -0,0 +1,461 @@
+/*
+ * 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_copy_propagation_elements.cpp
+ *
+ * Replaces usage of recently-copied components of variables with the
+ * previous copy of the variable.
+ *
+ * This pass can be compared with opt_copy_propagation, which operands
+ * on arbitrary whole-variable copies.  However, in order to handle
+ * the copy propagation of swizzled variables or writemasked writes,
+ * we want to track things on a channel-wise basis.  I found that
+ * trying to mix the swizzled/writemasked support here with the
+ * whole-variable stuff in opt_copy_propagation.cpp just made a mess,
+ * so this is separate despite the ACP handling being somewhat
+ * similar.
+ *
+ * This should reduce the number of MOV instructions in the generated
+ * programs unless copy propagation is also done on the LIR, and may
+ * help anyway by triggering other optimizations that live in the HIR.
+ */
+
+#include "ir.h"
+#include "ir_rvalue_visitor.h"
+#include "ir_basic_block.h"
+#include "ir_optimization.h"
+#include "glsl_types.h"
+
+static bool debug = false;
+
+class acp_entry : public exec_node
+{
+public:
+   acp_entry(ir_variable *lhs, ir_variable *rhs, int write_mask, int swizzle[4])
+   {
+      this->lhs = lhs;
+      this->rhs = rhs;
+      this->write_mask = write_mask;
+      memcpy(this->swizzle, swizzle, sizeof(this->swizzle));
+   }
+
+   acp_entry(acp_entry *a)
+   {
+      this->lhs = a->lhs;
+      this->rhs = a->rhs;
+      this->write_mask = a->write_mask;
+      memcpy(this->swizzle, a->swizzle, sizeof(this->swizzle));
+   }
+
+   ir_variable *lhs;
+   ir_variable *rhs;
+   unsigned int write_mask;
+   int swizzle[4];
+};
+
+
+class kill_entry : public exec_node
+{
+public:
+   kill_entry(ir_variable *var, int write_mask)
+   {
+      this->var = var;
+      this->write_mask = write_mask;
+   }
+
+   ir_variable *var;
+   unsigned int write_mask;
+};
+
+class ir_copy_propagation_elements_visitor : public ir_rvalue_visitor {
+public:
+   ir_copy_propagation_elements_visitor()
+   {
+      this->progress = false;
+      this->mem_ctx = ralloc_context(NULL);
+      this->shader_mem_ctx = NULL;
+      this->acp = new(mem_ctx) exec_list;
+      this->kills = new(mem_ctx) exec_list;
+   }
+   ~ir_copy_propagation_elements_visitor()
+   {
+      ralloc_free(mem_ctx);
+   }
+
+   virtual ir_visitor_status visit_enter(class ir_loop *);
+   virtual ir_visitor_status visit_enter(class ir_function_signature *);
+   virtual ir_visitor_status visit_leave(class ir_assignment *);
+   virtual ir_visitor_status visit_enter(class ir_call *);
+   virtual ir_visitor_status visit_enter(class ir_if *);
+
+   void handle_rvalue(ir_rvalue **rvalue);
+
+   void add_copy(ir_assignment *ir);
+   void kill(kill_entry *k);
+   void handle_if_block(exec_list *instructions);
+
+   /** List of acp_entry: The available copies to propagate */
+   exec_list *acp;
+   /**
+    * List of kill_entry: The variables whose values were killed in this
+    * block.
+    */
+   exec_list *kills;
+
+   bool progress;
+
+   bool killed_all;
+
+   /* Context for our local data structures. */
+   void *mem_ctx;
+   /* Context for allocating new shader nodes. */
+   void *shader_mem_ctx;
+};
+
+ir_visitor_status
+ir_copy_propagation_elements_visitor::visit_enter(ir_function_signature *ir)
+{
+   /* Treat entry into a function signature as a completely separate
+    * block.  Any instructions at global scope will be shuffled into
+    * main() at link time, so they're irrelevant to us.
+    */
+   exec_list *orig_acp = this->acp;
+   exec_list *orig_kills = this->kills;
+   bool orig_killed_all = this->killed_all;
+
+   this->acp = new(mem_ctx) exec_list;
+   this->kills = new(mem_ctx) exec_list;
+   this->killed_all = false;
+
+   visit_list_elements(this, &ir->body);
+
+   this->kills = orig_kills;
+   this->acp = orig_acp;
+   this->killed_all = orig_killed_all;
+
+   return visit_continue_with_parent;
+}
+
+ir_visitor_status
+ir_copy_propagation_elements_visitor::visit_leave(ir_assignment *ir)
+{
+   ir_dereference_variable *lhs = ir->lhs->as_dereference_variable();
+
+   if (lhs && (lhs->type->is_scalar() || lhs->type->is_vector())) {
+      kill_entry *k = new(mem_ctx) kill_entry(lhs->var, ir->write_mask);
+      kill(k);
+   }
+
+   add_copy(ir);
+
+   return visit_continue;
+}
+
+/**
+ * Replaces dereferences of ACP RHS variables with ACP LHS variables.
+ *
+ * This is where the actual copy propagation occurs.  Note that the
+ * rewriting of ir_dereference means that the ir_dereference instance
+ * must not be shared by multiple IR operations!
+ */
+void
+ir_copy_propagation_elements_visitor::handle_rvalue(ir_rvalue **ir)
+{
+   int swizzle_chan[4];
+   ir_dereference_variable *deref_var;
+   ir_variable *source[4] = {NULL, NULL, NULL, NULL};
+   int source_chan[4];
+   int chans;
+
+   if (!*ir)
+      return;
+
+   ir_swizzle *swizzle = (*ir)->as_swizzle();
+   if (swizzle) {
+      deref_var = swizzle->val->as_dereference_variable();
+      if (!deref_var)
+	 return;
+
+      swizzle_chan[0] = swizzle->mask.x;
+      swizzle_chan[1] = swizzle->mask.y;
+      swizzle_chan[2] = swizzle->mask.z;
+      swizzle_chan[3] = swizzle->mask.w;
+      chans = swizzle->type->vector_elements;
+   } else {
+      deref_var = (*ir)->as_dereference_variable();
+      if (!deref_var)
+	 return;
+
+      swizzle_chan[0] = 0;
+      swizzle_chan[1] = 1;
+      swizzle_chan[2] = 2;
+      swizzle_chan[3] = 3;
+      chans = deref_var->type->vector_elements;
+   }
+
+   if (this->in_assignee)
+      return;
+
+   ir_variable *var = deref_var->var;
+
+   /* Try to find ACP entries covering swizzle_chan[], hoping they're
+    * the same source variable.
+    */
+   foreach_iter(exec_list_iterator, iter, *this->acp) {
+      acp_entry *entry = (acp_entry *)iter.get();
+
+      if (var == entry->lhs) {
+	 for (int c = 0; c < chans; c++) {
+	    if (entry->write_mask & (1 << swizzle_chan[c])) {
+	       source[c] = entry->rhs;
+	       source_chan[c] = entry->swizzle[swizzle_chan[c]];
+	    }
+	 }
+      }
+   }
+
+   /* Make sure all channels are copying from the same source variable. */
+   if (!source[0])
+      return;
+   for (int c = 1; c < chans; c++) {
+      if (source[c] != source[0])
+	 return;
+   }
+
+   if (!shader_mem_ctx)
+      shader_mem_ctx = ralloc_parent(deref_var);
+
+   if (debug) {
+      printf("Copy propagation from:\n");
+      (*ir)->print();
+   }
+
+   deref_var = new(shader_mem_ctx) ir_dereference_variable(source[0]);
+   *ir = new(shader_mem_ctx) ir_swizzle(deref_var,
+					source_chan[0],
+					source_chan[1],
+					source_chan[2],
+					source_chan[3],
+					chans);
+
+   if (debug) {
+      printf("to:\n");
+      (*ir)->print();
+      printf("\n");
+   }
+}
+
+
+ir_visitor_status
+ir_copy_propagation_elements_visitor::visit_enter(ir_call *ir)
+{
+   /* Do copy propagation on call parameters, but skip any out params */
+   exec_list_iterator sig_param_iter = ir->get_callee()->parameters.iterator();
+   foreach_iter(exec_list_iterator, iter, ir->actual_parameters) {
+      ir_variable *sig_param = (ir_variable *)sig_param_iter.get();
+      ir_instruction *ir = (ir_instruction *)iter.get();
+      if (sig_param->mode != ir_var_out && sig_param->mode != ir_var_inout) {
+         ir->accept(this);
+      }
+      sig_param_iter.next();
+   }
+
+   /* Since we're unlinked, we don't (necessarily) know the side effects of
+    * this call.  So kill all copies.
+    */
+   acp->make_empty();
+   this->killed_all = true;
+
+   return visit_continue_with_parent;
+}
+
+void
+ir_copy_propagation_elements_visitor::handle_if_block(exec_list *instructions)
+{
+   exec_list *orig_acp = this->acp;
+   exec_list *orig_kills = this->kills;
+   bool orig_killed_all = this->killed_all;
+
+   this->acp = new(mem_ctx) exec_list;
+   this->kills = new(mem_ctx) exec_list;
+   this->killed_all = false;
+
+   /* Populate the initial acp with a copy of the original */
+   foreach_iter(exec_list_iterator, iter, *orig_acp) {
+      acp_entry *a = (acp_entry *)iter.get();
+      this->acp->push_tail(new(this->mem_ctx) acp_entry(a));
+   }
+
+   visit_list_elements(this, instructions);
+
+   if (this->killed_all) {
+      orig_acp->make_empty();
+   }
+
+   exec_list *new_kills = this->kills;
+   this->kills = orig_kills;
+   this->acp = orig_acp;
+   this->killed_all = this->killed_all || orig_killed_all;
+
+   /* Move the new kills into the parent block's list, removing them
+    * from the parent's ACP list in the process.
+    */
+   foreach_list_safe(node, new_kills) {
+      kill_entry *k = (kill_entry *)node;
+      kill(k);
+   }
+}
+
+ir_visitor_status
+ir_copy_propagation_elements_visitor::visit_enter(ir_if *ir)
+{
+   ir->condition->accept(this);
+
+   handle_if_block(&ir->then_instructions);
+   handle_if_block(&ir->else_instructions);
+
+   /* handle_if_block() already descended into the children. */
+   return visit_continue_with_parent;
+}
+
+ir_visitor_status
+ir_copy_propagation_elements_visitor::visit_enter(ir_loop *ir)
+{
+   exec_list *orig_acp = this->acp;
+   exec_list *orig_kills = this->kills;
+   bool orig_killed_all = this->killed_all;
+
+   /* FINISHME: For now, the initial acp for loops is totally empty.
+    * We could go through once, then go through again with the acp
+    * cloned minus the killed entries after the first run through.
+    */
+   this->acp = new(mem_ctx) exec_list;
+   this->kills = new(mem_ctx) exec_list;
+   this->killed_all = false;
+
+   visit_list_elements(this, &ir->body_instructions);
+
+   if (this->killed_all) {
+      orig_acp->make_empty();
+   }
+
+   exec_list *new_kills = this->kills;
+   this->kills = orig_kills;
+   this->acp = orig_acp;
+   this->killed_all = this->killed_all || orig_killed_all;
+
+   foreach_list_safe(node, new_kills) {
+      kill_entry *k = (kill_entry *)node;
+      kill(k);
+   }
+
+   /* already descended into the children. */
+   return visit_continue_with_parent;
+}
+
+/* Remove any entries currently in the ACP for this kill. */
+void
+ir_copy_propagation_elements_visitor::kill(kill_entry *k)
+{
+   foreach_list_safe(node, acp) {
+      acp_entry *entry = (acp_entry *)node;
+
+      if (entry->lhs == k->var) {
+	 entry->write_mask = entry->write_mask & ~k->write_mask;
+	 if (entry->write_mask == 0)
+	    entry->remove();
+      }
+      if (entry->rhs == k->var) {
+	 entry->remove();
+      }
+   }
+
+   /* If we were on a list, remove ourselves before inserting */
+   if (k->next)
+      k->remove();
+
+   this->kills->push_tail(k);
+}
+
+/**
+ * Adds directly-copied channels between vector variables to the available
+ * copy propagation list.
+ */
+void
+ir_copy_propagation_elements_visitor::add_copy(ir_assignment *ir)
+{
+   acp_entry *entry;
+   int orig_swizzle[4] = {0, 1, 2, 3};
+   int swizzle[4];
+
+   if (ir->condition) {
+      ir_constant *condition = ir->condition->as_constant();
+      if (!condition || !condition->value.b[0])
+	 return;
+   }
+
+   ir_dereference_variable *lhs = ir->lhs->as_dereference_variable();
+   if (!lhs || !(lhs->type->is_scalar() || lhs->type->is_vector()))
+      return;
+
+   ir_dereference_variable *rhs = ir->rhs->as_dereference_variable();
+   if (!rhs) {
+      ir_swizzle *swiz = ir->rhs->as_swizzle();
+      if (!swiz)
+	 return;
+
+      rhs = swiz->val->as_dereference_variable();
+      if (!rhs)
+	 return;
+
+      orig_swizzle[0] = swiz->mask.x;
+      orig_swizzle[1] = swiz->mask.y;
+      orig_swizzle[2] = swiz->mask.z;
+      orig_swizzle[3] = swiz->mask.w;
+   }
+
+   /* Move the swizzle channels out to the positions they match in the
+    * destination.  We don't want to have to rewrite the swizzle[]
+    * array every time we clear a bit of the write_mask.
+    */
+   int j = 0;
+   for (int i = 0; i < 4; i++) {
+      if (ir->write_mask & (1 << i))
+	 swizzle[i] = orig_swizzle[j++];
+   }
+
+   entry = new(this->mem_ctx) acp_entry(lhs->var, rhs->var, ir->write_mask,
+					swizzle);
+   this->acp->push_tail(entry);
+}
+
+bool
+do_copy_propagation_elements(exec_list *instructions)
+{
+   ir_copy_propagation_elements_visitor v;
+
+   visit_list_elements(&v, instructions);
+
+   return v.progress;
+}