ra: First cut at a graph-coloring register allocator for mesa.

Notably missing is choice of registers to spill.

3 files changed, 431 insertions, 0 deletions

diff --git a/src/mesa/program/register_allocate.c b/src/mesa/program/register_allocate.c
new file mode 100644
index 0000000000..03f04697bf
--- /dev/null
+++ b/src/mesa/program/register_allocate.c
@@ -0,0 +1,361 @@
+/*
+ * 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.
+ *
+ * Authors:
+ *    Eric Anholt <eric@anholt.net>
+ *
+ */
+
+/** @file register_allocate.c
+ *
+ * Graph-coloring register allocator.
+ */
+
+#include <talloc.h>
+
+#include "main/imports.h"
+#include "main/macros.h"
+#include "main/mtypes.h"
+#include "register_allocate.h"
+
+struct ra_reg {
+   char *name;
+   GLboolean *conflicts;
+};
+
+struct ra_regs {
+   struct ra_reg *regs;
+   unsigned int count;
+
+   struct ra_class **classes;
+   unsigned int class_count;
+};
+
+struct ra_class {
+   GLboolean *regs;
+
+   /**
+    * p_B in Runeson/Nyström paper.
+    *
+    * This is "how many regs are in the set."
+    */
+   unsigned int p;
+
+   /**
+    * q_B,C in Runeson/Nyström paper.
+    */
+   unsigned int *q;
+};
+
+struct ra_node {
+   GLboolean *adjacency;
+   unsigned int class;
+   unsigned int adjacency_count;
+   unsigned int reg;
+   GLboolean in_stack;
+};
+
+struct ra_graph {
+   struct ra_regs *regs;
+   /**
+    * the variables that need register allocation.
+    */
+   struct ra_node *nodes;
+   unsigned int count; /**< count of nodes. */
+
+   unsigned int *stack;
+   unsigned int stack_count;
+};
+
+struct ra_regs *
+ra_alloc_reg_set(unsigned int count)
+{
+   unsigned int i;
+   struct ra_regs *regs;
+
+   regs = talloc_zero(NULL, struct ra_regs);
+   regs->count = count;
+   regs->regs = talloc_zero_array(regs, struct ra_reg, count);
+
+   for (i = 0; i < count; i++) {
+      regs->regs[i].conflicts = talloc_zero_array(regs->regs, GLboolean, count);
+      regs->regs[i].conflicts[i] = GL_TRUE;
+   }
+
+   return regs;
+}
+
+void
+ra_add_reg_conflict(struct ra_regs *regs, unsigned int r1, unsigned int r2)
+{
+   regs->regs[r1].conflicts[r2] = GL_TRUE;
+   regs->regs[r2].conflicts[r1] = GL_TRUE;
+}
+
+unsigned int
+ra_alloc_reg_class(struct ra_regs *regs)
+{
+   struct ra_class *class;
+
+   regs->classes = talloc_realloc(regs, regs->classes,
+				  struct ra_class *,
+				  regs->class_count + 1);
+
+   class = talloc_zero(regs, struct ra_class);
+   regs->classes[regs->class_count] = class;
+
+   class->regs = talloc_zero_array(class, GLboolean, regs->count);
+
+   return regs->class_count++;
+}
+
+void
+ra_class_add_reg(struct ra_regs *regs, unsigned int c, unsigned int r)
+{
+   struct ra_class *class = regs->classes[c];
+
+   class->regs[r] = GL_TRUE;
+   class->p++;
+}
+
+/**
+ * Must be called after all conflicts and register classes have been
+ * set up and before the register set is used for allocation.
+ */
+void
+ra_set_finalize(struct ra_regs *regs)
+{
+   unsigned int b, c;
+
+   for (b = 0; b < regs->class_count; b++) {
+      regs->classes[b]->q = talloc_array(regs, unsigned int, regs->class_count);
+   }
+
+   /* Compute, for each class B and C, how many regs of B an
+    * allocation to C could conflict with.
+    */
+   for (b = 0; b < regs->class_count; b++) {
+      for (c = 0; c < regs->class_count; c++) {
+	 unsigned int rc;
+	 int max_conflicts = 0;
+
+	 for (rc = 0; rc < regs->count; rc++) {
+	    unsigned int rb;
+	    int conflicts = 0;
+
+	    if (!regs->classes[c]->regs[rc])
+	       continue;
+
+	    for (rb = 0; rb < regs->count; rb++) {
+	       if (regs->classes[b]->regs[rb] &&
+		   regs->regs[rb].conflicts[rc])
+		  conflicts++;
+	    }
+	    max_conflicts = MAX2(max_conflicts, conflicts);
+	 }
+	 regs->classes[b]->q[c] = max_conflicts;
+      }
+   }
+}
+
+struct ra_graph *
+ra_alloc_interference_graph(struct ra_regs *regs, unsigned int count)
+{
+   struct ra_graph *g;
+   unsigned int i;
+
+   g = talloc_zero(regs, struct ra_graph);
+   g->regs = regs;
+   g->nodes = talloc_zero_array(g, struct ra_node, count);
+   g->count = count;
+
+   g->stack = talloc_zero_array(g, unsigned int, count);
+
+   for (i = 0; i < count; i++) {
+      g->nodes[i].adjacency = talloc_zero_array(g, GLboolean, count);
+      g->nodes[i].adjacency[i] = GL_TRUE;
+      g->nodes[i].reg = ~0;
+   }
+
+   return g;
+}
+
+void
+ra_set_node_class(struct ra_graph *g,
+		  unsigned int n, unsigned int class)
+{
+   g->nodes[n].class = class;
+}
+
+void
+ra_add_node_interference(struct ra_graph *g,
+			 unsigned int n1, unsigned int n2)
+{
+   if (g->nodes[n1].adjacency[n2])
+      return;
+
+   g->nodes[n1].adjacency[n2] = GL_TRUE;
+   g->nodes[n2].adjacency_count++;
+   g->nodes[n2].adjacency[n1] = GL_TRUE;
+   g->nodes[n2].adjacency_count++;
+}
+
+static GLboolean pq_test(struct ra_graph *g, unsigned int n)
+{
+   unsigned int j;
+   unsigned int q = 0;
+   int n_class = g->nodes[n].class;
+
+   for (j = 0; j < g->count; j++) {
+      if (j == n || g->nodes[j].in_stack)
+	 continue;
+
+      if (g->nodes[n].adjacency[j]) {
+	 unsigned int j_class = g->nodes[j].class;
+	 q += g->regs->classes[n_class]->q[j_class];
+      }
+   }
+
+   return q < g->regs->classes[n_class]->p;
+}
+
+/**
+ * Simplifies the interference graph by pushing all
+ * trivially-colorable nodes into a stack of nodes to be colored,
+ * removing them from the graph, and rinsing and repeating.
+ *
+ * Returns GL_TRUE if all nodes were removed from the graph.  GL_FALSE
+ * means that either spilling will be required, or optimistic coloring
+ * should be applied.
+ */
+GLboolean
+ra_simplify(struct ra_graph *g)
+{
+   GLboolean progress = GL_TRUE;
+   int i;
+
+   while (progress) {
+      progress = GL_FALSE;
+
+      for (i = g->count - 1; i >= 0; i--) {
+	 if (g->nodes[i].in_stack)
+	    continue;
+
+	 if (pq_test(g, i)) {
+	    g->stack[g->stack_count] = i;
+	    g->stack_count++;
+	    g->nodes[i].in_stack = GL_TRUE;
+	    progress = GL_TRUE;
+	 }
+      }
+   }
+
+   for (i = 0; i < g->count; i++) {
+      if (!g->nodes[i].in_stack)
+	 return GL_FALSE;
+   }
+
+   return GL_TRUE;
+}
+
+/**
+ * Pops nodes from the stack back into the graph, coloring them with
+ * registers as they go.
+ *
+ * If all nodes were trivially colorable, then this must succeed.  If
+ * not (optimistic coloring), then it may return GL_FALSE;
+ */
+GLboolean
+ra_select(struct ra_graph *g)
+{
+   int i;
+
+   while (g->stack_count != 0) {
+      unsigned int r;
+      int n = g->stack[g->stack_count - 1];
+      struct ra_class *c = g->regs->classes[g->nodes[n].class];
+
+      /* Find the lowest-numbered reg which is not used by a member
+       * of the graph adjacent to us.
+       */
+      for (r = 0; r < g->regs->count; r++) {
+	 if (!c->regs[r])
+	    continue;
+
+	 /* Check if any of our neighbors conflict with this register choice. */
+	 for (i = 0; i < g->count; i++) {
+	    if (g->nodes[n].adjacency[i] &&
+	       !g->nodes[i].in_stack &&
+		g->regs->regs[r].conflicts[g->nodes[i].reg]) {
+	       break;
+	    }
+	 }
+	 if (i == g->count)
+	    break;
+      }
+      if (r == g->regs->count)
+	 return GL_FALSE;
+
+      g->nodes[n].reg = r;
+      g->nodes[n].in_stack = GL_FALSE;
+      g->stack_count--;
+   }
+
+   return GL_TRUE;
+}
+
+/**
+ * Optimistic register coloring: Just push the remaining nodes
+ * on the stack.  They'll be colored first in ra_select(), and
+ * if they succeed then the locally-colorable nodes are still
+ * locally-colorable and the rest of the register allocation
+ * will succeed.
+ */
+void
+ra_optimistic_color(struct ra_graph *g)
+{
+   unsigned int i;
+
+   for (i = 0; i < g->count; i++) {
+      if (g->nodes[i].in_stack)
+	 continue;
+
+      g->stack[g->stack_count] = i;
+      g->stack_count++;
+      g->nodes[i].in_stack = GL_TRUE;
+   }
+}
+
+GLboolean
+ra_allocate_no_spills(struct ra_graph *g)
+{
+   if (!ra_simplify(g)) {
+      ra_optimistic_color(g);
+   }
+   return ra_select(g);
+}
+
+unsigned int
+ra_get_node_reg(struct ra_graph *g, unsigned int n)
+{
+   return g->nodes[n].reg;
+}
diff --git a/src/mesa/program/register_allocate.h b/src/mesa/program/register_allocate.h
new file mode 100644
index 0000000000..42647b50b8
--- /dev/null
+++ b/src/mesa/program/register_allocate.h
@@ -0,0 +1,69 @@
+/*
+ * 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.
+ *
+ * Authors:
+ *    Eric Anholt <eric@anholt.net>
+ *
+ */
+
+struct ra_class;
+struct ra_regs;
+
+/* @{
+ * Register set setup.
+ *
+ * This should be done once at backend initializaion, as
+ * ra_set_finalize is O(r^2*c^2).  The registers may be virtual
+ * registers, such as aligned register pairs that conflict with the
+ * two real registers from which they are composed.
+ */
+struct ra_regs *ra_alloc_reg_set(unsigned int count);
+unsigned int ra_alloc_reg_class(struct ra_regs *regs);
+void ra_add_reg_conflict(struct ra_regs *regs,
+			 unsigned int r1, unsigned int r2);
+void ra_class_add_reg(struct ra_regs *regs, unsigned int c, unsigned int reg);
+void ra_set_finalize(struct ra_regs *regs);
+/** @} */
+
+/** @{ Interference graph setup.
+ *
+ * Each interference graph node is a virtual variable in the IL.  It
+ * is up to the user to ra_set_node_class() for the virtual variable,
+ * and compute live ranges and ra_node_interfere() between conflicting
+ * live ranges.
+ */
+struct ra_graph *ra_alloc_interference_graph(struct ra_regs *regs,
+					     unsigned int count);
+void ra_set_node_class(struct ra_graph *g, unsigned int n, unsigned int c);
+void ra_add_node_interference(struct ra_graph *g,
+			      unsigned int n1, unsigned int n2);
+/** @} */
+
+/** @{ Graph-coloring register allocation */
+GLboolean ra_simplify(struct ra_graph *g);
+void ra_optimistic_color(struct ra_graph *g);
+GLboolean ra_select(struct ra_graph *g);
+GLboolean ra_allocate_no_spills(struct ra_graph *g);
+
+unsigned int ra_get_node_reg(struct ra_graph *g, unsigned int n);
+/** @} */
+
diff --git a/src/mesa/sources.mak b/src/mesa/sources.mak
index b2be5ba07f..11a93d47f6 100644
--- a/src/mesa/sources.mak
+++ b/src/mesa/sources.mak
@@ -247,6 +247,7 @@ PROGRAM_SOURCES = \
 	program/prog_statevars.c \
 	program/prog_uniform.c \
 	program/programopt.c \
+	program/register_allocate.c \
 	program/symbol_table.c
 
 SHADER_CXX_SOURCES = \