nir: Add a worklist helper structure

A worklist is a common concept in optimizations.  This adds a structure
that we can reuse for many different types of optimizations.

Reviewed-by: Connor Abbott <cwabbott0@gmail.com>

3 files changed, 237 insertions, 0 deletions

diff --git a/src/glsl/Makefile.sources b/src/glsl/Makefile.sources
index 006e947218..a951ca7dbc 100644
--- a/src/glsl/Makefile.sources
+++ b/src/glsl/Makefile.sources
@@ -50,6 +50,8 @@ NIR_FILES = \
 	$(GLSL_SRCDIR)/nir/nir_split_var_copies.c \
 	$(GLSL_SRCDIR)/nir/nir_to_ssa.c \
 	$(GLSL_SRCDIR)/nir/nir_validate.c \
+	$(GLSL_SRCDIR)/nir/nir_worklist.c \
+	$(GLSL_SRCDIR)/nir/nir_worklist.h \
 	$(GLSL_SRCDIR)/nir/nir_types.cpp \
 	$(GLSL_SRCDIR)/nir/glsl_to_nir.cpp \
 	$(NIR_GENERATED_FILES)
diff --git a/src/glsl/nir/nir_worklist.c b/src/glsl/nir/nir_worklist.c
new file mode 100644
index 0000000000..a8baae9375
--- /dev/null
+++ b/src/glsl/nir/nir_worklist.c
@@ -0,0 +1,144 @@
+/*
+ * Copyright © 2014 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:
+ *    Jason Ekstrand (jason@jlekstrand.net)
+ *
+ */
+
+#include "nir_worklist.h"
+
+void
+nir_block_worklist_init(nir_block_worklist *w, unsigned num_blocks,
+                        void *mem_ctx)
+{
+   w->size = num_blocks;
+   w->count = 0;
+   w->start = 0;
+
+   w->blocks_present = rzalloc_array(mem_ctx, BITSET_WORD,
+                                     BITSET_WORDS(num_blocks));
+   w->blocks = ralloc_array(mem_ctx, nir_block *, num_blocks);
+}
+
+void
+nir_block_worklist_fini(nir_block_worklist *w)
+{
+   ralloc_free(w->blocks_present);
+   ralloc_free(w->blocks);
+}
+
+static bool
+worklist_add_block(nir_block *block, void *w)
+{
+   nir_block_worklist_push_tail(w, block);
+
+   return true;
+}
+
+void
+nir_block_worklist_add_all(nir_block_worklist *w, nir_function_impl *impl)
+{
+   nir_foreach_block(impl, worklist_add_block, w);
+}
+
+void
+nir_block_worklist_push_head(nir_block_worklist *w, nir_block *block)
+{
+   /* Pushing a block we already have is a no-op */
+   if (BITSET_TEST(w->blocks_present, block->index))
+      return;
+
+   assert(w->count < w->size);
+
+   if (w->start == 0)
+      w->start = w->size - 1;
+   else
+      w->start--;
+
+   w->count++;
+
+   w->blocks[w->start] = block;
+   BITSET_SET(w->blocks_present, block->index);
+}
+
+nir_block *
+nir_block_worklist_peek_head(nir_block_worklist *w)
+{
+   assert(w->count > 0);
+
+   return w->blocks[w->start];
+}
+
+nir_block *
+nir_block_worklist_pop_head(nir_block_worklist *w)
+{
+   assert(w->count > 0);
+
+   unsigned head = w->start;
+
+   w->start = (w->start + 1) % w->size;
+   w->count--;
+
+   BITSET_CLEAR(w->blocks_present, w->blocks[head]->index);
+   return w->blocks[head];
+}
+
+void
+nir_block_worklist_push_tail(nir_block_worklist *w, nir_block *block)
+{
+   /* Pushing a block we already have is a no-op */
+   if (BITSET_TEST(w->blocks_present, block->index))
+      return;
+
+   assert(w->count < w->size);
+
+   w->count++;
+
+   unsigned tail = w->start = (w->start + w->count - 1) % w->size;
+
+   w->blocks[tail] = block;
+   BITSET_SET(w->blocks_present, block->index);
+}
+
+nir_block *
+nir_block_worklist_peek_tail(nir_block_worklist *w)
+{
+   assert(w->count > 0);
+
+   unsigned tail = w->start = (w->start + w->count - 1) % w->size;
+
+   return w->blocks[tail];
+}
+
+nir_block *
+nir_block_worklist_pop_tail(nir_block_worklist *w)
+{
+   assert(w->count > 0);
+
+   unsigned tail = w->start = (w->start + w->count - 1) % w->size;
+
+   w->count--;
+
+   BITSET_CLEAR(w->blocks_present, w->blocks[tail]->index);
+   return w->blocks[tail];
+}
diff --git a/src/glsl/nir/nir_worklist.h b/src/glsl/nir/nir_worklist.h
new file mode 100644
index 0000000000..d5a8568e42
--- /dev/null
+++ b/src/glsl/nir/nir_worklist.h
@@ -0,0 +1,91 @@
+/*
+ * Copyright © 2014 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:
+ *    Jason Ekstrand (jason@jlekstrand.net)
+ *
+ */
+
+#pragma once
+
+#ifndef _NIR_WORKLIST_
+#define _NIR_WORKLIST_
+
+#include "nir.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/** Represents a double-ended queue of unique blocks
+ *
+ * The worklist datastructure guarantees that eacy block is in the queue at
+ * most once.  Pushing a block onto either end of the queue is a no-op if
+ * the block is already in the queue.  In order for this to work, the
+ * caller must ensure that the blocks are properly indexed.
+ */
+typedef struct {
+   /* The total size of the worklist */
+   unsigned size;
+
+   /* The number of blocks currently in the worklist */
+   unsigned count;
+
+   /* The offset in the array of blocks at which the list starts */
+   unsigned start;
+
+   /* A bitset of all of the blocks currently present in the worklist */
+   BITSET_WORD *blocks_present;
+
+   /* The actual worklist */
+   nir_block **blocks;
+} nir_block_worklist;
+
+void nir_block_worklist_init(nir_block_worklist *w, unsigned num_blocks,
+                             void *mem_ctx);
+void nir_block_worklist_fini(nir_block_worklist *w);
+
+void nir_block_worklist_add_all(nir_block_worklist *w, nir_function_impl *impl);
+
+static inline bool
+nir_block_worklist_is_empty(const nir_block_worklist *w)
+{
+   return w->count == 0;
+}
+
+void nir_block_worklist_push_head(nir_block_worklist *w, nir_block *block);
+
+nir_block *nir_block_worklist_peek_head(nir_block_worklist *w);
+
+nir_block *nir_block_worklist_pop_head(nir_block_worklist *w);
+
+void nir_block_worklist_push_tail(nir_block_worklist *w, nir_block *block);
+
+nir_block *nir_block_worklist_peek_tail(nir_block_worklist *w);
+
+nir_block *nir_block_worklist_pop_tail(nir_block_worklist *w);
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+#endif /* _NIR_WORKLIST_ */