i965/fs: Add support for copy propagation.

We could do more by handling abs/negate and non-GRF sources, but this is
a good start.  Improves tropics performance 0.30% +/- .17% (n=43).

shader-db results:
Total instructions: 208032 -> 207184
60/1246 programs affected (4.8%)
23286 -> 22438 instructions in affected programs (3.6% reduction)

Reviewed-by: Kenneth Graunke <[email protected]>

1 files changed, 137 insertions, 0 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_fs_copy_propagation.cpp b/src/mesa/drivers/dri/i965/brw_fs_copy_propagation.cpp
new file mode 100644
index 00000000000..23960514bf0
--- /dev/null
+++ b/src/mesa/drivers/dri/i965/brw_fs_copy_propagation.cpp
@@ -0,0 +1,137 @@
+/*
+ * Copyright © 2012 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.
+ */
+
+#include "brw_fs.h"
+#include "brw_fs_cfg.h"
+
+namespace { /* avoid conflict with opt_copy_propagation_elements */
+struct acp_entry : public exec_node {
+   fs_reg dst;
+   fs_reg src;
+};
+}
+
+/** @file brw_fs_copy_propagation.cpp
+ *
+ * Support for local copy propagation by walking the list of instructions
+ * and maintaining the ACP table of available copies for propagation.
+ *
+ * See Muchnik's Advanced Compiler Design and Implementation, section
+ * 12.5 (p356).
+ */
+
+/* Walks a basic block and does copy propagation on it using the acp
+ * list.
+ */
+bool
+fs_visitor::opt_copy_propagate_local(void *mem_ctx,
+				     fs_bblock *block, exec_list *acp)
+{
+   bool progress = false;
+
+   for (fs_inst *inst = block->start;
+	inst != block->end->next;
+	inst = (fs_inst *)inst->next) {
+
+      /* Try propagating into this instruction. */
+      foreach_list(entry_node, acp) {
+	 acp_entry *entry = (acp_entry *)entry_node;
+
+	 for (int i = 0; i < 3; i++) {
+	    if (inst->src[i].file == entry->dst.file &&
+		inst->src[i].reg == entry->dst.reg &&
+		inst->src[i].reg_offset == entry->dst.reg_offset) {
+	       inst->src[i].reg = entry->src.reg;
+	       inst->src[i].reg_offset = entry->src.reg_offset;
+	       progress = true;
+	    }
+	 }
+      }
+
+      /* kill the destination from the ACP */
+      if (inst->dst.file == GRF) {
+	 int start_offset = inst->dst.reg_offset;
+	 int end_offset = start_offset + inst->regs_written();
+
+	 foreach_list_safe(entry_node, acp) {
+	    acp_entry *entry = (acp_entry *)entry_node;
+
+	    if (entry->dst.file == GRF &&
+		entry->dst.reg == inst->dst.reg &&
+		entry->dst.reg_offset >= start_offset &&
+		entry->dst.reg_offset < end_offset) {
+	       entry->remove();
+	       continue;
+	    }
+	    if (entry->src.file == GRF &&
+		entry->src.reg == inst->dst.reg &&
+		entry->src.reg_offset >= start_offset &&
+		entry->src.reg_offset < end_offset) {
+	       entry->remove();
+	    }
+	 }
+      }
+
+      /* If this instruction is a raw copy, add it to the ACP. */
+      if (inst->opcode == BRW_OPCODE_MOV &&
+	  inst->dst.file == GRF &&
+	  inst->src[0].file == GRF &&
+	  (inst->src[0].reg != inst->dst.reg ||
+	   inst->src[0].reg_offset != inst->dst.reg_offset) &&
+	  inst->src[0].type == inst->dst.type &&
+	  !inst->saturate &&
+	  !inst->predicated &&
+	  !inst->force_uncompressed &&
+	  !inst->force_sechalf &&
+	  inst->src[0].smear == -1 &&
+	  !inst->src[0].abs &&
+	  !inst->src[0].negate) {
+	 acp_entry *entry = ralloc(mem_ctx, acp_entry);
+	 entry->dst = inst->dst;
+	 entry->src = inst->src[0];
+	 acp->push_tail(entry);
+      }
+   }
+
+   return progress;
+}
+
+bool
+fs_visitor::opt_copy_propagate()
+{
+   bool progress = false;
+   void *mem_ctx = ralloc_context(this->mem_ctx);
+
+   fs_cfg cfg(this);
+
+   for (int b = 0; b < cfg.num_blocks; b++) {
+      fs_bblock *block = cfg.blocks[b];
+      exec_list acp;
+
+      progress = opt_copy_propagate_local(mem_ctx, block, &acp) || progress;
+   }
+
+   ralloc_free(mem_ctx);
+
+   return progress;
+}