i965/fs: Add pass to propagate conditional modifiers.

total instructions in shared programs: 5974160 -> 5959463 (-0.25%)
instructions in affected programs:     1743737 -> 1729040 (-0.84%)
GAINED:                                0
LOST:                                  12

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/mesa/drivers/dri/i965/Makefile.sources

@@ -39,6 +39,7 @@ i965_FILES = \
 	brw_ff_gs_emit.c \
 	brw_ff_gs.h \
 	brw_fs_channel_expressions.cpp \
+	brw_fs_cmod_propagation.cpp \
 	brw_fs_copy_propagation.cpp \
 	brw_fs.cpp \
 	brw_fs_cse.cpp \

src/mesa/drivers/dri/i965/brw_fs.cpp

@@ -3583,6 +3583,7 @@ fs_visitor::optimize()
       OPT(opt_cse);
       OPT(opt_copy_propagate);
       OPT(opt_peephole_predicated_break);
+      OPT(opt_cmod_propagation);
       OPT(dead_code_eliminate);
       OPT(opt_peephole_sel);
       OPT(dead_control_flow_eliminate, this);

src/mesa/drivers/dri/i965/brw_fs.h

@@ -540,6 +540,7 @@ public:
    bool opt_peephole_sel();
    bool opt_peephole_predicated_break();
    bool opt_saturate_propagation();
+   bool opt_cmod_propagation();
    void emit_bool_to_cond_code(ir_rvalue *condition);
    void emit_if_gen6(ir_if *ir);
    void emit_unspill(bblock_t *block, fs_inst *inst, fs_reg reg,

src/mesa/drivers/dri/i965/brw_fs_cmod_propagation.cpp

@@ -0,0 +1,98 @@
+/*
+ * 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.
+ */
+
+#include "brw_fs.h"
+#include "brw_fs_live_variables.h"
+#include "brw_cfg.h"
+
+/** @file brw_fs_cmod_propagation.cpp
+ *
+ * Implements a pass that propagates the conditional modifier from a CMP x 0.0
+ * instruction into the instruction that generated x. For instance, in this
+ * sequence
+ *
+ *    add(8)          g70<1>F    g69<8,8,1>F    4096F
+ *    cmp.ge.f0(8)    null       g70<8,8,1>F    0F
+ *
+ * we can do the comparison as part of the ADD instruction directly:
+ *
+ *    add.ge.f0(8)    g70<1>F    g69<8,8,1>F    4096F
+ */
+
+static bool
+opt_cmod_propagation_local(fs_visitor *v, bblock_t *block)
+{
+   bool progress = false;
+   int ip = block->end_ip + 1;
+
+   foreach_inst_in_block_reverse_safe(fs_inst, inst, block) {
+      ip--;
+
+      if (inst->opcode != BRW_OPCODE_CMP ||
+          inst->predicate != BRW_PREDICATE_NONE ||
+          !inst->dst.is_null() ||
+          inst->src[0].file != GRF ||
+          inst->src[0].abs ||
+          inst->src[0].negate ||
+          !inst->src[1].is_zero())
+         continue;
+
+      foreach_inst_in_block_reverse_starting_from(fs_inst, scan_inst, inst,
+                                                  block) {
+         if (scan_inst->overwrites_reg(inst->src[0])) {
+            if (scan_inst->is_partial_write() ||
+                scan_inst->dst.reg_offset != inst->src[0].reg_offset)
+               break;
+
+            if (scan_inst->can_do_cmod() &&
+                (scan_inst->conditional_mod == BRW_CONDITIONAL_NONE ||
+                 scan_inst->conditional_mod == inst->conditional_mod)) {
+               scan_inst->conditional_mod = inst->conditional_mod;
+               inst->remove(block);
+               progress = true;
+            }
+            break;
+         }
+
+         if (scan_inst->reads_flag() || scan_inst->writes_flag())
+            break;
+      }
+   }
+
+   return progress;
+}
+
+bool
+fs_visitor::opt_cmod_propagation()
+{
+   bool progress = false;
+
+   foreach_block_reverse(block, cfg) {
+      progress = opt_cmod_propagation_local(this, block) || progress;
+   }
+
+   if (progress)
+      invalidate_live_intervals();
+
+   return progress;
+}