vc4: Add copy propagation between temps.

We put in a bunch of extra MOVs for program outputs, and this can clean
those up.  We should do uniforms, too, though.

v2: Fix missing flagging of progress when we actually optimize.  Caught by
    Aaron Watry.

src/gallium/drivers/vc4/Makefile.sources

@@ -5,6 +5,7 @@ C_SOURCES := \
 	vc4_draw.c \
 	vc4_emit.c \
 	vc4_opt_algebraic.c \
+	vc4_opt_copy_propagation.c \
 	vc4_opt_dead_code.c \
 	vc4_program.c \
 	vc4_qir.c \

src/gallium/drivers/vc4/vc4_opt_copy_propagation.c

@@ -0,0 +1,78 @@
+/*
+ * Copyright © 2014 Broadcom
+ *
+ * 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 vc4_opt_copy_propagation.c
+ *
+ * This implements simple copy propagation for QIR without control flow.
+ *
+ * For each temp, it keeps a qreg of which source it was MOVed from, if it
+ * was.  If we see that used later, we can just reuse the source value, since
+ * we know we don't have control flow, and we have SSA for our values so
+ * there's no killing to worry about.
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include "vc4_qir.h"
+
+bool
+qir_opt_copy_propagation(struct qcompile *c)
+{
+        bool progress = false;
+        struct simple_node *node;
+        bool debug = false;
+        struct qreg *movs = calloc(c->num_temps, sizeof(struct qreg));
+
+        foreach(node, &c->instructions) {
+                struct qinst *inst = (struct qinst *)node;
+
+                for (int i = 0; i < qir_get_op_nsrc(inst->op); i++) {
+                        int index = inst->src[i].index;
+                        if (inst->src[i].file == QFILE_TEMP &&
+                            movs[index].file == QFILE_TEMP) {
+                                if (debug) {
+                                        fprintf(stderr, "Copy propagate: ");
+                                        qir_dump_inst(inst);
+                                        fprintf(stderr, "\n");
+                                }
+
+                                inst->src[i] = movs[index];
+
+                                if (debug) {
+                                        fprintf(stderr, "to: ");
+                                        qir_dump_inst(inst);
+                                        fprintf(stderr, "\n");
+                                }
+
+                                progress = true;
+                        }
+                }
+
+                if (inst->op == QOP_MOV && inst->dst.file == QFILE_TEMP)
+                        movs[inst->dst.index] = inst->src[0];
+        }
+
+        free(movs);
+        return progress;
+}

src/gallium/drivers/vc4/vc4_qir.c

@@ -241,6 +241,7 @@ qir_optimize(struct qcompile *c)
                 bool progress = false;
 
                 OPTPASS(qir_opt_algebraic);
+                OPTPASS(qir_opt_copy_propagation);
                 OPTPASS(qir_opt_dead_code);
 
                 if (!progress)

src/gallium/drivers/vc4/vc4_qir.h

@@ -155,6 +155,7 @@ const char *qir_get_stage_name(enum qstage stage);
 
 void qir_optimize(struct qcompile *c);
 bool qir_opt_algebraic(struct qcompile *c);
+bool qir_opt_copy_propagation(struct qcompile *c);
 bool qir_opt_dead_code(struct qcompile *c);
 
 #define QIR_ALU1(name)                                                   \