Import Mesa 13.0.2

1 files changed, 49 insertions, 57 deletions

diff --git a/lib/mesa/src/gallium/drivers/vc4/vc4_opt_dead_code.c b/lib/mesa/src/gallium/drivers/vc4/vc4_opt_dead_code.c
index 9e79a2d1b..1838c394f 100644
--- a/lib/mesa/src/gallium/drivers/vc4/vc4_opt_dead_code.c
+++ b/lib/mesa/src/gallium/drivers/vc4/vc4_opt_dead_code.c
@@ -24,11 +24,15 @@
 /**
  * @file vc4_opt_dead_code.c
  *
- * This is a simmple dead code eliminator for QIR with no control flow.
+ * This is a simple dead code eliminator for SSA values in QIR.
  *
- * It walks from the bottom of the instruction list, removing instructions
- * with a destination that is never used, and marking the sources of non-dead
- * instructions as used.
+ * It walks all the instructions finding what temps are used, then walks again
+ * to remove instructions writing unused temps.
+ *
+ * This is an inefficient implementation if you have long chains of
+ * instructions where the entire chain is dead, but we expect those to have
+ * been eliminated at the NIR level, and here we're just cleaning up small
+ * problems produced by NIR->QIR.
  */
 
 #include "vc4_qir.h"
@@ -82,25 +86,47 @@ qir_opt_dead_code(struct vc4_compile *c)
 {
         bool progress = false;
         bool *used = calloc(c->num_temps, sizeof(bool));
-        bool sf_used = false;
-        /* Whether we're eliminating texture setup currently. */
-        bool dce_tex = false;
-
-        struct list_head *node, *t;
-        for (node = c->instructions.prev, t = node->prev;
-             &c->instructions != node;
-             node = t, t = t->prev) {
-                struct qinst *inst = (struct qinst *)node;
-
-                if (inst->dst.file == QFILE_TEMP &&
-                    !used[inst->dst.index] &&
-                    !inst->sf &&
-                    (!qir_has_side_effects(c, inst) ||
-                     inst->op == QOP_TEX_RESULT) &&
-                    !has_nonremovable_reads(c, inst)) {
-                        if (inst->op == QOP_TEX_RESULT) {
-                                dce_tex = true;
-                                c->num_texture_samples--;
+
+        qir_for_each_inst_inorder(inst, c) {
+                for (int i = 0; i < qir_get_op_nsrc(inst->op); i++) {
+                        if (inst->src[i].file == QFILE_TEMP)
+                                used[inst->src[i].index] = true;
+                }
+        }
+
+        qir_for_each_block(block, c) {
+                qir_for_each_inst_safe(inst, block) {
+                        if (inst->dst.file != QFILE_NULL &&
+                            !(inst->dst.file == QFILE_TEMP &&
+                              !used[inst->dst.index])) {
+                                continue;
+                        }
+
+                        if (qir_has_side_effects(c, inst))
+                                continue;
+
+                        if (inst->sf ||
+                            has_nonremovable_reads(c, inst)) {
+                                /* If we can't remove the instruction, but we
+                                 * don't need its destination value, just
+                                 * remove the destination.  The register
+                                 * allocator would trivially color it and it
+                                 * wouldn't cause any register pressure, but
+                                 * it's nicer to read the QIR code without
+                                 * unused destination regs.
+                                 */
+                                if (inst->dst.file == QFILE_TEMP) {
+                                        if (debug) {
+                                                fprintf(stderr,
+                                                        "Removing dst from: ");
+                                                qir_dump_inst(c, inst);
+                                                fprintf(stderr, "\n");
+                                        }
+                                        c->defs[inst->dst.index] = NULL;
+                                        inst->dst.file = QFILE_NULL;
+                                        progress = true;
+                                }
+                                continue;
                         }
 
                         for (int i = 0; i < qir_get_op_nsrc(inst->op); i++) {
@@ -119,40 +145,6 @@ qir_opt_dead_code(struct vc4_compile *c)
                         progress = true;
                         continue;
                 }
-
-                if (qir_depends_on_flags(inst))
-                        sf_used = true;
-                if (inst->sf) {
-                        if (!sf_used) {
-                                if (debug) {
-                                        fprintf(stderr, "Removing SF on: ");
-                                        qir_dump_inst(c, inst);
-                                        fprintf(stderr, "\n");
-                                }
-
-                                inst->sf = false;
-                                progress = true;
-                        }
-                        sf_used = false;
-                }
-
-                if (inst->op == QOP_TEX_RESULT)
-                        dce_tex = false;
-
-                if (dce_tex && (inst->op == QOP_TEX_S ||
-                                inst->op == QOP_TEX_T ||
-                                inst->op == QOP_TEX_R ||
-                                inst->op == QOP_TEX_B ||
-                                inst->op == QOP_TEX_DIRECT)) {
-                        dce(c, inst);
-                        progress = true;
-                        continue;
-                }
-
-                for (int i = 0; i < qir_get_op_nsrc(inst->op); i++) {
-                        if (inst->src[i].file == QFILE_TEMP)
-                                used[inst->src[i].index] = true;
-                }
         }
 
         free(used);