From: Eric Anholt <eric@anholt.net>
Date: Fri, 3 Jun 2016 22:06:52 +0000 (-0700)
Subject: vc4: DCE instructions with a NULL destination.
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=aa76ba6f2fb0d6438b2b652d9fa466b6cf77fa31;p=mesa.git

vc4: DCE instructions with a NULL destination.

I'm going to add an optimization for redundant SF update removal, which
will just remove the SF and leave us (in many cases) with an instruction
with a NULL destination and no side effects.  Rather than teaching that
pass whether the whole instruction can be removed, leave that
responsibility to this pass.
---

diff --git a/src/gallium/drivers/vc4/vc4_opt_dead_code.c b/src/gallium/drivers/vc4/vc4_opt_dead_code.c
index d3562ee947e..ad51ed779ea 100644
--- a/src/gallium/drivers/vc4/vc4_opt_dead_code.c
+++ b/src/gallium/drivers/vc4/vc4_opt_dead_code.c
@@ -86,8 +86,9 @@ qir_opt_dead_code(struct vc4_compile *c)
 
         list_for_each_entry_safe_rev(struct qinst, inst, &c->instructions,
                                      link) {
-                if (inst->dst.file == QFILE_TEMP &&
-                    !used[inst->dst.index] &&
+                if ((inst->dst.file == QFILE_NULL ||
+                     (inst->dst.file == QFILE_TEMP &&
+                      !used[inst->dst.index])) &&
                     !inst->sf &&
                     !qir_has_side_effects(c, inst) &&
                     !has_nonremovable_reads(c, inst)) {