Mesa (master): panfrost/midgard: Fix crash with unused SSA values

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Module: Mesa
Branch: master
Commit: 30adeb7a5358d611e01829b000bab6dfee4abed0
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=30adeb7a5358d611e01829b000bab6dfee4abed0

Author: Alyssa Rosenzweig <alyssa.rosenzweig at collabora.com>
Date:   Thu Jun  6 08:15:23 2019 -0700

panfrost/midgard: Fix crash with unused SSA values

Crash introduced in "b38dab101ca7e0896255dccbd85fd510c47d84d1" but not
adding a Fixes tag since it's our bug anyway.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig at collabora.com>

---

 src/gallium/drivers/panfrost/midgard/midgard_compile.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/gallium/drivers/panfrost/midgard/midgard_compile.c b/src/gallium/drivers/panfrost/midgard/midgard_compile.c
index dd86e8bceee..032f4a91196 100644
--- a/src/gallium/drivers/panfrost/midgard/midgard_compile.c
+++ b/src/gallium/drivers/panfrost/midgard/midgard_compile.c
@@ -1688,6 +1688,10 @@ embedded_to_inline_constant(compiler_context *ctx)
 static void
 map_ssa_to_alias(compiler_context *ctx, int *ref)
 {
+        /* Sign is used quite deliberately for unused */
+        if (*ref < 0)
+                return;
+
         unsigned int alias = (uintptr_t) _mesa_hash_table_u64_search(ctx->ssa_to_alias, *ref + 1);
 
         if (alias) {