Mesa (master): iris: Avoid replacing backing storage for buffers with no contents

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Module: Mesa
Branch: master
Commit: 97e9de17952d1382512007e4745c25b9c9106a46
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=97e9de17952d1382512007e4745c25b9c9106a46

Author: Kenneth Graunke <kenneth at whitecape.org>
Date:   Mon Nov  4 00:21:06 2019 -0800

iris: Avoid replacing backing storage for buffers with no contents

We might get asked to pitch the storage on a buffer that already has
no meaningful contents.  In this case, the existing buffer is as good
as a new one.

---

 src/gallium/drivers/iris/iris_resource.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/gallium/drivers/iris/iris_resource.c b/src/gallium/drivers/iris/iris_resource.c
index ed24d629fe5..952d6615584 100644
--- a/src/gallium/drivers/iris/iris_resource.c
+++ b/src/gallium/drivers/iris/iris_resource.c
@@ -1240,6 +1240,10 @@ iris_invalidate_resource(struct pipe_context *ctx,
    if (resource->target != PIPE_BUFFER)
       return;
 
+   /* If it's already invalidated, don't bother doing anything. */
+   if (res->valid_buffer_range.start > res->valid_buffer_range.end)
+      return;
+
    if (!resource_is_busy(ice, res)) {
       /* The resource is idle, so just mark that it contains no data and
        * keep using the same underlying buffer object.