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authorJordan Justen <jordan.l.justen@intel.com>2015-10-19 23:13:09 -0700
committerJordan Justen <jordan.l.justen@intel.com>2015-10-22 00:36:37 -0700
commit627c15cde46a76e9bce4425646c5caba11788ec4 (patch)
tree7a9d7820ae9182160b4c78e380c6728f2317cb30
parent13a5805b646b19fd9c155d5c586ad1967d7d9e00 (diff)
i965/fs: Disable CSE optimization for untyped & typed surface reads
An untyped surface read is volatile because it might be affected by a write. In the ES31-CTS.compute_shader.resources-max test, two back to back read/modify/writes of an SSBO variable looked something like this: r1 = untyped_surface_read(ssbo_float) r2 = r1 + 1 untyped_surface_write(ssbo_float, r2) r3 = untyped_surface_read(ssbo_float) r4 = r3 + 1 untyped_surface_write(ssbo_float, r4) And after CSE, we had: r1 = untyped_surface_read(ssbo_float) r2 = r1 + 1 untyped_surface_write(ssbo_float, r2) r4 = r1 + 1 untyped_surface_write(ssbo_float, r4) Signed-off-by: Jordan Justen <jordan.l.justen@intel.com> Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
-rw-r--r--src/mesa/drivers/dri/i965/brw_fs_cse.cpp3
-rw-r--r--src/mesa/drivers/dri/i965/brw_shader.cpp14
-rw-r--r--src/mesa/drivers/dri/i965/brw_shader.h6
3 files changed, 22 insertions, 1 deletions
diff --git a/src/mesa/drivers/dri/i965/brw_fs_cse.cpp b/src/mesa/drivers/dri/i965/brw_fs_cse.cpp
index c7628dcc2f4..3a28c8d591d 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_cse.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_cse.cpp
@@ -93,7 +93,8 @@ is_expression(const fs_visitor *v, const fs_inst *const inst)
case SHADER_OPCODE_LOAD_PAYLOAD:
return !inst->is_copy_payload(v->alloc);
default:
- return inst->is_send_from_grf() && !inst->has_side_effects();
+ return inst->is_send_from_grf() && !inst->has_side_effects() &&
+ !inst->is_volatile();
}
}
diff --git a/src/mesa/drivers/dri/i965/brw_shader.cpp b/src/mesa/drivers/dri/i965/brw_shader.cpp
index 6f6f77ab583..204935641f3 100644
--- a/src/mesa/drivers/dri/i965/brw_shader.cpp
+++ b/src/mesa/drivers/dri/i965/brw_shader.cpp
@@ -987,6 +987,20 @@ backend_instruction::has_side_effects() const
}
}
+bool
+backend_instruction::is_volatile() const
+{
+ switch (opcode) {
+ case SHADER_OPCODE_UNTYPED_SURFACE_READ:
+ case SHADER_OPCODE_UNTYPED_SURFACE_READ_LOGICAL:
+ case SHADER_OPCODE_TYPED_SURFACE_READ:
+ case SHADER_OPCODE_TYPED_SURFACE_READ_LOGICAL:
+ return true;
+ default:
+ return false;
+ }
+}
+
#ifndef NDEBUG
static bool
inst_is_in_block(const bblock_t *block, const backend_instruction *inst)
diff --git a/src/mesa/drivers/dri/i965/brw_shader.h b/src/mesa/drivers/dri/i965/brw_shader.h
index 51b059fcaa1..6a2dfc9bbb6 100644
--- a/src/mesa/drivers/dri/i965/brw_shader.h
+++ b/src/mesa/drivers/dri/i965/brw_shader.h
@@ -115,6 +115,12 @@ struct backend_instruction : public exec_node {
* optimize these out unless you know what you are doing.
*/
bool has_side_effects() const;
+
+ /**
+ * True if the instruction might be affected by side effects of other
+ * instructions.
+ */
+ bool is_volatile() const;
#else
struct backend_instruction {
struct exec_node link;