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glsl: Don't copy propagate from SSBO or shared variables either

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Since SSBOs can be written by other GPU threads, copy propagating a read
can cause the value to magically change.  SSBO reads are also very
expensive, so doing it twice will be slower.

Haswell, Broadwell, and Skylake had similar results. (Skylake shown)
total instructions in shared programs: 14399120 -> 14399119 (<.01%)
instructions in affected programs: 684 -> 683 (-0.15%)
helped: 1
HURT: 0

total cycles in shared programs: 532978931 -> 532973113 (<.01%)
cycles in affected programs: 530484 -> 524666 (-1.10%)
helped: 1
HURT: 0

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Cc: mesa-stable@lists.freedesktop.org
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=106774
This commit is contained in:
Ian Romanick
2018-06-05 15:04:24 -07:00
parent 1d92d6486a
commit 461a5c899c
1 changed files with 2 additions and 0 deletions
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src/compiler/glsl/opt_copy_propagation.cpp
+2
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@@ -347,6 +347,8 @@ ir_copy_propagation_visitor::add_copy(ir_assignment *ir)
if (lhs_var != NULL && rhs_var != NULL && lhs_var != rhs_var) {
if (lhs_var->data.mode != ir_var_shader_storage &&
lhs_var->data.mode != ir_var_shader_shared &&
rhs_var->data.mode != ir_var_shader_storage &&
rhs_var->data.mode != ir_var_shader_shared &&
lhs_var->data.precise == rhs_var->data.precise) {
_mesa_hash_table_insert(acp, lhs_var, rhs_var);
}