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

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

diff --git a/src/compiler/glsl/opt_copy_propagation.cpp b/src/compiler/glsl/opt_copy_propagation.cpp
index 6220aa86da9d5071b5961e7a49e5e4c24d47dc50..206dffe4f1c033eb427e1ce25b116aa157eb152b 100644 (file)
--- a/src/compiler/glsl/opt_copy_propagation.cpp
+++ b/src/compiler/glsl/opt_copy_propagation.cpp
@@ -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);
       }