glsl: Don't copy propagate or tree graft precise values.

This is kind of a hack.  We currently track precise requirements
by decorating ir_variables.  Propagating or grafting the RHS of an
assignment to a precise value into some other expression tree can
lose those decorations.

In the long run, it might be better to replace these ir_variable
decorations with an "exact" decoration on ir_expression nodes,
similar to what NIR does.

In the short run, this is probably good enough.  It preserves
enough information for glsl_to_nir to generate "exact" decorations,
and NIR will then handle optimizing these expressions reasonably.

Fixes ES31-CTS.gpu_shader5.precise_qualifier.

v2: Drop invariant handling, as it shouldn't be necessary (caught
    by Jason Ekstrand).

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

1 files changed, 2 insertions, 1 deletions

diff --git a/src/compiler/glsl/opt_copy_propagation.cpp b/src/compiler/glsl/opt_copy_propagation.cpp
index 310708d..ae62921 100644
--- a/src/compiler/glsl/opt_copy_propagation.cpp
+++ b/src/compiler/glsl/opt_copy_propagation.cpp
@@ -331,7 +331,8 @@ ir_copy_propagation_visitor::add_copy(ir_assignment *ir)
 	 ir->condition = new(ralloc_parent(ir)) ir_constant(false);
 	 this->progress = true;
       } else if (lhs_var->data.mode != ir_var_shader_storage &&
-                 lhs_var->data.mode != ir_var_shader_shared) {
+                 lhs_var->data.mode != ir_var_shader_shared &&
+                 lhs_var->data.precise == rhs_var->data.precise) {
 	 entry = new(this->acp) acp_entry(lhs_var, rhs_var);
 	 this->acp->push_tail(entry);
       }