glsl: Handle conditional discards in lower_discard_flow().

This pass wasn't prepared to handle conditional discards.

Instead of initializing the "discarded" temporary to "true", set it to
the condition.  Then, refer to the variable for the condition, to avoid
duplicating the expression tree.

Signed-off-by: Kenneth Graunke <[email protected]>
Reviewed-by: Connor Abbott <[email protected]>
Reviewed-by: Matt Turner <[email protected]>
Reviewed-by: Eric Anholt <[email protected]>

1 files changed, 8 insertions, 1 deletions

diff --git a/src/glsl/lower_discard_flow.cpp b/src/glsl/lower_discard_flow.cpp
index 1bc56d79e98..ee45bf22155 100644
--- a/src/glsl/lower_discard_flow.cpp
+++ b/src/glsl/lower_discard_flow.cpp
@@ -90,7 +90,14 @@ ir_visitor_status
 lower_discard_flow_visitor::visit_enter(ir_discard *ir)
 {
    ir_dereference *lhs = new(mem_ctx) ir_dereference_variable(discarded);
-   ir_rvalue *rhs = new(mem_ctx) ir_constant(true);
+   ir_rvalue *rhs;
+   if (ir->condition) {
+      /* discarded <- condition, use (var_ref discarded) as the condition */
+      rhs = ir->condition;
+      ir->condition = new(mem_ctx) ir_dereference_variable(discarded);
+   } else {
+      rhs = new(mem_ctx) ir_constant(true);
+   }
    ir_assignment *assign = new(mem_ctx) ir_assignment(lhs, rhs);
    ir->insert_before(assign);