SSBOs are read/write and this CSE pass only handles read-only variables.
---
src/glsl/opt_cse.cpp | 33 ++++++++++++++++++++++++++++++++-
1 file changed, 32 insertions(+), 1 deletion(-)
diff --git a/src/glsl/opt_cse.cpp b/src/glsl/opt_cse.cpp
index 4b8e9a0..a05ab46 100644
--- a/src/glsl/opt_cse.cpp
+++ b/src/glsl/opt_cse.cpp
@@ -245,6 +245,28 @@ contains_rvalue(ir_rvalue *haystack, ir_rvalue *needle)
}
static bool
+expression_contains_ssbo_load(ir_expression *expr)
+{
+ if (expr->operation == ir_binop_ssbo_load)
+ return true;
+
+ for (unsigned i = 0; i < expr->get_num_operands(); i++) {
+ ir_rvalue *op = expr->operands[i];
+ if (op->ir_type == ir_type_expression &&
+ expression_contains_ssbo_load(op->as_expression())) {
+ return true;
+ } else if (op->ir_type == ir_type_swizzle) {
+ ir_swizzle *swizzle = op->as_swizzle();
+ ir_expression *val = swizzle->val->as_expression();
+ if (val && expression_contains_ssbo_load(val))
+ return true;
+ }
+ }
+
+ return false;
+}
+
+static bool
is_cse_candidate(ir_rvalue *ir)
{
/* Our temporary variable assignment generation isn't ready to handle
@@ -260,7 +282,16 @@ is_cse_candidate(ir_rvalue *ir)
* to variable-index array dereferences at some point.
*/
switch (ir->ir_type) {
- case ir_type_expression:
+ case ir_type_expression: {
+ /* Skip expressions involving SSBO loads, since these operate on
+ * read-write variables, meaning that the same ssbo_load expression
+ * may return a different value if the underlying buffer storage
+ * is written in between.
+ */
+ if (expression_contains_ssbo_load(ir->as_expression()))
+ return false;
+ }
+ break;
case ir_type_texture:
break;
default:
--
1.9.1
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