From 5dfea83ee6bf85fb3962679d043eb06b33bfd4c1 Mon Sep 17 00:00:00 2001 From: Iago Toral Quiroga Date: Fri, 24 Apr 2015 11:15:48 +0200 Subject: [PATCH] glsl: Don't do constant variable on buffer variables Since the backing storage for these is shared we cannot ensure that the value won't change by writes from other threads. Normally SSBO accesses are not guaranteed to be syncronized with other threads, except when memoryBarrier is used. So, we might be able to optimize some SSBO accesses, but for now we always take the safe path and emit the SSBO access. Reviewed-by: Jordan Justen --- src/glsl/opt_constant_variable.cpp | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/src/glsl/opt_constant_variable.cpp b/src/glsl/opt_constant_variable.cpp index 7222eb92a7d..7aaaeedf98d 100644 --- a/src/glsl/opt_constant_variable.cpp +++ b/src/glsl/opt_constant_variable.cpp @@ -115,6 +115,13 @@ ir_constant_variable_visitor::visit_enter(ir_assignment *ir) if (!var) return visit_continue; + /* Ignore buffer variables, since the underlying storage is shared + * and we can't be sure that this variable won't be written by another + * thread. + */ + if (var->data.mode == ir_var_shader_storage) + return visit_continue; + constval = ir->rhs->constant_expression_value(); if (!constval) return visit_continue; -- 2.30.2