From 0b1111d985714816fad20c99b4e6ea762df17b46 Mon Sep 17 00:00:00 2001 From: Iago Toral Quiroga Date: Fri, 24 Apr 2015 11:14:17 +0200 Subject: glsl: Don't do constant propagation 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_propagation.cpp | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/src/glsl/opt_constant_propagation.cpp b/src/glsl/opt_constant_propagation.cpp index 90cc0c89b6..10be8e800f 100644 --- a/src/glsl/opt_constant_propagation.cpp +++ b/src/glsl/opt_constant_propagation.cpp @@ -444,6 +444,14 @@ ir_constant_propagation_visitor::add_constant(ir_assignment *ir) if (!deref->var->type->is_vector() && !deref->var->type->is_scalar()) return; + /* We can't do copy propagation on buffer variables, since the underlying + * memory storage is shared across multiple threads we can't be sure that + * the variable value isn't modified between this assignment and the next + * instruction where its value is read. + */ + if (deref->var->data.mode == ir_var_shader_storage) + return; + entry = new(this->mem_ctx) acp_entry(deref->var, ir->write_mask, constant); this->acp->push_tail(entry); } -- cgit v1.2.3