[Command buffer] Feedback loop detection between texture and framebuffer attachments

gpu/command_buffer/service/gles2_cmd_decoder.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "gpu/command_buffer/service/gles2_cmd_decoder.h"
 
 #include <limits.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <stdio.h>
@@ skipping 1303 matching lines @@
   // -1. If the current program is not valid generates the appropriate GL
   // error. Returns true if the current program is in a usable state and
   // location is not -1.
   bool CheckCurrentProgramForUniform(GLint location, const char* function_name);
 
   // Checks if the current program samples a texture that is also the color
   // image of the current bound framebuffer, i.e., the source and destination
   // of the draw operation are the same.
   bool CheckDrawingFeedbackLoops();
 
+  // Helper for CheckDrawingFeedbackLoops. Returns true if the attachment is
+  // the same one where it samples from during drawing.
+  bool CheckDrawingFeedbackLoopsHelper(
+    const Framebuffer::Attachment* attachment);
+
   bool SupportsDrawBuffers() const;
 
   // Checks if a draw buffer's format and its corresponding fragment shader
   // output's type are compatible, i.e., a signed integer typed variable is
   // incompatible with a float or unsigned integer buffer.
   // If incompaticle, generates an INVALID_OPERATION to avoid undefined buffer
   // contents and return false.
   // Otherwise, filter out the draw buffers that are not written to but are not
   // NONE through DrawBuffers, to be on the safe side. Return true.
   bool ValidateAndAdjustDrawBuffers(const char* function_name);
@@ skipping 7304 matching lines @@
 
 bool GLES2DecoderImpl::CheckCurrentProgramForUniform(
     GLint location, const char* function_name) {
   if (!CheckCurrentProgram(function_name)) {
     return false;
   }
   return !state_.current_program->IsInactiveUniformLocationByFakeLocation(
       location);
 }
 
-bool GLES2DecoderImpl::CheckDrawingFeedbackLoops() {
-  Framebuffer* framebuffer = GetFramebufferInfoForTarget(GL_FRAMEBUFFER);
-  if (!framebuffer)
-    return false;
-  const Framebuffer::Attachment* attachment =
-      framebuffer->GetAttachment(GL_COLOR_ATTACHMENT0);
-  if (!attachment)
-    return false;
-
+bool GLES2DecoderImpl::CheckDrawingFeedbackLoopsHelper(
+    const Framebuffer::Attachment* attachment) {
   DCHECK(state_.current_program.get());
   const Program::SamplerIndices& sampler_indices =
       state_.current_program->sampler_indices();
   for (size_t ii = 0; ii < sampler_indices.size(); ++ii) {
     const Program::UniformInfo* uniform_info =
         state_.current_program->GetUniformInfo(sampler_indices[ii]);
     DCHECK(uniform_info);
     for (size_t jj = 0; jj < uniform_info->texture_units.size(); ++jj) {
       GLuint texture_unit_index = uniform_info->texture_units[jj];
       if (texture_unit_index >= state_.texture_units.size())
         continue;
       TextureUnit& texture_unit = state_.texture_units[texture_unit_index];
       TextureRef* texture_ref =
           texture_unit.GetInfoForSamplerType(uniform_info->type).get();
       if (attachment->IsTexture(texture_ref))
         return true;
     }
   }
   return false;
 }
 
+bool GLES2DecoderImpl::CheckDrawingFeedbackLoops() {
+  if (!SupportsDrawBuffers()) {
+    Framebuffer* framebuffer = GetFramebufferInfoForTarget(GL_FRAMEBUFFER);
+    if (!framebuffer)
+      return false;
+    const Framebuffer::Attachment* attachment =
+        framebuffer->GetAttachment(GL_COLOR_ATTACHMENT0);
+    if (!attachment)
+      return false;
+    return CheckDrawingFeedbackLoopsHelper(attachment);
+  } else {
+    Framebuffer* framebuffer = GetFramebufferInfoForTarget(GL_DRAW_FRAMEBUFFER);
+    if (!framebuffer)
+      return false;
+    for (uint32_t ii = 0; ii < group_->max_draw_buffers(); ++ii) {
+      GLenum drawbuffer = static_cast<GLenum>(GL_DRAW_BUFFER0 + ii);
+      if (framebuffer->GetDrawBuffer(drawbuffer) == GL_NONE)
+        continue;
+      GLenum attachment = static_cast<GLenum>(GL_COLOR_ATTACHMENT0 + ii);
+      const Framebuffer::Attachment* draw_buffer =
+          framebuffer->GetAttachment(attachment);
+      if (!draw_buffer)
+        continue;
+      if (CheckDrawingFeedbackLoopsHelper(draw_buffer))
+        return true;
+    }
+    return false;
+  }
+}
+
 bool GLES2DecoderImpl::SupportsDrawBuffers() const {
   return feature_info_->IsWebGL1OrES2Context() ?
       feature_info_->feature_flags().ext_draw_buffers : true;
 }
 
 bool GLES2DecoderImpl::ValidateAndAdjustDrawBuffers(const char* func_name) {
   if (!SupportsDrawBuffers()) {
     return true;
   }
   Framebuffer* framebuffer = framebuffer_state_.bound_draw_framebuffer.get();
@@ skipping 10107 matching lines @@
 }
 
 // Include the auto-generated part of this file. We split this because it means
 // we can easily edit the non-auto generated parts right here in this file
 // instead of having to edit some template or the code generator.
 #include "base/macros.h"
 #include "gpu/command_buffer/service/gles2_cmd_decoder_autogen.h"
 
 }  // namespace gles2
 }  // namespace gpu