From b558cd4af4469253c3b7101b648ed00a58481ecf Mon Sep 17 00:00:00 2001
From: baldurk <baldurk@baldurk.org>
Date: Wed, 11 Jan 2017 14:49:12 +0000
Subject: [PATCH] Check top-level stride of buffers to know if we need to pad.
 Refs #485

---
 renderdoc/driver/gl/gl_shader_refl.cpp | 56 ++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/renderdoc/driver/gl/gl_shader_refl.cpp b/renderdoc/driver/gl/gl_shader_refl.cpp
index 15ccd6928..8c3403690 100644
--- a/renderdoc/driver/gl/gl_shader_refl.cpp
+++ b/renderdoc/driver/gl/gl_shader_refl.cpp
@@ -757,6 +757,13 @@ void ReconstructVarTree(const GLHookSet &gl, GLenum query, GLuint sepProg, GLuin
   else
     var.type.descriptor.elements = 0;
 
+  GLint topLevelStride = 0;
+  if(query == eGL_BUFFER_VARIABLE)
+  {
+    GLenum propName = eGL_TOP_LEVEL_ARRAY_STRIDE;
+    gl.glGetProgramResourceiv(sepProg, query, varIdx, 1, &propName, 1, NULL, &topLevelStride);
+  }
+
   vector<DynShaderConstant> *parentmembers = defaultBlock;
 
   if(values[3] != -1 && values[3] < numParentBlocks)
@@ -833,6 +840,7 @@ void ReconstructVarTree(const GLHookSet &gl, GLenum query, GLuint sepProg, GLuin
     parentVar.type.descriptor.rowMajorStorage = false;
     parentVar.type.descriptor.type = var.type.descriptor.type;
     parentVar.type.descriptor.elements = isarray ? RDCMAX(1U, uint32_t(arrayIdx + 1)) : 0;
+    parentVar.type.descriptor.arrayStride = topLevelStride;
 
     bool found = false;
 
@@ -1534,6 +1542,54 @@ void MakeShaderReflection(const GLHookSet &gl, GLenum shadType, GLuint sepProg,
     for(size_t ssbo = 0; ssbo < ssbos.size(); ssbo++)
     {
       sort(members[ssbo]);
+
+      // account for padding for std430 layout, if we have a root array of
+      // structs, we need to pad the struct up to have the correct alignment
+      if(members[ssbo].size() == 1 && !members[ssbo][0].type.members.empty() &&
+         members[ssbo][0].type.descriptor.arrayStride != 0)
+      {
+        // now that we're sorted, see what the tightly packed stride would be by looking at the last
+        // member
+        uint32_t desiredStride = members[ssbo][0].type.descriptor.arrayStride;
+
+        DynShaderConstant *last = &members[ssbo][0].type.members.back();
+        while(!last->type.members.empty())
+          last = &last->type.members.back();
+
+        // start from the offset
+        uint32_t stride = last->reg.vec * 16 + last->reg.comp * 4;
+
+        // add its size
+        uint32_t size = last->type.descriptor.rows * last->type.descriptor.cols * 4;
+        if(last->type.descriptor.type == eVar_Double)
+          size *= 2;
+
+        stride += size;
+
+        if(stride < desiredStride)
+        {
+          uint32_t padding = desiredStride - stride;
+
+          RDCASSERT((padding % 4) == 0 && padding <= 16, padding);
+
+          padding /= 4;
+
+          DynShaderConstant paddingVar;
+          paddingVar.name = "__padding";
+          paddingVar.reg.vec = last->reg.vec + (size / 16);
+          paddingVar.reg.comp = (last->reg.comp + size / 4) % 16;
+          paddingVar.type.descriptor.type = eVar_UInt;
+          paddingVar.type.descriptor.rows = 1;
+          paddingVar.type.descriptor.cols = padding;
+          paddingVar.type.descriptor.elements = 1;
+          paddingVar.type.descriptor.rowMajorStorage = false;
+          paddingVar.type.descriptor.arrayStride = 0;
+          paddingVar.type.descriptor.name = StringFormat::Fmt("uint%u", padding);
+
+          members[ssbo][0].type.members.push_back(paddingVar);
+        }
+      }
+
       copy(rwresources[ssbos[ssbo]].variableType.members, members[ssbo]);
     }