From 79e80c83379020970afaaa3268c6db1b1de78563 Mon Sep 17 00:00:00 2001
From: Jake Turner <jake@evansturner.co.uk>
Date: Mon, 28 Apr 2025 11:28:14 +0100
Subject: [PATCH] Added assert for Op::ControlBarrier that the workgroup is
 converged

New helper method ThreadState::WorkgroupIsDiverged()
---
 .../driver/shaders/spirv/spirv_debug.cpp      | 27 ++++++++++++++++++-
 renderdoc/driver/shaders/spirv/spirv_debug.h  |  3 +++
 .../shaders/spirv/spirv_debug_setup.cpp       |  5 ++++
 3 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/renderdoc/driver/shaders/spirv/spirv_debug.cpp b/renderdoc/driver/shaders/spirv/spirv_debug.cpp
index 766a83522..ae35222a1 100644
--- a/renderdoc/driver/shaders/spirv/spirv_debug.cpp
+++ b/renderdoc/driver/shaders/spirv/spirv_debug.cpp
@@ -739,6 +739,26 @@ void ThreadState::EnterEntryPoint(ShaderDebugState *state)
   EnterFunction({});
 
   m_State = NULL;
+  currentInstruction = nextInstruction;
+}
+
+bool ThreadState::WorkgroupIsDiverged(const rdcarray<ThreadState> &workgroup)
+{
+  uint32_t instr0 = ~0U;
+  for(size_t i = 0; i < workgroup.size(); i++)
+  {
+    if(workgroup[i].Finished())
+      continue;
+    if(instr0 == ~0U)
+    {
+      instr0 = workgroup[i].currentInstruction;
+      continue;
+    }
+    // not executing the same instruction
+    if(workgroup[i].currentInstruction != instr0)
+      return true;
+  }
+  return false;
 }
 
 void ThreadState::StepNext(ShaderDebugState *state, const rdcarray<ThreadState> &workgroup,
@@ -3741,11 +3761,16 @@ void ThreadState::StepNext(ShaderDebugState *state, const rdcarray<ThreadState>
       //////////////////////////////////////////////////////////////////////////////
 
     case Op::MemoryBarrier:
-    case Op::ControlBarrier:
     {
       // do nothing for now
       break;
     }
+    case Op::ControlBarrier:
+    {
+      // For thread barriers the threads must be converged
+      RDCASSERT(!WorkgroupIsDiverged(workgroup));
+      break;
+    }
     case Op::Label:
     case Op::SelectionMerge:
     case Op::LoopMerge:
diff --git a/renderdoc/driver/shaders/spirv/spirv_debug.h b/renderdoc/driver/shaders/spirv/spirv_debug.h
index d52a2543f..bbb45ab5f 100644
--- a/renderdoc/driver/shaders/spirv/spirv_debug.h
+++ b/renderdoc/driver/shaders/spirv/spirv_debug.h
@@ -202,6 +202,7 @@ struct ThreadState
 
   bool Finished() const;
 
+  uint32_t currentInstruction;
   uint32_t nextInstruction;
 
   const GlobalState &global;
@@ -269,6 +270,8 @@ private:
   void SkipIgnoredInstructions();
   void SetConvergencePoint(Id block);
 
+  static bool WorkgroupIsDiverged(const rdcarray<ThreadState> &workgroup);
+
   ShaderDebugState *m_State = NULL;
 };
 
diff --git a/renderdoc/driver/shaders/spirv/spirv_debug_setup.cpp b/renderdoc/driver/shaders/spirv/spirv_debug_setup.cpp
index 3c5a83595..ddeb0b74c 100644
--- a/renderdoc/driver/shaders/spirv/spirv_debug_setup.cpp
+++ b/renderdoc/driver/shaders/spirv/spirv_debug_setup.cpp
@@ -2728,6 +2728,11 @@ rdcarray<ShaderDebugState> Debugger::ContinueDebug()
         if(thread.diverged)
           ++countDivergedThreads;
       }
+      for(size_t lane = 0; lane < workgroup.size(); lane++)
+      {
+        if(activeMask[lane])
+          workgroup[lane].currentInstruction = workgroup[lane].nextInstruction;
+      }
       if(countConvergePointThreads)
       {
         // all the active threads should have a convergence point if any have one