fix(shader): keep pixel invocations running after a BDA fault in a program that reads lanes by index

core/libs/prx/libSceAgcDriver/tests/BdaContracts.cpp

@@ -177,6 +177,26 @@ void RunBdaContractTests() {
     program.BlockOrder().push_back(&block);
     ValidateBdaTarget(program, target);
     AgcDriver::Graphics::Require(!BdaInvocationsMayStop(program), "a BDA program with barriers must keep its invocations running");
+    for (const auto opcode : {IrOpcode::ReadLane, IrOpcode::WriteLane}) {
+        IrProgram lanes;
+        lanes.Resources().stage = IrShaderStage::Pixel;
+        auto& laneBlock = lanes.CreateBlock();
+        laneBlock.AppendInstruction(&lanes.CreateValue(opcode, IrType::U32));
+        lanes.BlockOrder().push_back(&laneBlock);
+        AgcDriver::Graphics::Require(!BdaInvocationsMayStop(lanes), std::string("a pixel program with ") + (opcode == IrOpcode::ReadLane ? "v_readlane" : "v_writelane") + " must keep its invocations running: a waterfall over a mask that holds a stopped lane never clears its bit");
+    }
+    IrProgram plain;
+    plain.Resources().stage = IrShaderStage::Pixel;
+    auto& plainBlock = plain.CreateBlock();
+    plainBlock.AppendInstruction(&plain.CreateValue(IrOpcode::ReadFirstLane, IrType::U32));
+    plain.BlockOrder().push_back(&plainBlock);
+    AgcDriver::Graphics::Require(BdaInvocationsMayStop(plain), "a BDA program with only v_readfirstlane must still stop a faulting invocation");
+    IrProgram computeLanes;
+    computeLanes.Resources().stage = IrShaderStage::Compute;
+    auto& computeBlock = computeLanes.CreateBlock();
+    computeBlock.AppendInstruction(&computeLanes.CreateValue(IrOpcode::ReadLane, IrType::U32));
+    computeLanes.BlockOrder().push_back(&computeBlock);
+    AgcDriver::Graphics::Require(BdaInvocationsMayStop(computeLanes), "a compute program with v_readlane and no barrier must still stop a faulting invocation");
     program.Resources().stage = IrShaderStage::TessellationControl;
     ValidateBdaTarget(program, target);
     program.Resources().stage = IrShaderStage::Compute;

core/shader/recompiler/SpirvBackend/src/SpirvBdaRead.cpp

@@ -414,9 +414,12 @@ void ValidateBdaTarget(const IrProgram& program, const SpirvTargetOptions& targe
 }
 
 bool BdaInvocationsMayStop(const IrProgram& program) {
+    const bool pixel = program.Resources().stage == IrShaderStage::Pixel;
     for (const auto* block : program.BlockOrder()) {
         for (const auto* instruction : block->Instructions()) {
-            if (instruction->Opcode() == IrOpcode::Barrier) return false;
+            const auto opcode = instruction->Opcode();
+            if (opcode == IrOpcode::Barrier) return false;
+            if (pixel && (opcode == IrOpcode::ReadLane || opcode == IrOpcode::WriteLane)) return false;
         }
     }
     return true;