From d1ad5979392aa8bf00de4671a22dcd028d663a4b Mon Sep 17 00:00:00 2001
From: Gliniak <153369+Gliniak@users.noreply.github.com>
Date: Mon, 9 Mar 2026 21:52:00 +0100
Subject: [PATCH] [GPU] Vulkan: Fixed FSI render target path

AlphaToMask was causing crashes on linux due to missing SelectionMerge
---
 src/xenia/gpu/spirv_shader_translator_rb.cc | 22 ++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/src/xenia/gpu/spirv_shader_translator_rb.cc b/src/xenia/gpu/spirv_shader_translator_rb.cc
index 6a6cb9aa9..0d5e27fbd 100644
--- a/src/xenia/gpu/spirv_shader_translator_rb.cc
+++ b/src/xenia/gpu/spirv_shader_translator_rb.cc
@@ -3798,6 +3798,7 @@ void SpirvShaderTranslator::FSI_AlphaToMask() {
     spv::Block& block_msaa_4x = builder_->makeNewBlock();
     spv::Block& block_msaa_check_2x = builder_->makeNewBlock();
     spv::Block& block_msaa_merge = builder_->makeNewBlock();
+    spv::Block& block_msaa_merge_2x_1x = builder_->makeNewBlock();
 
     // Check if 4x MSAA
     spv::Id is_4x = builder_->createBinOp(
@@ -3826,6 +3827,8 @@ void SpirvShaderTranslator::FSI_AlphaToMask() {
     builder_->setBuildPoint(&block_msaa_check_2x);
     spv::Id is_2x = builder_->createBinOp(
         spv::OpIEqual, type_bool_, msaa_samples, builder_->makeUintConstant(1));
+    builder_->createSelectionMerge(&block_msaa_merge_2x_1x,
+                                   spv::SelectionControlDontFlattenMask);
     builder_->createConditionalBranch(is_2x, &block_msaa_2x_actual,
                                       &block_msaa_1x);
 
@@ -3836,13 +3839,24 @@ void SpirvShaderTranslator::FSI_AlphaToMask() {
                           coverage_2x);
     FSI_AlphaToMaskSample(false, 1, 1.0f, threshold_offset, 1.0f / 8.0f, alpha,
                           coverage_2x);
-    builder_->createBranch(&block_msaa_merge);
+    builder_->createBranch(&block_msaa_merge_2x_1x);
 
     // 1x MSAA path
     builder_->setBuildPoint(&block_msaa_1x);
     spv::Id coverage_1x = main_fsi_sample_mask_;
     FSI_AlphaToMaskSample(false, 0, 1.0f, threshold_offset, 1.0f / 4.0f, alpha,
                           coverage_1x);
+    builder_->createBranch(&block_msaa_merge_2x_1x);
+
+    // Merge 2x/1x MSAA paths
+    builder_->setBuildPoint(&block_msaa_merge_2x_1x);
+    id_vector_temp_.clear();
+    id_vector_temp_.push_back(coverage_2x);
+    id_vector_temp_.push_back(block_msaa_2x_actual.getId());
+    id_vector_temp_.push_back(coverage_1x);
+    id_vector_temp_.push_back(block_msaa_1x.getId());
+    spv::Id coverage_2x_1x =
+        builder_->createOp(spv::OpPhi, type_uint_, id_vector_temp_);
     builder_->createBranch(&block_msaa_merge);
 
     // Merge MSAA paths with PHI
@@ -3850,10 +3864,8 @@ void SpirvShaderTranslator::FSI_AlphaToMask() {
     id_vector_temp_.clear();
     id_vector_temp_.push_back(coverage_4x);
     id_vector_temp_.push_back(block_msaa_4x.getId());
-    id_vector_temp_.push_back(coverage_2x);
-    id_vector_temp_.push_back(block_msaa_2x_actual.getId());
-    id_vector_temp_.push_back(coverage_1x);
-    id_vector_temp_.push_back(block_msaa_1x.getId());
+    id_vector_temp_.push_back(coverage_2x_1x);
+    id_vector_temp_.push_back(block_msaa_merge_2x_1x.getId());
     spv::Id coverage_final =
         builder_->createOp(spv::OpPhi, type_uint_, id_vector_temp_);