spirv-opt: add pass to Spread Volatile semantics (#4667)

Add a pass to spread Volatile semantics to variables with SMIDNV,
WarpIDNV, SubgroupSize, SubgroupLocalInvocationId, SubgroupEqMask,
SubgroupGeMask, SubgroupGtMask, SubgroupLeMask, or SubgroupLtMask BuiltIn
decorations or OpLoad for them when the shader model is the ray
generation, closest hit, miss, intersection, or callable shaders. This
pass can be used for VUID-StandaloneSpirv-VulkanMemoryModel-04678 and
VUID-StandaloneSpirv-VulkanMemoryModel-04679 (See "Standalone SPIR-V
Validation" section of Vulkan spec "Appendix A: Vulkan Environment for
SPIR-V").

Handle variables used by multiple entry points:

1. Update error check to make it working regardless of the order of
   entry points.
2. For a variable, if it is used by two entry points E1 and E2 and
   it needs the Volatile semantics for E1 while it does not for E2
  - If VulkanMemoryModel capability is enabled, which means we have to
    set memory operation of load instructions for the variable, we
    update load instructions in E1, but do not update the ones in E2.
  - If VulkanMemoryModel capability is disabled, which means we have
    to add Volatile decoration for the variable, we report an error
    because E1 needs to add Volatile decoration for the variable while
    E2 does not.

For the simplicity of the implementation, we assume that all functions
other than entry point functions are inlined.

1 files changed, 13 insertions, 0 deletions

diff --git a/include/spirv-tools/optimizer.hpp b/include/spirv-tools/optimizer.hpp
index 5d173c111..3e63037c5 100644
--- a/include/spirv-tools/optimizer.hpp
+++ b/include/spirv-tools/optimizer.hpp
@@ -835,6 +835,19 @@ Optimizer::PassToken CreateFixStorageClassPass();
 //   inclusive.
 Optimizer::PassToken CreateGraphicsRobustAccessPass();
 
+// Create a pass to spread Volatile semantics to variables with SMIDNV,
+// WarpIDNV, SubgroupSize, SubgroupLocalInvocationId, SubgroupEqMask,
+// SubgroupGeMask, SubgroupGtMask, SubgroupLeMask, or SubgroupLtMask BuiltIn
+// decorations or OpLoad for them when the shader model is the ray generation,
+// closest hit, miss, intersection, or callable. This pass can be used for
+// VUID-StandaloneSpirv-VulkanMemoryModel-04678 and
+// VUID-StandaloneSpirv-VulkanMemoryModel-04679 (See "Standalone SPIR-V
+// Validation" section of Vulkan spec "Appendix A: Vulkan Environment for
+// SPIR-V"). When the SPIR-V version is 1.6 or above, the pass also spreads
+// the Volatile semantics to a variable with HelperInvocation BuiltIn decoration
+// in the fragement shader.
+Optimizer::PassToken CreateSpreadVolatileSemanticsPass();
+
 // Create a pass to replace a descriptor access using variable index.
 // This pass replaces every access using a variable index to array variable
 // |desc| that has a DescriptorSet and Binding decorations with a constant