Support coherent/globallycoherent in DescriptorHandle type modifier

[nv-slang-bot]

Summary

• Adds CoherentModifierVal to the type modifier system so DescriptorHandle<coherent T> and DescriptorHandle<globallycoherent T> compile instead of triggering ICE E99999
• Threads the coherent attribute through the full pipeline: AST → IR → HLSL/GLSL/SPIRV emit
• Adds regression test tests/bugs/gh-10852.slang

Fixes #10852

Changes

• AST: New CoherentModifierVal class + ASTBuilder::getCoherentModifierVal() factory
• Semantic check: Handle GloballyCoherentModifier in checkTypeModifier() (was the ICE source)
• IR: New CoherentAttr attribute in slang-ir-insts.lua + stable name
• IR lowering: visitCoherentModifierVal → kIROp_CoherentAttr
• HLSL emit: CoherentAttr → globallycoherent prefix
• GLSL emit: CoherentAttr → coherent prefix
• SPIRV emit: CoherentAttr → OpDecorate Coherent + coherent memory operands for Vulkan memory model; unwrap IRAttributedType in descriptor handle cast

Test

Added tests/bugs/gh-10852.slang — verifies HLSL output includes globallycoherent RWTexture2D<float4> for both coherent and globallycoherent descriptor handles.

Labels

pr: non-breaking

[slangbot]

⚠️ IR Instruction Files Changed

This PR modifies IR instruction definition files. Please review if you need to update the following constants in source/slang/slang-ir.h:

• k_minSupportedModuleVersion: Should be incremented if you're removing instructions or making breaking changes
• k_maxSupportedModuleVersion: Should be incremented when adding new instructions

These version numbers help ensure compatibility between different versions of compiled modules.