ShaderCompiler: preserve original sampler names colliding with HLSL/MSL keywords

[bkaradzic-microsoft]

Problem

SPIRV-Cross's HLSL and MSL backends rename any shader resource whose name collides with a reserved keyword of the target language, prepending an underscore. Babylon.js generates GLSL samplers named Texture2D and Texture2DArray, which are HLSL built-in object types, so they are emitted into the bgfx uniform table as _Texture2D / _Texture2DArray.

Both bgfx and Babylon.js look samplers up by their original GLSL name, so the renamed uniform never binds. There is no error — the stage just silently samples nothing and renders transparent.

Fix

AppendSamplers recovers the pre-transpile name from the parser's ParsedIR via get_name(id). The Compiler transpiles a private copy of the IR, so the parser still holds the original names. That name is emitted into the bgfx uniform table and the stage map.

• The texture register (DecorationBinding) is untouched — only the app-facing name changes.
• Non-colliding samplers resolve to the identical string, so they are bit-for-bit unaffected.
• The existing OpenGL stage-assignment guard is now keyed on the recovered name so the vertex and fragment passes agree on the same identifier.

Validation

Built x64 / Release / D3D11 against this branch and ran the full Playground validation suite:

Run complete. ran=300 passed=300 failed=0 missingRef=0 skipped=420

No regressions. Because every non-colliding sampler keeps its current name, the change is a no-op for all 300 currently-enabled tests.

Scope

This is intentionally code-only — no config.json changes. The test this unblocks (MultiRenderTarget with different texture types, #XSNYAU#22) also needs a matching Babylon.js-side fix for the mixed-type MRT write path, so its un-exclusion is deliberately left for a later change once both halves are in. Verified: with only this fix applied, that test still fails, so enabling it here would red the build.

[Copilot]

Pull request overview

This PR fixes sampler/uniform binding failures caused by SPIRV-Cross renaming GLSL sampler identifiers that collide with HLSL/MSL reserved keywords (e.g., Texture2D → _Texture2D). It does so by emitting the original (pre-transpile) resource name into the bgfx uniform table and by using that same recovered name when maintaining the shared stage-to-texture-unit map.

Changes:

• Extend AppendSamplers to accept the parser’s original spirv_cross::ParsedIR and recover the pre-transpile sampler name via originalIr.get_name(sampler.id).
• Emit recovered sampler names into the bgfx shader binary uniform table (falling back to sampler.name when unavailable).
• Key the OpenGL stage-assignment guard and stage map entries on the recovered name so vertex/fragment passes agree on the identifier.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
Plugins/ShaderCompiler/Source/ShaderCompilerCommon.h	Updates AppendSamplers signature to accept the original ParsedIR for name recovery.
Plugins/ShaderCompiler/Source/ShaderCompilerCommon.cpp	Recovers original sampler names from ParsedIR, writes them to the uniform table, and keys stage mapping consistently on the recovered name.