[llvm] [SPIR-V] Add capability for non-uniform indexing for `StructuredBuffer` types. (PR #163424)

[Nathan Gauër via llvm-commits]

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@@ -3,6 +3,7 @@
 
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Keenuts wrote:

If I'm not mistaken it's not exactly that:
 - the extension became "core" in 1.5, meaning the SPV_EXT_descriptor_indexing extensions is not required in the SPIR-V Module to use the capability starting SPV1.5.
 - before SPV 1.5, if you want to use the capability, you need to also declare the extension in the module.
What the extension requires is SPV 1.0 as minimum.(`This extension requires SPIR-V 1.0.)`, and to correctly read the extensions rules when it says "modify" or such, you need to consider comparing it against SPV 1.3 spec (`This extension is written against the SPIR-V Specification, Version 1.3 Revision 1.`)

https://github.com/llvm/llvm-project/pull/163424