[clang] [HLSL] Add IsMultiSampled HLSL resource attribute (PR #211125)

[Aaron Ballman via cfe-commits]

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+// RUN: %clang_cc1 -triple dxil-pc-shadermodel6.0-library -x hlsl -o - %s -verify
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AaronBallman wrote:

Thanks! Yeah, moving them all at once would be reasonable.

https://github.com/llvm/llvm-project/pull/211125