[clang] [X86][Clang] Support constexpr evaluation of cvtpd2ps intrinsics (PR #169980)

[Simon Pilgrim via cfe-commits]

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+// RUN: %clang_cc1 -std=c++20 -triple x86_64-unknown-unknown -target-feature +avx -target-feature +avx512f -target-feature +avx512vl -verify %s
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RKSimon wrote:

Add -fexperimental-new-constant-interpreter test coverage as well

https://github.com/llvm/llvm-project/pull/169980