[clang] [llvm] Remove support for 3DNow!, both intrinsics and builtins. (PR #96246)

[Simon Pilgrim via cfe-commits]

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@@ -936,6 +936,24 @@ X86 Support
 ^^^^^^^^^^^
 
 - Remove knl/knm specific ISA supports: AVX512PF, AVX512ER, PREFETCHWT1
+- Support has been removed for the AMD "3DNow!" instruction-set.
+  Neither modern AMD CPUs, nor any Intel CPUs implement these
+  instructions, and they were never widely used.
+
+  * The options ``-m3dnow`` and ``-m3dnowa`` are no longer honored, and will emit a warning if used.
+  * The macros ``__3dNOW__`` and ``__3dNOW_A__`` are no longer ever set by the compiler.
+  * The header ``<mm3dnow.h>`` is deprecated, and emits a warning if included.
+  * The 3dNow intrinsic functions have been removed: ``_m_femms``,
+    ``_m_pavgusb``, ``_m_pf2id``, ``_m_pfacc``, ``_m_pfadd``,
+    ``_m_pfcmpeq``, ``_m_pfcmpge``, ``_m_pfcmpgt``, ``_m_pfmax``,
+    ``_m_pfmin``, ``_m_pfmul``, ``_m_pfrcp``, ``_m_pfrcpit1``,
+    ``_m_pfrcpit2``, ``_m_pfrsqrt``, ``_m_pfrsqrtit1``, ``_m_pfsub``,
+    ``_m_pfsubr``, ``_m_pi2fd``, ``_m_pmulhrw``, ``_m_pf2iw``,
+    ``_m_pfnacc``, ``_m_pfpnacc``, ``_m_pi2fw``, ``_m_pswapdsf``,
+    ``_m_pswapdsi``.
+  * The compiler builtins corresponding to each of the above
+    intrinsics have also been removed  (``__builtin_ia32_femms``, and so on).
----------------
RKSimon wrote:

Please can you make it clear that inline-asm is still supported

https://github.com/llvm/llvm-project/pull/96246