[clang] [llvm] [X86][MC,Driver] Support -msse2avx to encode SSE instruction with VEX prefix (PR #96860)

[Shengchen Kan via cfe-commits]

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@@ -2711,6 +2711,8 @@ static void CollectArgsForIntegratedAssembler(Compilation &C,
   }
   if (!UseRelaxRelocations)
     CmdArgs.push_back("-mrelax-relocations=no");
+  if (Args.hasArg(options::OPT_msse2avx))
+    CmdArgs.push_back("-msse2avx");
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KanRobert wrote:

To address @MaskRay target specific comment. Probably you need to put it under sth like `case llvm::Triple::x86 : case llvm::Triple::x86_64:`

https://github.com/llvm/llvm-project/pull/96860