[clang] [llvm] [mlir] Remove the `x86_mmx` IR type. (PR #98505)

[James Y Knight via cfe-commits]

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@@ -57594,6 +57599,86 @@ static SDValue combinePDEP(SDNode *N, SelectionDAG &DAG,
   return SDValue();
 }
 
+// Fixup the MMX intrinsics' types: in IR they are expressed with <1 x i64>,
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jyknight wrote:

We perhaps _could_ use i64, but i64 is also not a legal type on 32bit x86, so I don't think that would actually help here.

I chose <1 x i64> mainly because that's what Clang was already using for MMX values.

https://github.com/llvm/llvm-project/pull/98505