[llvm] [Mips] ISel zext nneg the same as sext for Mips64. (PR #102852)

[Matt Arsenault via llvm-commits]

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@@ -837,13 +837,20 @@ def : MipsPat<(MipsExt (i32 (trunc GPR64:$src)), immZExt5:$pos, immZExt5:$size),
               (EXTRACT_SUBREG (DEXT GPR64:$src, immZExt5:$pos, immZExt5:$size), sub_32)>,
               ISA_MIPS3, GPR_64;
 
+def zext_nneg : PatFrag<(ops node:$src), (zext node:$src), [{
+  return N->getFlags().hasNonNeg();
+}]>;
+def sext_like : PatFrags<(ops node:$src),
+                         [(zext_nneg node:$src),
+                          (sext node:$src)]>;
+
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arsenm wrote:

These probably should go in the general TargetSelectionDAG.td 

https://github.com/llvm/llvm-project/pull/102852