[llvm] [InstCombine] Improve select equiv fold for plain condition (PR #83405)

[via llvm-commits]

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@@ -500,6 +500,44 @@ static bool isSelect01(const APInt &C1I, const APInt &C2I) {
   return C1I.isOne() || C1I.isAllOnes() || C2I.isOne() || C2I.isAllOnes();
 }
 
+/// Try to simplify a select instruction when the user of its select user
+/// indicates the condition.
+static bool simplifySeqSelectWithSameCond(SelectInst &SI,
+                                          const SimplifyQuery &SQ,
+                                          InstCombinerImpl &IC) {
+  Value *CondVal = SI.getCondition();
+  if (match(CondVal, m_ImmConstant()))
+    return false;
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vfdff wrote:

Yes, it isn't.
[#85663](https://github.com/llvm/llvm-project/pull/85663) is a more general improvement by nikic, and it has some compile time regression, so I continue on this solution.

https://github.com/llvm/llvm-project/pull/83405