[llvm] [InstCombine] Enable select freeze poison folding when storing value (PR #129776)

[Yingwei Zheng via llvm-commits]

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@@ -4842,8 +4847,11 @@ Instruction *InstCombinerImpl::visitFreeze(FreezeInst &I) {
 
   Constant *C;
   if (match(Op0, m_Constant(C)) && C->containsUndefOrPoisonElement()) {
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dtcxzyw wrote:

BTW, as it is not suitable to handle this fold under `getUndefReplacement`, can we move the logic into `InstCombinerImpl::visitSelect`?
```
Instruction *InstCombinerImpl::visitSelectInst(SelectInst &SI) {
...
    if (match(TrueVal, m_Freeze(m_Poison())) &&
        isGuaranteedNotToBeUndefOrPoison(FalseVal, &AC, &I, &DT))
      return replaceInstUsesWith(FalseVal);
    if (match(FalseVal, m_Freeze(m_Poison())) &&
        isGuaranteedNotToBeUndefOrPoison(TrueVal, &AC, &I, &DT))
      return replaceInstUsesWith(TrueVal);
```


https://github.com/llvm/llvm-project/pull/129776