[llvm] [InstSimplify] Simplify select if it combinated `and/or/xor` (PR #73362)

[via llvm-commits]

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@@ -4585,6 +4585,50 @@ static Value *simplifySelectWithFakeICmpEq(Value *CmpLHS, Value *CmpRHS,
                                Pred == ICmpInst::ICMP_EQ);
 }
 
+/// Try to simplify the Select instruction consisting of and/or/xor.
+static Value *simplifySelectWithAndOrXorBitOp(Value *CmpLHS, Value *CmpRHS,
+                                              Value *TrueVal, Value *FalseVal) {
+  Value *X, *Y;
+  // (X & Y) == 0 ? X | Y : X ^ Y   --> X ^ Y
+  // (X & Y) == 0 ? X ^ Y : X | Y   --> X | Y
+  if (match(CmpLHS, m_And(m_Value(X), m_Value(Y))) && match(CmpRHS, m_Zero())) {
+    if ((match(TrueVal, m_c_Or(m_Specific(X), m_Specific(Y))) &&
+         match(FalseVal, m_c_Xor(m_Specific(X), m_Specific(Y)))) ||
+        (match(FalseVal, m_c_Or(m_Specific(X), m_Specific(Y))) &&
+         match(TrueVal, m_c_Xor(m_Specific(X), m_Specific(Y)))))
+      return FalseVal;
+  }
+  // (X | Y) == 0 ? X & Y : X ^ Y   --> X ^ Y
+  // (X | Y) == 0 ? X ^ Y : X & Y   --> X & Y
+  if (match(CmpLHS, m_Or(m_Value(X), m_Value(Y))) && match(CmpRHS, m_Zero())) {
+    if ((match(TrueVal, m_c_And(m_Specific(X), m_Specific(Y))) &&
+         match(FalseVal, m_c_Xor(m_Specific(X), m_Specific(Y)))) ||
+        (match(FalseVal, m_c_And(m_Specific(X), m_Specific(Y))) &&
+         match(TrueVal, m_c_Xor(m_Specific(X), m_Specific(Y)))))
+      return FalseVal;
+  }
+  // (X ^ Y) == 0 ? X | Y : X & Y   --> X & Y
+  // (X ^ Y) == 0 ? X & Y : X | Y   --> X | Y
+  if (match(CmpLHS, m_Xor(m_Value(X), m_Value(Y))) && match(CmpRHS, m_Zero())) {
----------------
goldsteinn wrote:

What you could also do to minimize the code duplication is do the following:

```
if ((match(CmpLHS, m_Xor(m_Value(X), m_Value(Y))) && match(CmpRHS, m_Zero())) || (match(CmpLHS, m_Value(X)) && match(CmpRhs, m_Value(Y)))) {
```

Then drop the lines below.

@nikic, is there a general policy for whether we can rely on `InstCombine` canonicalizations in `InstSimplify`?

https://github.com/llvm/llvm-project/pull/73362