[llvm] [ValueTracking] Handle trunc to i1 as condition in dominating condition. (PR #126414)

[Andreas Jonson via llvm-commits]

================
@@ -801,6 +801,22 @@ static void computeKnownBitsFromCond(const Value *V, Value *Cond,
 
   if (auto *Cmp = dyn_cast<ICmpInst>(Cond))
     computeKnownBitsFromICmpCond(V, Cmp, Known, SQ, Invert);
+
+  if (match(Cond, m_Not(m_Value(Cond))))
+    Invert = !Invert;
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andjo403 wrote:

notice at least some regressions in opt-benchmark when I removed it,
one example I think is this pattern: 
```
  %630 = trunc i8 %629 to i1
  %not. = xor i1 %630, true
  %.0215.shrunk. = or i1 %spec.select472, %not.
  br i1 %.0215.shrunk., label %632, label %.thread
```

so I shall maybe try to make a test that cover this case?

https://github.com/llvm/llvm-project/pull/126414