[llvm] [ValueTracking] Handle not cond to assume. (PR #127140)

[Yingwei Zheng via llvm-commits]

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@@ -441,16 +441,28 @@ void llvm::computeKnownBitsFromRangeMetadata(const MDNode &Ranges,
 }
 
 static bool isEphemeralValueOf(const Instruction *I, const Value *E) {
-  SmallVector<const Value *, 16> WorkSet(1, I);
-  SmallPtrSet<const Value *, 32> Visited;
-  SmallPtrSet<const Value *, 16> EphValues;
 
   // The instruction defining an assumption's condition itself is always
   // considered ephemeral to that assumption (even if it has other
   // non-ephemeral users). See r246696's test case for an example.
   if (is_contained(I->operands(), E))
     return true;
 
+  SmallPtrSet<const Value *, 32> Visited{I};
+  SmallPtrSet<const Value *, 16> EphValues{I};
+
+  Value *X;
+  if (match(I, m_Intrinsic<Intrinsic::assume>(m_Not(m_Value(X))))) {
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dtcxzyw wrote:

I am ok with the IR diff. But I am a bit confused by this line. Do we really need to specially handle `assume(not(cond))`?

That is, we should also match trunc here if we want to remove `!IsAssume &&` from the following code:
https://github.com/llvm/llvm-project/blob/70b95ca6dbee7036dcfa5995ff804471fd7e8c2a/llvm/lib/Analysis/ValueTracking.cpp#L10346


https://github.com/llvm/llvm-project/pull/127140