[llvm] [InstCombine] Fold -X / -Y -> X / Y (PR #88422)

[via llvm-commits]

================
@@ -1581,12 +1581,30 @@ Instruction *InstCombinerImpl::visitSDiv(BinaryOperator &I) {
     }
   }
 
-  // -X / Y --> -(X / Y)
   Value *Y;
+  // -X / -Y --> (X / Y)
+  if (match(&I, m_SDiv(m_NSWSub(m_Zero(), m_Value(X)),
+                       m_NSWSub(m_Zero(), m_Value(Y))))) {
+    auto *NewDiv = BinaryOperator::CreateSDiv(X, Y);
+    NewDiv->setIsExact(I.isExact());
+    return NewDiv;
+  }
+
+  // -X / Y --> -(X / Y)
   if (match(&I, m_SDiv(m_OneUse(m_NSWSub(m_Zero(), m_Value(X))), m_Value(Y))))
     return BinaryOperator::CreateNSWNeg(
         Builder.CreateSDiv(X, Y, I.getName(), I.isExact()));
 
+  // X / -Y --> -(X / Y), if X is known to not be INT_MIN
+  KnownBits KnownDividend = computeKnownBits(Op0, 0, &I);
+  if (!KnownDividend.getMinValue().isMinSignedValue() &&
----------------
goldsteinn wrote:

getSignedMinValue()

https://github.com/llvm/llvm-project/pull/88422