[llvm] [InstCombine] Simplifiy `(-x * y * -x)` into `(x * y * x)` (PR #72953)

[via llvm-commits]

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@@ -352,6 +352,19 @@ Instruction *InstCombinerImpl::visitMul(BinaryOperator &I) {
   if (match(&I, m_c_Mul(m_OneUse(m_Neg(m_Value(X))), m_Value(Y))))
     return BinaryOperator::CreateNeg(Builder.CreateMul(X, Y));
 
+  // -X * Y * -X --> X * Y * X
+  if (match(&I, m_c_Mul(m_Neg(m_Value(X)),
+                        m_c_Mul(m_Value(Y), m_Neg(m_Deferred(X)))))) {
+    if (X == Y) {
+      Value *MulXY = Builder.CreateMul(X, Y);
+      bool BO0HasNSW = cast<OverflowingBinaryOperator>(Op0)->hasNoSignedWrap();
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goldsteinn wrote:

Think this only works if its the `mul` that has `nsw`. `Op0` is not guranteed to be the `mul` (b.c you do commutative match above).

https://github.com/llvm/llvm-project/pull/72953