[InstCombine] Remove mul of SPF abs fold

Remove the fold working on abs in SPF representation now that we
canonicalize SPF to intrinsics.

This is not strictly NFC because the SPF fold might fire for
non-canonical IR due to multi-use, but given the lack of test
coverage, I assume this is not important.

Author: nikic

llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp

@@ -319,19 +319,12 @@ Instruction *InstCombinerImpl::visitMul(BinaryOperator &I) {
   }
 
   // abs(X) * abs(X) -> X * X
-  // nabs(X) * nabs(X) -> X * X
-  if (Op0 == Op1) {
-    Value *X, *Y;
-    SelectPatternFlavor SPF = matchSelectPattern(Op0, X, Y).Flavor;
-    if (SPF == SPF_ABS || SPF == SPF_NABS)
-      return BinaryOperator::CreateMul(X, X);
-
-    if (match(Op0, m_Intrinsic<Intrinsic::abs>(m_Value(X))))
-      return BinaryOperator::CreateMul(X, X);
-  }
+  Value *X;
+  if (Op0 == Op1 && match(Op0, m_Intrinsic<Intrinsic::abs>(m_Value(X))))
+    return BinaryOperator::CreateMul(X, X);
 
   {
-    Value *X, *Y;
+    Value *Y;
     // abs(X) * abs(Y) -> abs(X * Y)
     if (I.hasNoSignedWrap() &&
         match(Op0,
@@ -344,7 +337,7 @@ Instruction *InstCombinerImpl::visitMul(BinaryOperator &I) {
   }
 
   // -X * C --> X * -C
-  Value *X, *Y;
+  Value *Y;
   Constant *Op1C;
   if (match(Op0, m_Neg(m_Value(X))) && match(Op1, m_Constant(Op1C)))
     return BinaryOperator::CreateMul(X, ConstantExpr::getNeg(Op1C));