[InstCombine] Support or disjoint in displaced shift fold

When I originally added this fold, it did not actually fix my
motivation case, where the add was represented as an or. Now that
we have the disjoint flag this can finally be cleanly supported.

Author: nikic

llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp

@@ -2127,10 +2127,10 @@ Instruction *InstCombinerImpl::foldBinOpOfDisplacedShifts(BinaryOperator &I) {
   Constant *ShiftedC1, *ShiftedC2, *AddC;
   Type *Ty = I.getType();
   unsigned BitWidth = Ty->getScalarSizeInBits();
-  if (!match(&I,
-             m_c_BinOp(m_Shift(m_ImmConstant(ShiftedC1), m_Value(ShAmt)),
-                       m_Shift(m_ImmConstant(ShiftedC2),
-                               m_Add(m_Deferred(ShAmt), m_ImmConstant(AddC))))))
+  if (!match(&I, m_c_BinOp(m_Shift(m_ImmConstant(ShiftedC1), m_Value(ShAmt)),
+                           m_Shift(m_ImmConstant(ShiftedC2),
+                                   m_AddLike(m_Deferred(ShAmt),
+                                             m_ImmConstant(AddC))))))
     return nullptr;
 
   // Make sure the add constant is a valid shift amount.

llvm/test/Transforms/InstCombine/binop-of-displaced-shifts.ll

@@ -332,10 +332,7 @@ define <2 x i8> @shl_or_non_splat_out_of_range(<2 x i8> %x) {
 define i8 @shl_or_with_or_disjoint_instead_of_add(i8 %x) {
 ; CHECK-LABEL: define i8 @shl_or_with_or_disjoint_instead_of_add
 ; CHECK-SAME: (i8 [[X:%.*]]) {
-; CHECK-NEXT:    [[SHIFT:%.*]] = shl i8 16, [[X]]
-; CHECK-NEXT:    [[ADD:%.*]] = or disjoint i8 [[X]], 1
-; CHECK-NEXT:    [[SHIFT2:%.*]] = shl i8 3, [[ADD]]
-; CHECK-NEXT:    [[BINOP:%.*]] = or i8 [[SHIFT]], [[SHIFT2]]
+; CHECK-NEXT:    [[BINOP:%.*]] = shl i8 22, [[X]]
 ; CHECK-NEXT:    ret i8 [[BINOP]]
 ;
   %shift = shl i8 16, %x