- // Bitwise operators - logical and, logical or, logical xor, shift left,
- // shift right algebraic (shift in sign bits), shift right logical (shift in
- // zeroes), rotate left, rotate right, and byteswap.
- AND, OR, XOR, SHL, SRA, SRL, ROTL, ROTR, BSWAP,
+ /// Bitwise operators - logical and, logical or, logical xor.
+ AND, OR, XOR,
+
+ /// Shift and rotation operations. After legalization, the type of the
+ /// shift amount is known to be TLI.getShiftAmountTy(). Before legalization
+ /// the shift amount can be any type, but care must be taken to ensure it is
+ /// large enough. TLI.getShiftAmountTy() is i8 on some targets, but before
+ /// legalization, types like i1024 can occur and i8 doesn't have enough bits
+ /// to represent the shift amount. By convention, DAGCombine and
+ /// SelectionDAGBuilder forces these shift amounts to i32 for simplicity.
+ SHL, SRA, SRL, ROTL, ROTR,
+
+ /// Byte Swap and Counting operators.
+ BSWAP, CTTZ, CTLZ, CTPOP,