llvm/include/llvm/Target/GlobalISel/Combine.td

//===- Combine.td - Combine rule definitions ---------------*- tablegen -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// Declare GlobalISel combine rules and provide mechanisms to opt-out.
//
//===----------------------------------------------------------------------===//

// Common base class for GICombineRule and GICombineGroup.
class GICombine {
  // See GICombineGroup. We only declare it here to make the tablegen pass
  // simpler.
  list<GICombine> Rules = ?;
}

// A group of combine rules that can be added to a GICombiner or another group.
class GICombineGroup<list<GICombine> rules> : GICombine {
  // The rules contained in this group. The rules in a group are flattened into
  // a single list and sorted into whatever order is most efficient. However,
  // they will never be re-ordered such that behaviour differs from the
  // specified order. It is therefore possible to use the order of rules in this
  // list to describe priorities.
  let Rules = rules;
}

class GICombinerHelperArg<string type, string name> {
  string Type = type;
  string Name = name;
}

// Declares a combiner helper class
class GICombinerHelper<string classname, list<GICombine> rules>
    : GICombineGroup<rules> {
  // The class name to use in the generated output.
  string Classname = classname;
  // The name of a run-time compiler option that will be generated to disable
  // specific rules within this combiner.
  string DisableRuleOption = ?;
  // The state class to inherit from (if any). The generated helper will inherit
  // from this class and will forward arguments to its constructors.
  string StateClass = "";
  // Any additional arguments that should be appended to the tryCombine*().
  list<GICombinerHelperArg> AdditionalArguments =
      [GICombinerHelperArg<"CombinerHelper &", "Helper">];
}
class GICombineRule<dag defs, dag match, dag apply> : GICombine {
  /// Defines the external interface of the match rule. This includes:
  /// * The names of the root nodes (requires at least one)
  /// See GIDefKind for details.
  dag Defs = defs;

  /// Defines the things which must be true for the pattern to match
  /// See GIMatchKind for details.
  dag Match = match;

  /// Defines the things which happen after the decision is made to apply a
  /// combine rule.
  /// See GIApplyKind for details.
  dag Apply = apply;
}

/// The operator at the root of a GICombineRule.Defs dag.
def defs;

/// All arguments of the defs operator must be subclasses of GIDefKind or
/// sub-dags whose operator is GIDefKindWithArgs.
class GIDefKind;
class GIDefKindWithArgs;
/// Declare a root node. There must be at least one of these in every combine
/// rule.
/// TODO: The plan is to elide `root` definitions and determine it from the DAG
///       itself with an overide for situations where the usual determination
///       is incorrect.
def root : GIDefKind;

/// Declares data that is passed from the match stage to the apply stage.
class GIDefMatchData<string type> : GIDefKind {
  /// A C++ type name indicating the storage type.
  string Type = type;
}

def extending_load_matchdata : GIDefMatchData<"PreferredTuple">;
def indexed_load_store_matchdata : GIDefMatchData<"IndexedLoadStoreMatchInfo">;
def instruction_steps_matchdata: GIDefMatchData<"InstructionStepsMatchInfo">;

/// The operator at the root of a GICombineRule.Match dag.
def match;
/// All arguments of the match operator must be either:
/// * A subclass of GIMatchKind
/// * A subclass of GIMatchKindWithArgs
/// * A subclass of Instruction
/// * A MIR code block (deprecated)
/// The GIMatchKind and GIMatchKindWithArgs cases are described in more detail
/// in their definitions below.
/// For the Instruction case, these are collected into a DAG where operand names
/// that occur multiple times introduce edges.
class GIMatchKind;
class GIMatchKindWithArgs;

/// In lieu of having proper macro support. Trivial one-off opcode checks can be
/// performed with this.
def wip_match_opcode : GIMatchKindWithArgs;

/// The operator at the root of a GICombineRule.Apply dag.
def apply;
/// All arguments of the apply operator must be subclasses of GIApplyKind, or
/// sub-dags whose operator is GIApplyKindWithArgs, or an MIR block
/// (deprecated).
class GIApplyKind;
class GIApplyKindWithArgs;

def copy_prop : GICombineRule<
  (defs root:$d),
  (match (COPY $d, $s):$mi,
         [{ return Helper.matchCombineCopy(*${mi}); }]),
  (apply [{ Helper.applyCombineCopy(*${mi}); }])>;

def extending_loads : GICombineRule<
  (defs root:$root, extending_load_matchdata:$matchinfo),
  (match (wip_match_opcode G_LOAD, G_SEXTLOAD, G_ZEXTLOAD):$root,
         [{ return Helper.matchCombineExtendingLoads(*${root}, ${matchinfo}); }]),
  (apply [{ Helper.applyCombineExtendingLoads(*${root}, ${matchinfo}); }])>;
def combines_for_extload: GICombineGroup<[extending_loads]>;

def sext_trunc_sextload : GICombineRule<
  (defs root:$d),
  (match (wip_match_opcode G_SEXT_INREG):$d,
         [{ return Helper.matchSextTruncSextLoad(*${d}); }]),
  (apply [{ Helper.applySextTruncSextLoad(*${d}); }])>;

def combine_indexed_load_store : GICombineRule<
  (defs root:$root, indexed_load_store_matchdata:$matchinfo),
  (match (wip_match_opcode G_LOAD, G_SEXTLOAD, G_ZEXTLOAD, G_STORE):$root,
         [{ return Helper.matchCombineIndexedLoadStore(*${root}, ${matchinfo}); }]),
  (apply [{ Helper.applyCombineIndexedLoadStore(*${root}, ${matchinfo}); }])>;

// FIXME: Is there a reason this wasn't in tryCombine? I've left it out of
//        all_combines because it wasn't there.
def elide_br_by_inverting_cond : GICombineRule<
  (defs root:$root),
  (match (wip_match_opcode G_BR):$root,
         [{ return Helper.matchElideBrByInvertingCond(*${root}); }]),
  (apply [{ Helper.applyElideBrByInvertingCond(*${root}); }])>;

def ptr_add_immed_matchdata : GIDefMatchData<"PtrAddChain">;
def ptr_add_immed_chain : GICombineRule<
  (defs root:$d, ptr_add_immed_matchdata:$matchinfo),
  (match (wip_match_opcode G_PTR_ADD):$d,
         [{ return Helper.matchPtrAddImmedChain(*${d}, ${matchinfo}); }]),
  (apply [{ Helper.applyPtrAddImmedChain(*${d}, ${matchinfo}); }])>;

def mul_to_shl_matchdata : GIDefMatchData<"unsigned">;
def mul_to_shl : GICombineRule<
  (defs root:$d, mul_to_shl_matchdata:$matchinfo),
  (match (G_MUL $d, $op1, $op2):$mi,
         [{ return Helper.matchCombineMulToShl(*${mi}, ${matchinfo}); }]),
  (apply [{ Helper.applyCombineMulToShl(*${mi}, ${matchinfo}); }])>;

// [us]itofp(undef) = 0, because the result value is bounded.
def undef_to_fp_zero : GICombineRule<
  (defs root:$root),
  (match (wip_match_opcode G_UITOFP, G_SITOFP):$root,
         [{ return Helper.matchAnyExplicitUseIsUndef(*${root}); }]),
  (apply [{ Helper.replaceInstWithFConstant(*${root}, 0.0); }])>;

def undef_to_int_zero: GICombineRule<
  (defs root:$root),
  (match (wip_match_opcode G_AND, G_MUL):$root,
         [{ return Helper.matchAnyExplicitUseIsUndef(*${root}); }]),
  (apply [{ Helper.replaceInstWithConstant(*${root}, 0); }])>;

def undef_to_negative_one: GICombineRule<
  (defs root:$root),
  (match (wip_match_opcode G_OR):$root,
         [{ return Helper.matchAnyExplicitUseIsUndef(*${root}); }]),
  (apply [{ Helper.replaceInstWithConstant(*${root}, -1); }])>;

// Instructions where if any source operand is undef, the instruction can be
// replaced with undef.
def propagate_undef_any_op: GICombineRule<
  (defs root:$root),
  (match (wip_match_opcode G_ADD, G_FPTOSI, G_FPTOUI, G_SUB, G_XOR):$root,
         [{ return Helper.matchAnyExplicitUseIsUndef(*${root}); }]),
  (apply [{ Helper.replaceInstWithUndef(*${root}); }])>;

// Instructions where if all source operands are undef, the instruction can be
// replaced with undef.
def propagate_undef_all_ops: GICombineRule<
  (defs root:$root),
  (match (wip_match_opcode G_SHUFFLE_VECTOR):$root,
          [{ return Helper.matchAllExplicitUsesAreUndef(*${root}); }]),
  (apply [{ Helper.replaceInstWithUndef(*${root}); }])>;

// Replace a G_SHUFFLE_VECTOR with an undef mask with a G_IMPLICIT_DEF.
def propagate_undef_shuffle_mask: GICombineRule<
  (defs root:$root),
  (match (wip_match_opcode G_SHUFFLE_VECTOR):$root,
         [{ return Helper.matchUndefShuffleVectorMask(*${root}); }]),
  (apply [{ Helper.replaceInstWithUndef(*${root}); }])>;

// Fold (cond ? x : x) -> x
def select_same_val: GICombineRule<
  (defs root:$root),
  (match (wip_match_opcode G_SELECT):$root,
    [{ return Helper.matchSelectSameVal(*${root}); }]),
  (apply [{ return Helper.replaceSingleDefInstWithOperand(*${root}, 2); }])
>;

// Fold x op 0 -> x
def right_identity_zero: GICombineRule<
  (defs root:$root),
  (match (wip_match_opcode G_SUB, G_ADD, G_OR, G_XOR, G_SHL, G_ASHR, G_LSHR):$root,
    [{ return Helper.matchConstantOp(${root}->getOperand(2), 0); }]),
  (apply [{ return Helper.replaceSingleDefInstWithOperand(*${root}, 1); }])
>;

// Fold (x op x) - > x
def binop_same_val: GICombineRule<
  (defs root:$root),
  (match (wip_match_opcode G_AND, G_OR):$root,
    [{ return Helper.matchBinOpSameVal(*${root}); }]),
  (apply [{ return Helper.replaceSingleDefInstWithOperand(*${root}, 1); }])
>;

// Fold (0 op x) - > 0
def binop_left_to_zero: GICombineRule<
  (defs root:$root),
  (match (wip_match_opcode G_SDIV, G_UDIV, G_SREM, G_UREM):$root,
    [{ return Helper.matchOperandIsZero(*${root}, 1); }]),
  (apply [{ return Helper.replaceSingleDefInstWithOperand(*${root}, 1); }])
>;

// Fold (x op 0) - > 0
def binop_right_to_zero: GICombineRule<
  (defs root:$root),
  (match (wip_match_opcode G_MUL):$root,
    [{ return Helper.matchOperandIsZero(*${root}, 2); }]),
  (apply [{ return Helper.replaceSingleDefInstWithOperand(*${root}, 2); }])
>;

// Erase stores of undef values.
def erase_undef_store : GICombineRule<
  (defs root:$root),
  (match (wip_match_opcode G_STORE):$root,
    [{ return Helper.matchUndefStore(*${root}); }]),
  (apply [{ return Helper.eraseInst(*${root}); }])
>;

def simplify_add_to_sub_matchinfo: GIDefMatchData<"std::tuple<Register, Register>">;
def simplify_add_to_sub: GICombineRule <
  (defs root:$root, simplify_add_to_sub_matchinfo:$info),
  (match (wip_match_opcode G_ADD):$root,
    [{ return Helper.matchSimplifyAddToSub(*${root}, ${info}); }]),
  (apply [{ return Helper.applySimplifyAddToSub(*${root}, ${info});}])
>;

// Fold int2ptr(ptr2int(x)) -> x
def p2i_to_i2p_matchinfo: GIDefMatchData<"Register">;
def p2i_to_i2p: GICombineRule<
  (defs root:$root, p2i_to_i2p_matchinfo:$info),
  (match (wip_match_opcode G_INTTOPTR):$root,
    [{ return Helper.matchCombineI2PToP2I(*${root}, ${info}); }]),
  (apply [{ return Helper.applyCombineI2PToP2I(*${root}, ${info}); }])
>;

// Fold ptr2int(int2ptr(x)) -> x
def i2p_to_p2i_matchinfo: GIDefMatchData<"Register">;
def i2p_to_p2i: GICombineRule<
  (defs root:$root, i2p_to_p2i_matchinfo:$info),
  (match (wip_match_opcode G_PTRTOINT):$root,
    [{ return Helper.matchCombineP2IToI2P(*${root}, ${info}); }]),
  (apply [{ return Helper.applyCombineP2IToI2P(*${root}, ${info}); }])
>;

// Simplify: (logic_op (op x...), (op y...)) -> (op (logic_op x, y))
def hoist_logic_op_with_same_opcode_hands: GICombineRule <
  (defs root:$root, instruction_steps_matchdata:$info),
  (match (wip_match_opcode G_AND, G_OR, G_XOR):$root,
    [{ return Helper.matchHoistLogicOpWithSameOpcodeHands(*${root}, ${info}); }]),
  (apply [{ return Helper.applyBuildInstructionSteps(*${root}, ${info});}])
>;

// FIXME: These should use the custom predicate feature once it lands.
def undef_combines : GICombineGroup<[undef_to_fp_zero, undef_to_int_zero,
                                     undef_to_negative_one,
                                     propagate_undef_any_op,
                                     propagate_undef_all_ops,
                                     propagate_undef_shuffle_mask,
                                     erase_undef_store]>;

def identity_combines : GICombineGroup<[select_same_val, right_identity_zero,
                                        binop_same_val, binop_left_to_zero,
                                        binop_right_to_zero, p2i_to_i2p,
                                        i2p_to_p2i]>;

def trivial_combines : GICombineGroup<[copy_prop, mul_to_shl]>;
def all_combines : GICombineGroup<[trivial_combines, ptr_add_immed_chain,
    combines_for_extload, combine_indexed_load_store, undef_combines,
    identity_combines, simplify_add_to_sub,
    hoist_logic_op_with_same_opcode_hands]>;