ccmp.c

/* Conditional compare related functions
   Copyright (C) 2014-2015 Free Software Foundation, Inc.

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "backend.h"
#include "tree.h"
#include "gimple.h"
#include "rtl.h"
#include "df.h"
#include "ssa.h"
#include "tm_p.h"
#include "alias.h"
#include "fold-const.h"
#include "stor-layout.h"
#include "regs.h"
#include "flags.h"
#include "insn-config.h"
#include "expmed.h"
#include "dojump.h"
#include "explow.h"
#include "calls.h"
#include "emit-rtl.h"
#include "varasm.h"
#include "stmt.h"
#include "expr.h"
#include "insn-codes.h"
#include "optabs.h"
#include "tree-iterator.h"
#include "internal-fn.h"
#include "target.h"
#include "common/common-target.h"
#include "tree-ssa-live.h"
#include "tree-outof-ssa.h"
#include "cfgexpand.h"
#include "ccmp.h"

/* The following functions expand conditional compare (CCMP) instructions.
   Here is a short description about the over all algorithm:
     * ccmp_candidate_p is used to identify the CCMP candidate

     * expand_ccmp_expr is the main entry, which calls expand_ccmp_expr_1
       to expand CCMP.

     * expand_ccmp_expr_1 uses a recursive algorithm to expand CCMP.
       It calls two target hooks gen_ccmp_first and gen_ccmp_next to generate
       CCMP instructions.
	 - gen_ccmp_first expands the first compare in CCMP.
	 - gen_ccmp_next expands the following compares.

     * We use cstorecc4 pattern to convert the CCmode intermediate to
       the integer mode result that expand_normal is expecting.

   Since the operands of the later compares might clobber CC reg, we do not
   emit the insns during expand.  We keep the insn sequences in two seq

     * prep_seq, which includes all the insns to prepare the operands.
     * gen_seq, which includes all the compare and conditional compares.

   If all checks OK in expand_ccmp_expr, it emits insns in prep_seq, then
   insns in gen_seq.  */

/* Check whether G is a potential conditional compare candidate.  */
static bool
ccmp_candidate_p (gimple g)
{
  tree rhs = gimple_assign_rhs_to_tree (g);
  tree lhs, op0, op1;
  gimple gs0, gs1;
  enum tree_code tcode, tcode0, tcode1;
  tcode = TREE_CODE (rhs);

  if (tcode != BIT_AND_EXPR && tcode != BIT_IOR_EXPR)
    return false;

  lhs = gimple_assign_lhs (g);
  op0 = TREE_OPERAND (rhs, 0);
  op1 = TREE_OPERAND (rhs, 1);

  if ((TREE_CODE (op0) != SSA_NAME) || (TREE_CODE (op1) != SSA_NAME)
      || !has_single_use (lhs))
    return false;

  gs0 = get_gimple_for_ssa_name (op0);
  gs1 = get_gimple_for_ssa_name (op1);
  if (!gs0 || !gs1 || !is_gimple_assign (gs0) || !is_gimple_assign (gs1)
      /* g, gs0 and gs1 must be in the same basic block, since current stage
	 is out-of-ssa.  We can not guarantee the correctness when forwording
	 the gs0 and gs1 into g whithout DATAFLOW analysis.  */
      || gimple_bb (gs0) != gimple_bb (gs1)
      || gimple_bb (gs0) != gimple_bb (g))
    return false;

  if (!(INTEGRAL_TYPE_P (TREE_TYPE (gimple_assign_rhs1 (gs0)))
       || POINTER_TYPE_P (TREE_TYPE (gimple_assign_rhs1 (gs0))))
      || !(INTEGRAL_TYPE_P (TREE_TYPE (gimple_assign_rhs1 (gs1)))
	   || POINTER_TYPE_P (TREE_TYPE (gimple_assign_rhs1 (gs1)))))
    return false;

  tcode0 = gimple_assign_rhs_code (gs0);
  tcode1 = gimple_assign_rhs_code (gs1);
  if (TREE_CODE_CLASS (tcode0) == tcc_comparison
      && TREE_CODE_CLASS (tcode1) == tcc_comparison)
    return true;
  if (TREE_CODE_CLASS (tcode0) == tcc_comparison
      && ccmp_candidate_p (gs1))
    return true;
  else if (TREE_CODE_CLASS (tcode1) == tcc_comparison
	   && ccmp_candidate_p (gs0))
    return true;
  /* We skip ccmp_candidate_p (gs1) && ccmp_candidate_p (gs0) since
     there is no way to set the CC flag.  */
  return false;
}

/* PREV is the CC flag from precvious compares.  The function expands the
   next compare based on G which ops previous compare with CODE.
   PREP_SEQ returns all insns to prepare opearands for compare.
   GEN_SEQ returnss all compare insns.  */
static rtx
expand_ccmp_next (gimple g, enum tree_code code, rtx prev,
		  rtx *prep_seq, rtx *gen_seq)
{
  enum rtx_code rcode;
  int unsignedp = TYPE_UNSIGNED (TREE_TYPE (gimple_assign_rhs1 (g)));

  gcc_assert (code == BIT_AND_EXPR || code == BIT_IOR_EXPR);

  rcode = get_rtx_code (gimple_assign_rhs_code (g), unsignedp);

  return targetm.gen_ccmp_next (prep_seq, gen_seq, prev, rcode,
				gimple_assign_rhs1 (g),
				gimple_assign_rhs2 (g),
				get_rtx_code (code, 0));
}

/* Expand conditional compare gimple G.  A typical CCMP sequence is like:

     CC0 = CMP (a, b);
     CC1 = CCMP (NE (CC0, 0), CMP (e, f));
     ...
     CCn = CCMP (NE (CCn-1, 0), CMP (...));

   hook gen_ccmp_first is used to expand the first compare.
   hook gen_ccmp_next is used to expand the following CCMP.
   PREP_SEQ returns all insns to prepare opearand.
   GEN_SEQ returns all compare insns.  */
static rtx
expand_ccmp_expr_1 (gimple g, rtx *prep_seq, rtx *gen_seq)
{
  tree exp = gimple_assign_rhs_to_tree (g);
  enum tree_code code = TREE_CODE (exp);
  gimple gs0 = get_gimple_for_ssa_name (TREE_OPERAND (exp, 0));
  gimple gs1 = get_gimple_for_ssa_name (TREE_OPERAND (exp, 1));
  rtx tmp;
  enum tree_code code0 = gimple_assign_rhs_code (gs0);
  enum tree_code code1 = gimple_assign_rhs_code (gs1);

  gcc_assert (code == BIT_AND_EXPR || code == BIT_IOR_EXPR);
  gcc_assert (gs0 && gs1 && is_gimple_assign (gs0) && is_gimple_assign (gs1));

  if (TREE_CODE_CLASS (code0) == tcc_comparison)
    {
      if (TREE_CODE_CLASS (code1) == tcc_comparison)
	{
	  int unsignedp0;
	  enum rtx_code rcode0;

	  unsignedp0 = TYPE_UNSIGNED (TREE_TYPE (gimple_assign_rhs1 (gs0)));
	  rcode0 = get_rtx_code (code0, unsignedp0);

	  tmp = targetm.gen_ccmp_first (prep_seq, gen_seq, rcode0,
					gimple_assign_rhs1 (gs0),
					gimple_assign_rhs2 (gs0));
	  if (!tmp)
	    return NULL_RTX;

	  return expand_ccmp_next (gs1, code, tmp, prep_seq, gen_seq);
	}
      else
	{
	  tmp = expand_ccmp_expr_1 (gs1, prep_seq, gen_seq);
	  if (!tmp)
	    return NULL_RTX;

	  return expand_ccmp_next (gs0, code, tmp, prep_seq, gen_seq);
	}
    }
  else
    {
      gcc_assert (gimple_assign_rhs_code (gs0) == BIT_AND_EXPR
                  || gimple_assign_rhs_code (gs0) == BIT_IOR_EXPR);

      if (TREE_CODE_CLASS (gimple_assign_rhs_code (gs1)) == tcc_comparison)
	{
	  tmp = expand_ccmp_expr_1 (gs0, prep_seq, gen_seq);
	  if (!tmp)
	    return NULL_RTX;

	  return expand_ccmp_next (gs1, code, tmp, prep_seq, gen_seq);
	}
      else
	{
	  gcc_assert (gimple_assign_rhs_code (gs1) == BIT_AND_EXPR
		      || gimple_assign_rhs_code (gs1) == BIT_IOR_EXPR);
	}
    }

  return NULL_RTX;
}

/* Main entry to expand conditional compare statement G. 
   Return NULL_RTX if G is not a legal candidate or expand fail.
   Otherwise return the target.  */
rtx
expand_ccmp_expr (gimple g)
{
  rtx_insn *last;
  rtx tmp;
  rtx prep_seq, gen_seq;

  prep_seq = gen_seq = NULL_RTX;

  if (!ccmp_candidate_p (g))
    return NULL_RTX;

  last = get_last_insn ();
  tmp = expand_ccmp_expr_1 (g, &prep_seq, &gen_seq);

  if (tmp)
    {
      enum insn_code icode;
      enum machine_mode cc_mode = CCmode;
      tree lhs = gimple_assign_lhs (g);

#ifdef SELECT_CC_MODE
      cc_mode = SELECT_CC_MODE (NE, tmp, const0_rtx);
#endif
      icode = optab_handler (cstore_optab, cc_mode);
      if (icode != CODE_FOR_nothing)
	{
	  enum machine_mode mode = TYPE_MODE (TREE_TYPE (lhs));
	  rtx target = gen_reg_rtx (mode);

	  emit_insn (prep_seq);
	  emit_insn (gen_seq);

	  tmp = emit_cstore (target, icode, NE, cc_mode, cc_mode,
			     0, tmp, const0_rtx, 1, mode);
	  if (tmp)
	    return tmp;
	}
    }
  /* Clean up.  */
  delete_insns_since (last);
  return NULL_RTX;
}