gcc/ccmp.c

   1 /* Conditional compare related functions
   2    Copyright (C) 2014-2014 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify it under
   7 the terms of the GNU General Public License as published by the Free
   8 Software Foundation; either version 3, or (at your option) any later
   9 version.
  10
  11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14 for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GCC; see the file COPYING3.  If not see
  18 <http://www.gnu.org/licenses/>.  */
  19
  20 #include "config.h"
  21 #include "system.h"
  22 #include "coretypes.h"
  23 #include "tm.h"
  24 #include "rtl.h"
  25 #include "tm_p.h"
  26 #include "tree.h"
  27 #include "stringpool.h"
  28 #include "stor-layout.h"
  29 #include "regs.h"
  30 #include "expr.h"
  31 #include "insn-codes.h"
  32 #include "optabs.h"
  33 #include "tree-iterator.h"
  34 #include "predict.h"
  35 #include "dominance.h"
  36 #include "cfg.h"
  37 #include "basic-block.h"
  38 #include "tree-ssa-alias.h"
  39 #include "internal-fn.h"
  40 #include "gimple-expr.h"
  41 #include "is-a.h"
  42 #include "gimple.h"
  43 #include "gimple-ssa.h"
  44 #include "tree-ssanames.h"
  45 #include "target.h"
  46 #include "common/common-target.h"
  47 #include "df.h"
  48 #include "tree-ssa-live.h"
  49 #include "tree-outof-ssa.h"
  50 #include "cfgexpand.h"
  51 #include "tree-phinodes.h"
  52 #include "ssa-iterators.h"
  53 #include "expmed.h"
  54 #include "ccmp.h"
  55
  56 /* The following functions expand conditional compare (CCMP) instructions.
  57    Here is a short description about the over all algorithm:
  58      * ccmp_candidate_p is used to identify the CCMP candidate
  59
  60      * expand_ccmp_expr is the main entry, which calls expand_ccmp_expr_1
  61        to expand CCMP.
  62
  63      * expand_ccmp_expr_1 uses a recursive algorithm to expand CCMP.
  64        It calls two target hooks gen_ccmp_first and gen_ccmp_next to generate
  65        CCMP instructions.
  66          - gen_ccmp_first expands the first compare in CCMP.
  67          - gen_ccmp_next expands the following compares.
  68
  69      * If the final result is not used in a COND_EXPR (checked by function
  70        used_in_cond_stmt_p), it calls cstorecc4 pattern to store the CC to a
  71        general register.  */
  72
  73 /* Check whether G is a potential conditional compare candidate.  */
  74 static bool
  75 ccmp_candidate_p (gimple g)
  76 {
  77   tree rhs = gimple_assign_rhs_to_tree (g);
  78   tree lhs, op0, op1;
  79   gimple gs0, gs1;
  80   enum tree_code tcode, tcode0, tcode1;
  81   tcode = TREE_CODE (rhs);
  82
  83   if (tcode != BIT_AND_EXPR && tcode != BIT_IOR_EXPR)
  84     return false;
  85
  86   lhs = gimple_assign_lhs (g);
  87   op0 = TREE_OPERAND (rhs, 0);
  88   op1 = TREE_OPERAND (rhs, 1);
  89
  90   if ((TREE_CODE (op0) != SSA_NAME) || (TREE_CODE (op1) != SSA_NAME)
  91       || !has_single_use (lhs))
  92     return false;
  93
  94   gs0 = get_gimple_for_ssa_name (op0);
  95   gs1 = get_gimple_for_ssa_name (op1);
  96   if (!gs0 || !gs1 || !is_gimple_assign (gs0) || !is_gimple_assign (gs1)
  97       /* g, gs0 and gs1 must be in the same basic block, since current stage
  98          is out-of-ssa.  We can not guarantee the correctness when forwording
  99          the gs0 and gs1 into g whithout DATAFLOW analysis.  */
 100       || gimple_bb (gs0) != gimple_bb (gs1)
 101       || gimple_bb (gs0) != gimple_bb (g))
 102     return false;
 103
 104   if (!(INTEGRAL_TYPE_P (TREE_TYPE (gimple_assign_rhs1 (gs0)))
 105        || POINTER_TYPE_P (TREE_TYPE (gimple_assign_rhs1 (gs0))))
 106       || !(INTEGRAL_TYPE_P (TREE_TYPE (gimple_assign_rhs1 (gs1)))
 107            || POINTER_TYPE_P (TREE_TYPE (gimple_assign_rhs1 (gs1)))))
 108     return false;
 109
 110   tcode0 = gimple_assign_rhs_code (gs0);
 111   tcode1 = gimple_assign_rhs_code (gs1);
 112   if (TREE_CODE_CLASS (tcode0) == tcc_comparison
 113       && TREE_CODE_CLASS (tcode1) == tcc_comparison)
 114     return true;
 115   if (TREE_CODE_CLASS (tcode0) == tcc_comparison
 116       && ccmp_candidate_p (gs1))
 117     return true;
 118   else if (TREE_CODE_CLASS (tcode1) == tcc_comparison
 119            && ccmp_candidate_p (gs0))
 120     return true;
 121   /* We skip ccmp_candidate_p (gs1) && ccmp_candidate_p (gs0) since
 122      there is no way to set the CC flag.  */
 123   return false;
 124 }
 125
 126 /* Check whether EXP is used in a GIMPLE_COND statement or not.  */
 127 static bool
 128 used_in_cond_stmt_p (tree exp)
 129 {
 130   bool expand_cond = false;
 131   imm_use_iterator ui;
 132   gimple use_stmt;
 133   FOR_EACH_IMM_USE_STMT (use_stmt, ui, exp)
 134     if (gimple_code (use_stmt) == GIMPLE_COND)
 135       {
 136         tree op1 = gimple_cond_rhs (use_stmt);
 137         if (integer_zerop (op1))
 138           expand_cond = true;
 139         BREAK_FROM_IMM_USE_STMT (ui);
 140       }
 141     else if (gimple_code (use_stmt) == GIMPLE_ASSIGN
 142              && gimple_expr_code (use_stmt) == COND_EXPR)
 143       {
 144         if (gimple_assign_rhs1 (use_stmt) == exp)
 145           expand_cond = true;
 146       }
 147
 148   return expand_cond;
 149 }
 150
 151 /* Expand conditional compare gimple G.  A typical CCMP sequence is like:
 152
 153      CC0 = CMP (a, b);
 154      CC1 = CCMP (NE (CC0, 0), CMP (e, f));
 155      ...
 156      CCn = CCMP (NE (CCn-1, 0), CMP (...));
 157
 158    hook gen_ccmp_first is used to expand the first compare.
 159    hook gen_ccmp_next is used to expand the following CCMP.  */
 160 static rtx
 161 expand_ccmp_expr_1 (gimple g)
 162 {
 163   tree exp = gimple_assign_rhs_to_tree (g);
 164   enum tree_code code = TREE_CODE (exp);
 165   gimple gs0 = get_gimple_for_ssa_name (TREE_OPERAND (exp, 0));
 166   gimple gs1 = get_gimple_for_ssa_name (TREE_OPERAND (exp, 1));
 167   rtx tmp;
 168   enum tree_code code0 = gimple_assign_rhs_code (gs0);
 169   enum tree_code code1 = gimple_assign_rhs_code (gs1);
 170
 171   gcc_assert (code == BIT_AND_EXPR || code == BIT_IOR_EXPR);
 172   gcc_assert (gs0 && gs1 && is_gimple_assign (gs0) && is_gimple_assign (gs1));
 173
 174   if (TREE_CODE_CLASS (code0) == tcc_comparison)
 175     {
 176       if (TREE_CODE_CLASS (code1) == tcc_comparison)
 177         {
 178           int unsignedp0, unsignedp1;
 179           enum rtx_code rcode0, rcode1;
 180           rtx op0, op1, op2, op3, tmp;
 181
 182           unsignedp0 = TYPE_UNSIGNED (TREE_TYPE (gimple_assign_rhs1 (gs0)));
 183           rcode0 = get_rtx_code (code0, unsignedp0);
 184           unsignedp1 = TYPE_UNSIGNED (TREE_TYPE (gimple_assign_rhs1 (gs1)));
 185           rcode1 = get_rtx_code (code1, unsignedp1);
 186
 187           expand_operands (gimple_assign_rhs1 (gs0),
 188                            gimple_assign_rhs2 (gs0),
 189                            NULL_RTX, &op0, &op1, EXPAND_NORMAL);
 190
 191           /* Since the operands of GS1 might clobber CC reg, we expand the
 192              operands of GS1 before GEN_CCMP_FIRST.  */
 193           expand_operands (gimple_assign_rhs1 (gs1),
 194                            gimple_assign_rhs2 (gs1),
 195                            NULL_RTX, &op2, &op3, EXPAND_NORMAL);
 196           tmp = targetm.gen_ccmp_first (rcode0, op0, op1);
 197           if (!tmp)
 198             return NULL_RTX;
 199
 200           return targetm.gen_ccmp_next (tmp, rcode1, op2, op3,
 201                                         get_rtx_code (code, 0));
 202         }
 203       else
 204         {
 205           rtx op0, op1;
 206           enum rtx_code rcode;
 207           int unsignedp = TYPE_UNSIGNED (TREE_TYPE (gimple_assign_rhs1 (gs0)));
 208
 209           rcode = get_rtx_code (gimple_assign_rhs_code (gs0), unsignedp);
 210
 211           /* Hoist the preparation operations above the entire
 212              conditional compare sequence.  */
 213           expand_operands (gimple_assign_rhs1 (gs0),
 214                            gimple_assign_rhs2 (gs0),
 215                            NULL_RTX, &op0, &op1, EXPAND_NORMAL);
 216
 217           gcc_assert (code1 == BIT_AND_EXPR || code1 == BIT_IOR_EXPR);
 218
 219           /* Note: We swap the order to make the recursive function work.  */
 220           tmp = expand_ccmp_expr_1 (gs1);
 221           if (tmp)
 222             return targetm.gen_ccmp_next (tmp, rcode, op0, op1,
 223                                           get_rtx_code (code, 0));
 224         }
 225     }
 226   else
 227     {
 228       gcc_assert (gimple_assign_rhs_code (gs0) == BIT_AND_EXPR
 229                   || gimple_assign_rhs_code (gs0) == BIT_IOR_EXPR);
 230
 231       if (TREE_CODE_CLASS (gimple_assign_rhs_code (gs1)) == tcc_comparison)
 232         {
 233           rtx op0, op1;
 234           enum rtx_code rcode;
 235           int unsignedp = TYPE_UNSIGNED (TREE_TYPE (gimple_assign_rhs1 (gs1)));
 236
 237           rcode = get_rtx_code (gimple_assign_rhs_code (gs1), unsignedp);
 238
 239           /* Hoist the preparation operations above the entire
 240              conditional compare sequence.  */
 241           expand_operands (gimple_assign_rhs1 (gs1),
 242                            gimple_assign_rhs2 (gs1),
 243                            NULL_RTX, &op0, &op1, EXPAND_NORMAL);
 244           tmp = expand_ccmp_expr_1 (gs0);
 245           if (tmp)
 246             return targetm.gen_ccmp_next (tmp, rcode, op0, op1,
 247                                           get_rtx_code (code, 0));
 248         }
 249       else
 250         {
 251           gcc_assert (gimple_assign_rhs_code (gs1) == BIT_AND_EXPR
 252                       || gimple_assign_rhs_code (gs1) == BIT_IOR_EXPR);
 253         }
 254     }
 255
 256   return NULL_RTX;
 257 }
 258
 259 /* Main entry to expand conditional compare statement G.
 260    Return NULL_RTX if G is not a legal candidate or expand fail.
 261    Otherwise return the target.  */
 262 rtx
 263 expand_ccmp_expr (gimple g)
 264 {
 265   rtx_insn *last;
 266   rtx tmp;
 267
 268   if (!ccmp_candidate_p (g))
 269     return NULL_RTX;
 270
 271   last = get_last_insn ();
 272   tmp = expand_ccmp_expr_1 (g);
 273
 274   if (tmp)
 275     {
 276       enum insn_code icode;
 277       enum machine_mode cc_mode = CCmode;
 278
 279       tree lhs = gimple_assign_lhs (g);
 280       /* TMP should be CC.  If it is used in a GIMPLE_COND, just return it.
 281          Note: Target needs to define "cbranchcc4".  */
 282       if (used_in_cond_stmt_p (lhs))
 283         return tmp;
 284
 285 #ifdef SELECT_CC_MODE
 286       cc_mode = SELECT_CC_MODE (NE, tmp, const0_rtx);
 287 #endif
 288       /* If TMP is not used in a GIMPLE_COND, store it with a csctorecc4_optab.
 289          Note: Target needs to define "cstorecc4".  */
 290       icode = optab_handler (cstore_optab, cc_mode);
 291       if (icode != CODE_FOR_nothing)
 292         {
 293           tree lhs = gimple_assign_lhs (g);
 294           enum machine_mode mode = TYPE_MODE (TREE_TYPE (lhs));
 295           rtx target = gen_reg_rtx (mode);
 296           tmp = emit_cstore (target, icode, NE, cc_mode, cc_mode,
 297                              0, tmp, const0_rtx, 1, mode);
 298           if (tmp)
 299             return tmp;
 300         }
 301     }
 302   /* Clean up.  */
 303   delete_insns_since (last);
 304   return NULL_RTX;
 305 }
 306