Initial checkin of GCC 4.9.0 from trunk (r208799).

Change-Id: I48a3c08bb98542aa215912a75f03c0890e497dba

1 files changed, 965 insertions, 0 deletions

diff --git a/gcc-4.9/gcc/tree-call-cdce.c b/gcc-4.9/gcc/tree-call-cdce.c
new file mode 100644
index 000000000..4b2ad87c0
--- /dev/null
+++ b/gcc-4.9/gcc/tree-call-cdce.c
@@ -0,0 +1,965 @@
+/* Conditional Dead Call Elimination pass for the GNU compiler.
+   Copyright (C) 2008-2014 Free Software Foundation, Inc.
+   Contributed by Xinliang David Li <davidxl@google.com>
+
+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 "tm.h"
+#include "basic-block.h"
+#include "tree.h"
+#include "stor-layout.h"
+#include "gimple-pretty-print.h"
+#include "tree-ssa-alias.h"
+#include "internal-fn.h"
+#include "gimple-expr.h"
+#include "is-a.h"
+#include "gimple.h"
+#include "gimple-iterator.h"
+#include "gimple-ssa.h"
+#include "tree-cfg.h"
+#include "stringpool.h"
+#include "tree-ssanames.h"
+#include "tree-into-ssa.h"
+#include "tree-pass.h"
+#include "flags.h"
+
+
+/* Conditional dead call elimination
+
+   Some builtin functions can set errno on error conditions, but they
+   are otherwise pure.  If the result of a call to such a function is
+   not used, the compiler can still not eliminate the call without
+   powerful interprocedural analysis to prove that the errno is not
+   checked.  However, if the conditions under which the error occurs
+   are known, the compiler can conditionally dead code eliminate the
+   calls by shrink-wrapping the semi-dead calls into the error condition:
+
+        built_in_call (args)
+          ==>
+        if (error_cond (args))
+             built_in_call (args)
+
+    An actual simple example is :
+         log (x);   // Mostly dead call
+     ==>
+         if (x < 0)
+             log (x);
+     With this change, call to log (x) is effectively eliminated, as
+     in majority of the cases, log won't be called with x out of
+     range.  The branch is totally predictable, so the branch cost
+     is low.
+
+   Note that library functions are not supposed to clear errno to zero without
+   error.  See IEEE Std 1003.1, section 2.3 Error Numbers, and section 7.5:3 of
+   ISO/IEC 9899 (C99).
+
+   The condition wrapping the builtin call is conservatively set to avoid too
+   aggressive (wrong) shrink wrapping.  The optimization is called conditional
+   dead call elimination because the call is eliminated under the condition
+   that the input arguments would not lead to domain or range error (for
+   instance when x <= 0 for a log (x) call), however the chances that the error
+   condition is hit is very low (those builtin calls which are conditionally
+   dead are usually part of the C++ abstraction penalty exposed after
+   inlining).  */
+
+
+/* A structure for representing input domain of
+   a function argument in integer.  If the lower
+   bound is -inf, has_lb is set to false.  If the
+   upper bound is +inf, has_ub is false.
+   is_lb_inclusive and is_ub_inclusive are flags
+   to indicate if lb and ub value are inclusive
+   respectively.  */
+
+typedef struct input_domain
+{
+  int lb;
+  int ub;
+  bool has_lb;
+  bool has_ub;
+  bool is_lb_inclusive;
+  bool is_ub_inclusive;
+} inp_domain;
+
+/* A helper function to construct and return an input
+   domain object.  LB is the lower bound, HAS_LB is
+   a boolean flag indicating if the lower bound exists,
+   and LB_INCLUSIVE is a boolean flag indicating if the
+   lower bound is inclusive or not.  UB, HAS_UB, and
+   UB_INCLUSIVE have the same meaning, but for upper
+   bound of the domain.  */
+
+static inp_domain
+get_domain (int lb, bool has_lb, bool lb_inclusive,
+            int ub, bool has_ub, bool ub_inclusive)
+{
+  inp_domain domain;
+  domain.lb = lb;
+  domain.has_lb = has_lb;
+  domain.is_lb_inclusive = lb_inclusive;
+  domain.ub = ub;
+  domain.has_ub = has_ub;
+  domain.is_ub_inclusive = ub_inclusive;
+  return domain;
+}
+
+/* A helper function to check the target format for the
+   argument type. In this implementation, only IEEE formats
+   are supported.  ARG is the call argument to be checked.
+   Returns true if the format is supported.  To support other
+   target formats,  function get_no_error_domain needs to be
+   enhanced to have range bounds properly computed. Since
+   the check is cheap (very small number of candidates
+   to be checked), the result is not cached for each float type.  */
+
+static bool
+check_target_format (tree arg)
+{
+  tree type;
+  enum machine_mode mode;
+  const struct real_format *rfmt;
+
+  type = TREE_TYPE (arg);
+  mode = TYPE_MODE (type);
+  rfmt = REAL_MODE_FORMAT (mode);
+  if ((mode == SFmode
+       && (rfmt == &ieee_single_format || rfmt == &mips_single_format
+	   || rfmt == &motorola_single_format))
+      || (mode == DFmode
+	  && (rfmt == &ieee_double_format || rfmt == &mips_double_format
+	      || rfmt == &motorola_double_format))
+      /* For long double, we can not really check XFmode
+         which is only defined on intel platforms.
+         Candidate pre-selection using builtin function
+         code guarantees that we are checking formats
+         for long double modes: double, quad, and extended.  */
+      || (mode != SFmode && mode != DFmode
+          && (rfmt == &ieee_quad_format
+	      || rfmt == &mips_quad_format
+	      || rfmt == &ieee_extended_motorola_format
+              || rfmt == &ieee_extended_intel_96_format
+              || rfmt == &ieee_extended_intel_128_format
+              || rfmt == &ieee_extended_intel_96_round_53_format)))
+    return true;
+
+  return false;
+}
+
+
+/* A helper function to help select calls to pow that are suitable for
+   conditional DCE transformation.  It looks for pow calls that can be
+   guided with simple conditions.  Such calls either have constant base
+   values or base values converted from integers.  Returns true if
+   the pow call POW_CALL is a candidate.  */
+
+/* The maximum integer bit size for base argument of a pow call
+   that is suitable for shrink-wrapping transformation.  */
+#define MAX_BASE_INT_BIT_SIZE 32
+
+static bool
+check_pow (gimple pow_call)
+{
+  tree base, expn;
+  enum tree_code bc, ec;
+
+  if (gimple_call_num_args (pow_call) != 2)
+    return false;
+
+  base = gimple_call_arg (pow_call, 0);
+  expn = gimple_call_arg (pow_call, 1);
+
+  if (!check_target_format (expn))
+    return false;
+
+  bc = TREE_CODE (base);
+  ec = TREE_CODE (expn);
+
+  /* Folding candidates are not interesting.
+     Can actually assert that it is already folded.  */
+  if (ec == REAL_CST && bc == REAL_CST)
+    return false;
+
+  if (bc == REAL_CST)
+    {
+      /* Only handle a fixed range of constant.  */
+      REAL_VALUE_TYPE mv;
+      REAL_VALUE_TYPE bcv = TREE_REAL_CST (base);
+      if (REAL_VALUES_EQUAL (bcv, dconst1))
+        return false;
+      if (REAL_VALUES_LESS (bcv, dconst1))
+        return false;
+      real_from_integer (&mv, TYPE_MODE (TREE_TYPE (base)), 256, 0, 1);
+      if (REAL_VALUES_LESS (mv, bcv))
+        return false;
+      return true;
+    }
+  else if (bc == SSA_NAME)
+    {
+      tree base_val0, type;
+      gimple base_def;
+      int bit_sz;
+
+      /* Only handles cases where base value is converted
+         from integer values.  */
+      base_def = SSA_NAME_DEF_STMT (base);
+      if (gimple_code (base_def) != GIMPLE_ASSIGN)
+        return false;
+
+      if (gimple_assign_rhs_code (base_def) != FLOAT_EXPR)
+        return false;
+      base_val0 = gimple_assign_rhs1 (base_def);
+
+      type = TREE_TYPE (base_val0);
+      if (TREE_CODE (type) != INTEGER_TYPE)
+        return false;
+      bit_sz = TYPE_PRECISION (type);
+      /* If the type of the base is too wide,
+         the resulting shrink wrapping condition
+	 will be too conservative.  */
+      if (bit_sz > MAX_BASE_INT_BIT_SIZE)
+        return false;
+
+      return true;
+    }
+  else
+    return false;
+}
+
+/* A helper function to help select candidate function calls that are
+   suitable for conditional DCE.  Candidate functions must have single
+   valid input domain in this implementation except for pow (see check_pow).
+   Returns true if the function call is a candidate.  */
+
+static bool
+check_builtin_call (gimple bcall)
+{
+  tree arg;
+
+  arg = gimple_call_arg (bcall, 0);
+  return check_target_format (arg);
+}
+
+/* A helper function to determine if a builtin function call is a
+   candidate for conditional DCE.  Returns true if the builtin call
+   is a candidate.  */
+
+static bool
+is_call_dce_candidate (gimple call)
+{
+  tree fn;
+  enum built_in_function fnc;
+
+  /* Only potentially dead calls are considered.  */
+  if (gimple_call_lhs (call))
+    return false;
+
+  fn = gimple_call_fndecl (call);
+  if (!fn
+      || !DECL_BUILT_IN (fn)
+      || (DECL_BUILT_IN_CLASS (fn) != BUILT_IN_NORMAL))
+    return false;
+
+  fnc = DECL_FUNCTION_CODE (fn);
+  switch (fnc)
+    {
+    /* Trig functions.  */
+    CASE_FLT_FN (BUILT_IN_ACOS):
+    CASE_FLT_FN (BUILT_IN_ASIN):
+    /* Hyperbolic functions.  */
+    CASE_FLT_FN (BUILT_IN_ACOSH):
+    CASE_FLT_FN (BUILT_IN_ATANH):
+    CASE_FLT_FN (BUILT_IN_COSH):
+    CASE_FLT_FN (BUILT_IN_SINH):
+    /* Log functions.  */
+    CASE_FLT_FN (BUILT_IN_LOG):
+    CASE_FLT_FN (BUILT_IN_LOG2):
+    CASE_FLT_FN (BUILT_IN_LOG10):
+    CASE_FLT_FN (BUILT_IN_LOG1P):
+    /* Exp functions.  */
+    CASE_FLT_FN (BUILT_IN_EXP):
+    CASE_FLT_FN (BUILT_IN_EXP2):
+    CASE_FLT_FN (BUILT_IN_EXP10):
+    CASE_FLT_FN (BUILT_IN_EXPM1):
+    CASE_FLT_FN (BUILT_IN_POW10):
+    /* Sqrt.  */
+    CASE_FLT_FN (BUILT_IN_SQRT):
+      return check_builtin_call (call);
+    /* Special one: two argument pow.  */
+    case BUILT_IN_POW:
+      return check_pow (call);
+    default:
+      break;
+    }
+
+  return false;
+}
+
+
+/* A helper function to generate gimple statements for
+   one bound comparison.  ARG is the call argument to
+   be compared with the bound, LBUB is the bound value
+   in integer, TCODE is the tree_code of the comparison,
+   TEMP_NAME1/TEMP_NAME2 are names of the temporaries,
+   CONDS is a vector holding the produced GIMPLE statements,
+   and NCONDS points to the variable holding the number
+   of logical comparisons.  CONDS is either empty or
+   a list ended with a null tree.  */
+
+static void
+gen_one_condition (tree arg, int lbub,
+                   enum tree_code tcode,
+                   const char *temp_name1,
+		   const char *temp_name2,
+                   vec<gimple> conds,
+                   unsigned *nconds)
+{
+  tree lbub_real_cst, lbub_cst, float_type;
+  tree temp, tempn, tempc, tempcn;
+  gimple stmt1, stmt2, stmt3;
+
+  float_type = TREE_TYPE (arg);
+  lbub_cst = build_int_cst (integer_type_node, lbub);
+  lbub_real_cst = build_real_from_int_cst (float_type, lbub_cst);
+
+  temp = create_tmp_var (float_type, temp_name1);
+  stmt1 = gimple_build_assign (temp, arg);
+  tempn = make_ssa_name (temp, stmt1);
+  gimple_assign_set_lhs (stmt1, tempn);
+
+  tempc = create_tmp_var (boolean_type_node, temp_name2);
+  stmt2 = gimple_build_assign (tempc,
+                               fold_build2 (tcode,
+					    boolean_type_node,
+					    tempn, lbub_real_cst));
+  tempcn = make_ssa_name (tempc, stmt2);
+  gimple_assign_set_lhs (stmt2, tempcn);
+
+  stmt3 = gimple_build_cond_from_tree (tempcn, NULL_TREE, NULL_TREE);
+  conds.quick_push (stmt1);
+  conds.quick_push (stmt2);
+  conds.quick_push (stmt3);
+  (*nconds)++;
+}
+
+/* A helper function to generate GIMPLE statements for
+   out of input domain check.  ARG is the call argument
+   to be runtime checked, DOMAIN holds the valid domain
+   for the given function, CONDS points to the vector
+   holding the result GIMPLE statements.  *NCONDS is
+   the number of logical comparisons.  This function
+   produces no more than two logical comparisons, one
+   for lower bound check, one for upper bound check.  */
+
+static void
+gen_conditions_for_domain (tree arg, inp_domain domain,
+                           vec<gimple> conds,
+                           unsigned *nconds)
+{
+  if (domain.has_lb)
+    gen_one_condition (arg, domain.lb,
+                       (domain.is_lb_inclusive
+                        ? LT_EXPR : LE_EXPR),
+                       "DCE_COND_LB", "DCE_COND_LB_TEST",
+                       conds, nconds);
+
+  if (domain.has_ub)
+    {
+      /* Now push a separator.  */
+      if (domain.has_lb)
+        conds.quick_push (NULL);
+
+      gen_one_condition (arg, domain.ub,
+                         (domain.is_ub_inclusive
+                          ? GT_EXPR : GE_EXPR),
+                         "DCE_COND_UB", "DCE_COND_UB_TEST",
+                         conds, nconds);
+    }
+}
+
+
+/* A helper function to generate condition
+   code for the y argument in call pow (some_const, y).
+   See candidate selection in check_pow.  Since the
+   candidates' base values have a limited range,
+   the guarded code generated for y are simple:
+   if (y > max_y)
+     pow (const, y);
+   Note max_y can be computed separately for each
+   const base, but in this implementation, we
+   choose to compute it using the max base
+   in the allowed range for the purpose of
+   simplicity.  BASE is the constant base value,
+   EXPN is the expression for the exponent argument,
+   *CONDS is the vector to hold resulting statements,
+   and *NCONDS is the number of logical conditions.  */
+
+static void
+gen_conditions_for_pow_cst_base (tree base, tree expn,
+                                 vec<gimple> conds,
+                                 unsigned *nconds)
+{
+  inp_domain exp_domain;
+  /* Validate the range of the base constant to make
+     sure it is consistent with check_pow.  */
+  REAL_VALUE_TYPE mv;
+  REAL_VALUE_TYPE bcv = TREE_REAL_CST (base);
+  gcc_assert (!REAL_VALUES_EQUAL (bcv, dconst1)
+              && !REAL_VALUES_LESS (bcv, dconst1));
+  real_from_integer (&mv, TYPE_MODE (TREE_TYPE (base)), 256, 0, 1);
+  gcc_assert (!REAL_VALUES_LESS (mv, bcv));
+
+  exp_domain = get_domain (0, false, false,
+                           127, true, false);
+
+  gen_conditions_for_domain (expn, exp_domain,
+                             conds, nconds);
+}
+
+/* Generate error condition code for pow calls with
+   non constant base values.  The candidates selected
+   have their base argument value converted from
+   integer (see check_pow) value (1, 2, 4 bytes), and
+   the max exp value is computed based on the size
+   of the integer type (i.e. max possible base value).
+   The resulting input domain for exp argument is thus
+   conservative (smaller than the max value allowed by
+   the runtime value of the base).  BASE is the integer
+   base value, EXPN is the expression for the exponent
+   argument, *CONDS is the vector to hold resulting
+   statements, and *NCONDS is the number of logical
+   conditions.  */
+
+static void
+gen_conditions_for_pow_int_base (tree base, tree expn,
+                                 vec<gimple> conds,
+                                 unsigned *nconds)
+{
+  gimple base_def;
+  tree base_val0;
+  tree int_type;
+  tree temp, tempn;
+  tree cst0;
+  gimple stmt1, stmt2;
+  int bit_sz, max_exp;
+  inp_domain exp_domain;
+
+  base_def = SSA_NAME_DEF_STMT (base);
+  base_val0 = gimple_assign_rhs1 (base_def);
+  int_type = TREE_TYPE (base_val0);
+  bit_sz = TYPE_PRECISION (int_type);
+  gcc_assert (bit_sz > 0
+              && bit_sz <= MAX_BASE_INT_BIT_SIZE);
+
+  /* Determine the max exp argument value according to
+     the size of the base integer.  The max exp value
+     is conservatively estimated assuming IEEE754 double
+     precision format.  */
+  if (bit_sz == 8)
+    max_exp = 128;
+  else if (bit_sz == 16)
+    max_exp = 64;
+  else
+    {
+      gcc_assert (bit_sz == MAX_BASE_INT_BIT_SIZE);
+      max_exp = 32;
+    }
+
+  /* For pow ((double)x, y), generate the following conditions:
+     cond 1:
+     temp1 = x;
+     if (temp1 <= 0)
+
+     cond 2:
+     temp2 = y;
+     if (temp2 > max_exp_real_cst)  */
+
+  /* Generate condition in reverse order -- first
+     the condition for the exp argument.  */
+
+  exp_domain = get_domain (0, false, false,
+                           max_exp, true, true);
+
+  gen_conditions_for_domain (expn, exp_domain,
+                             conds, nconds);
+
+  /* Now generate condition for the base argument.
+     Note it does not use the helper function
+     gen_conditions_for_domain because the base
+     type is integer.  */
+
+  /* Push a separator.  */
+  conds.quick_push (NULL);
+
+  temp = create_tmp_var (int_type, "DCE_COND1");
+  cst0 = build_int_cst (int_type, 0);
+  stmt1 = gimple_build_assign (temp, base_val0);
+  tempn = make_ssa_name (temp, stmt1);
+  gimple_assign_set_lhs (stmt1, tempn);
+  stmt2 = gimple_build_cond (LE_EXPR, tempn, cst0, NULL_TREE, NULL_TREE);
+
+  conds.quick_push (stmt1);
+  conds.quick_push (stmt2);
+  (*nconds)++;
+}
+
+/* Method to generate conditional statements for guarding conditionally
+   dead calls to pow.  One or more statements can be generated for
+   each logical condition.  Statement groups of different conditions
+   are separated by a NULL tree and they are stored in the vec
+   conds.  The number of logical conditions are stored in *nconds.
+
+   See C99 standard, 7.12.7.4:2, for description of pow (x, y).
+   The precise condition for domain errors are complex.  In this
+   implementation, a simplified (but conservative) valid domain
+   for x and y are used: x is positive to avoid dom errors, while
+   y is smaller than a upper bound (depending on x) to avoid range
+   errors.  Runtime code is generated to check x (if not constant)
+   and y against the valid domain.  If it is out, jump to the call,
+   otherwise the call is bypassed.  POW_CALL is the call statement,
+   *CONDS is a vector holding the resulting condition statements,
+   and *NCONDS is the number of logical conditions.  */
+
+static void
+gen_conditions_for_pow (gimple pow_call, vec<gimple> conds,
+                        unsigned *nconds)
+{
+  tree base, expn;
+  enum tree_code bc;
+
+  gcc_checking_assert (check_pow (pow_call));
+
+  *nconds = 0;
+
+  base = gimple_call_arg (pow_call, 0);
+  expn = gimple_call_arg (pow_call, 1);
+
+  bc = TREE_CODE (base);
+
+  if (bc == REAL_CST)
+    gen_conditions_for_pow_cst_base (base, expn, conds, nconds);
+  else if (bc == SSA_NAME)
+    gen_conditions_for_pow_int_base (base, expn, conds, nconds);
+  else
+    gcc_unreachable ();
+}
+
+/* A helper routine to help computing the valid input domain
+   for a builtin function.  See C99 7.12.7 for details.  In this
+   implementation, we only handle single region domain.  The
+   resulting region can be conservative (smaller) than the actual
+   one and rounded to integers.  Some of the bounds are documented
+   in the standard, while other limit constants are computed
+   assuming IEEE floating point format (for SF and DF modes).
+   Since IEEE only sets minimum requirements for long double format,
+   different long double formats exist under different implementations
+   (e.g, 64 bit double precision (DF), 80 bit double-extended
+   precision (XF), and 128 bit quad precision (QF) ).  For simplicity,
+   in this implementation, the computed bounds for long double assume
+   64 bit format (DF), and are therefore conservative.  Another
+   assumption is that single precision float type is always SF mode,
+   and double type is DF mode.  This function is quite
+   implementation specific, so it may not be suitable to be part of
+   builtins.c.  This needs to be revisited later to see if it can
+   be leveraged in x87 assembly expansion.  */
+
+static inp_domain
+get_no_error_domain (enum built_in_function fnc)
+{
+  switch (fnc)
+    {
+    /* Trig functions: return [-1, +1]  */
+    CASE_FLT_FN (BUILT_IN_ACOS):
+    CASE_FLT_FN (BUILT_IN_ASIN):
+      return get_domain (-1, true, true,
+                         1, true, true);
+    /* Hyperbolic functions.  */
+    CASE_FLT_FN (BUILT_IN_ACOSH):
+      /* acosh: [1, +inf)  */
+      return get_domain (1, true, true,
+                         1, false, false);
+    CASE_FLT_FN (BUILT_IN_ATANH):
+      /* atanh: (-1, +1)  */
+      return get_domain (-1, true, false,
+                         1, true, false);
+    case BUILT_IN_COSHF:
+    case BUILT_IN_SINHF:
+      /* coshf: (-89, +89)  */
+      return get_domain (-89, true, false,
+                         89, true, false);
+    case BUILT_IN_COSH:
+    case BUILT_IN_SINH:
+    case BUILT_IN_COSHL:
+    case BUILT_IN_SINHL:
+      /* cosh: (-710, +710)  */
+      return get_domain (-710, true, false,
+                         710, true, false);
+    /* Log functions: (0, +inf)  */
+    CASE_FLT_FN (BUILT_IN_LOG):
+    CASE_FLT_FN (BUILT_IN_LOG2):
+    CASE_FLT_FN (BUILT_IN_LOG10):
+      return get_domain (0, true, false,
+                         0, false, false);
+    CASE_FLT_FN (BUILT_IN_LOG1P):
+      return get_domain (-1, true, false,
+                         0, false, false);
+    /* Exp functions.  */
+    case BUILT_IN_EXPF:
+    case BUILT_IN_EXPM1F:
+      /* expf: (-inf, 88)  */
+      return get_domain (-1, false, false,
+                         88, true, false);
+    case BUILT_IN_EXP:
+    case BUILT_IN_EXPM1:
+    case BUILT_IN_EXPL:
+    case BUILT_IN_EXPM1L:
+      /* exp: (-inf, 709)  */
+      return get_domain (-1, false, false,
+                         709, true, false);
+    case BUILT_IN_EXP2F:
+      /* exp2f: (-inf, 128)  */
+      return get_domain (-1, false, false,
+                         128, true, false);
+    case BUILT_IN_EXP2:
+    case BUILT_IN_EXP2L:
+      /* exp2: (-inf, 1024)  */
+      return get_domain (-1, false, false,
+                         1024, true, false);
+    case BUILT_IN_EXP10F:
+    case BUILT_IN_POW10F:
+      /* exp10f: (-inf, 38)  */
+      return get_domain (-1, false, false,
+                         38, true, false);
+    case BUILT_IN_EXP10:
+    case BUILT_IN_POW10:
+    case BUILT_IN_EXP10L:
+    case BUILT_IN_POW10L:
+      /* exp10: (-inf, 308)  */
+      return get_domain (-1, false, false,
+                         308, true, false);
+    /* sqrt: [0, +inf)  */
+    CASE_FLT_FN (BUILT_IN_SQRT):
+      return get_domain (0, true, true,
+                         0, false, false);
+    default:
+      gcc_unreachable ();
+    }
+
+  gcc_unreachable ();
+}
+
+/* The function to generate shrink wrap conditions for a partially
+   dead builtin call whose return value is not used anywhere,
+   but has to be kept live due to potential error condition.
+   BI_CALL is the builtin call, CONDS is the vector of statements
+   for condition code, NCODES is the pointer to the number of
+   logical conditions.  Statements belonging to different logical
+   condition are separated by NULL tree in the vector.  */
+
+static void
+gen_shrink_wrap_conditions (gimple bi_call, vec<gimple> conds,
+                            unsigned int *nconds)
+{
+  gimple call;
+  tree fn;
+  enum built_in_function fnc;
+
+  gcc_assert (nconds && conds.exists ());
+  gcc_assert (conds.length () == 0);
+  gcc_assert (is_gimple_call (bi_call));
+
+  call = bi_call;
+  fn = gimple_call_fndecl (call);
+  gcc_assert (fn && DECL_BUILT_IN (fn));
+  fnc = DECL_FUNCTION_CODE (fn);
+  *nconds = 0;
+
+  if (fnc == BUILT_IN_POW)
+    gen_conditions_for_pow (call, conds, nconds);
+  else
+    {
+      tree arg;
+      inp_domain domain = get_no_error_domain (fnc);
+      *nconds = 0;
+      arg = gimple_call_arg (bi_call, 0);
+      gen_conditions_for_domain (arg, domain, conds, nconds);
+    }
+
+  return;
+}
+
+
+/* Probability of the branch (to the call) is taken.  */
+#define ERR_PROB 0.01
+
+/* The function to shrink wrap a partially dead builtin call
+   whose return value is not used anywhere, but has to be kept
+   live due to potential error condition.  Returns true if the
+   transformation actually happens.  */
+
+static bool
+shrink_wrap_one_built_in_call (gimple bi_call)
+{
+  gimple_stmt_iterator bi_call_bsi;
+  basic_block bi_call_bb, join_tgt_bb, guard_bb, guard_bb0;
+  edge join_tgt_in_edge_from_call, join_tgt_in_edge_fall_thru;
+  edge bi_call_in_edge0, guard_bb_in_edge;
+  unsigned tn_cond_stmts, nconds;
+  unsigned ci;
+  gimple cond_expr = NULL;
+  gimple cond_expr_start;
+  tree bi_call_label_decl;
+  gimple bi_call_label;
+
+  auto_vec<gimple, 12> conds;
+  gen_shrink_wrap_conditions (bi_call, conds, &nconds);
+
+  /* This can happen if the condition generator decides
+     it is not beneficial to do the transformation.  Just
+     return false and do not do any transformation for
+     the call.  */
+  if (nconds == 0)
+    return false;
+
+  bi_call_bb = gimple_bb (bi_call);
+
+  /* Now find the join target bb -- split bi_call_bb if needed.  */
+  if (stmt_ends_bb_p (bi_call))
+    {
+      /* If the call must be the last in the bb, don't split the block,
+	 it could e.g. have EH edges.  */
+      join_tgt_in_edge_from_call = find_fallthru_edge (bi_call_bb->succs);
+      if (join_tgt_in_edge_from_call == NULL)
+        return false;
+    }
+  else
+    join_tgt_in_edge_from_call = split_block (bi_call_bb, bi_call);
+
+  bi_call_bsi = gsi_for_stmt (bi_call);
+
+  join_tgt_bb = join_tgt_in_edge_from_call->dest;
+
+  /* Now it is time to insert the first conditional expression
+     into bi_call_bb and split this bb so that bi_call is
+     shrink-wrapped.  */
+  tn_cond_stmts = conds.length ();
+  cond_expr = NULL;
+  cond_expr_start = conds[0];
+  for (ci = 0; ci < tn_cond_stmts; ci++)
+    {
+      gimple c = conds[ci];
+      gcc_assert (c || ci != 0);
+      if (!c)
+        break;
+      gsi_insert_before (&bi_call_bsi, c, GSI_SAME_STMT);
+      cond_expr = c;
+    }
+  nconds--;
+  ci++;
+  gcc_assert (cond_expr && gimple_code (cond_expr) == GIMPLE_COND);
+
+  /* Now the label.  */
+  bi_call_label_decl = create_artificial_label (gimple_location (bi_call));
+  bi_call_label = gimple_build_label (bi_call_label_decl);
+  gsi_insert_before (&bi_call_bsi, bi_call_label, GSI_SAME_STMT);
+
+  bi_call_in_edge0 = split_block (bi_call_bb, cond_expr);
+  bi_call_in_edge0->flags &= ~EDGE_FALLTHRU;
+  bi_call_in_edge0->flags |= EDGE_TRUE_VALUE;
+  guard_bb0 = bi_call_bb;
+  bi_call_bb = bi_call_in_edge0->dest;
+  join_tgt_in_edge_fall_thru = make_edge (guard_bb0, join_tgt_bb,
+                                          EDGE_FALSE_VALUE);
+
+  bi_call_in_edge0->probability = REG_BR_PROB_BASE * ERR_PROB;
+  bi_call_in_edge0->count =
+      apply_probability (guard_bb0->count,
+			 bi_call_in_edge0->probability);
+  join_tgt_in_edge_fall_thru->probability =
+      inverse_probability (bi_call_in_edge0->probability);
+  join_tgt_in_edge_fall_thru->count =
+      guard_bb0->count - bi_call_in_edge0->count;
+
+  /* Code generation for the rest of the conditions  */
+  guard_bb = guard_bb0;
+  while (nconds > 0)
+    {
+      unsigned ci0;
+      edge bi_call_in_edge;
+      gimple_stmt_iterator guard_bsi = gsi_for_stmt (cond_expr_start);
+      ci0 = ci;
+      cond_expr_start = conds[ci0];
+      for (; ci < tn_cond_stmts; ci++)
+        {
+          gimple c = conds[ci];
+          gcc_assert (c || ci != ci0);
+          if (!c)
+            break;
+          gsi_insert_before (&guard_bsi, c, GSI_SAME_STMT);
+          cond_expr = c;
+        }
+      nconds--;
+      ci++;
+      gcc_assert (cond_expr && gimple_code (cond_expr) == GIMPLE_COND);
+      guard_bb_in_edge = split_block (guard_bb, cond_expr);
+      guard_bb_in_edge->flags &= ~EDGE_FALLTHRU;
+      guard_bb_in_edge->flags |= EDGE_FALSE_VALUE;
+
+      bi_call_in_edge = make_edge (guard_bb, bi_call_bb, EDGE_TRUE_VALUE);
+
+      bi_call_in_edge->probability = REG_BR_PROB_BASE * ERR_PROB;
+      bi_call_in_edge->count =
+	  apply_probability (guard_bb->count,
+			     bi_call_in_edge->probability);
+      guard_bb_in_edge->probability =
+          inverse_probability (bi_call_in_edge->probability);
+      guard_bb_in_edge->count = guard_bb->count - bi_call_in_edge->count;
+    }
+
+  if (dump_file && (dump_flags & TDF_DETAILS))
+    {
+      location_t loc;
+      loc = gimple_location (bi_call);
+      fprintf (dump_file,
+               "%s:%d: note: function call is shrink-wrapped"
+               " into error conditions.\n",
+               LOCATION_FILE (loc), LOCATION_LINE (loc));
+    }
+
+  return true;
+}
+
+/* The top level function for conditional dead code shrink
+   wrapping transformation.  */
+
+static bool
+shrink_wrap_conditional_dead_built_in_calls (vec<gimple> calls)
+{
+  bool changed = false;
+  unsigned i = 0;
+
+  unsigned n = calls.length ();
+  if (n == 0)
+    return false;
+
+  for (; i < n ; i++)
+    {
+      gimple bi_call = calls[i];
+      changed |= shrink_wrap_one_built_in_call (bi_call);
+    }
+
+  return changed;
+}
+
+/* Pass entry points.  */
+
+static unsigned int
+tree_call_cdce (void)
+{
+  basic_block bb;
+  gimple_stmt_iterator i;
+  bool something_changed = false;
+  auto_vec<gimple> cond_dead_built_in_calls;
+  FOR_EACH_BB_FN (bb, cfun)
+    {
+      /* Collect dead call candidates.  */
+      for (i = gsi_start_bb (bb); !gsi_end_p (i); gsi_next (&i))
+        {
+	  gimple stmt = gsi_stmt (i);
+          if (is_gimple_call (stmt)
+              && is_call_dce_candidate (stmt))
+            {
+              if (dump_file && (dump_flags & TDF_DETAILS))
+                {
+                  fprintf (dump_file, "Found conditional dead call: ");
+                  print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
+                  fprintf (dump_file, "\n");
+                }
+	      if (!cond_dead_built_in_calls.exists ())
+		cond_dead_built_in_calls.create (64);
+	      cond_dead_built_in_calls.safe_push (stmt);
+            }
+	}
+    }
+
+  if (!cond_dead_built_in_calls.exists ())
+    return 0;
+
+  something_changed
+    = shrink_wrap_conditional_dead_built_in_calls (cond_dead_built_in_calls);
+
+  if (something_changed)
+    {
+      free_dominance_info (CDI_DOMINATORS);
+      free_dominance_info (CDI_POST_DOMINATORS);
+      /* As we introduced new control-flow we need to insert PHI-nodes
+         for the call-clobbers of the remaining call.  */
+      mark_virtual_operands_for_renaming (cfun);
+      return TODO_update_ssa;
+    }
+
+  return 0;
+}
+
+static bool
+gate_call_cdce (void)
+{
+  /* The limit constants used in the implementation
+     assume IEEE floating point format.  Other formats
+     can be supported in the future if needed.  */
+  return flag_tree_builtin_call_dce != 0 && optimize_function_for_speed_p (cfun);
+}
+
+namespace {
+
+const pass_data pass_data_call_cdce =
+{
+  GIMPLE_PASS, /* type */
+  "cdce", /* name */
+  OPTGROUP_NONE, /* optinfo_flags */
+  true, /* has_gate */
+  true, /* has_execute */
+  TV_TREE_CALL_CDCE, /* tv_id */
+  ( PROP_cfg | PROP_ssa ), /* properties_required */
+  0, /* properties_provided */
+  0, /* properties_destroyed */
+  0, /* todo_flags_start */
+  TODO_verify_ssa, /* todo_flags_finish */
+};
+
+class pass_call_cdce : public gimple_opt_pass
+{
+public:
+  pass_call_cdce (gcc::context *ctxt)
+    : gimple_opt_pass (pass_data_call_cdce, ctxt)
+  {}
+
+  /* opt_pass methods: */
+  bool gate () { return gate_call_cdce (); }
+  unsigned int execute () { return tree_call_cdce (); }
+
+}; // class pass_call_cdce
+
+} // anon namespace
+
+gimple_opt_pass *
+make_pass_call_cdce (gcc::context *ctxt)
+{
+  return new pass_call_cdce (ctxt);
+}