CbC/CbC_gcc: gcc/tree-ssa-forwprop.c comparison

comparison gcc/tree-ssa-forwprop.c @ 0:a06113de4d67

first commit

author	kent <kent@cr.ie.u-ryukyu.ac.jp>
date	Fri, 17 Jul 2009 14:47:48 +0900
parents
children	58ad6c70ea60

comparison

equal deleted inserted replaced

--1:000000000000
+:a06113de4d67
+/* Forward propagation of expressions for single use variables.
+Copyright (C) 2004, 2005, 2007, 2008, 2009 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 "tm.h"
+#include "ggc.h"
+#include "tree.h"
+#include "rtl.h"
+#include "tm_p.h"
+#include "basic-block.h"
+#include "timevar.h"
+#include "diagnostic.h"
+#include "tree-flow.h"
+#include "tree-pass.h"
+#include "tree-dump.h"
+#include "langhooks.h"
+#include "flags.h"
+#include "gimple.h"
+/* This pass propagates the RHS of assignment statements into use
+sites of the LHS of the assignment.  It's basically a specialized
+form of tree combination.   It is hoped all of this can disappear
+when we have a generalized tree combiner.
+One class of common cases we handle is forward propagating a single use
+variable into a COND_EXPR.
+bb0:
+x = a COND b;
+if (x) goto ... else goto ...
+Will be transformed into:
+bb0:
+if (a COND b) goto ... else goto ...
+Similarly for the tests (x == 0), (x != 0), (x == 1) and (x != 1).
+Or (assuming c1 and c2 are constants):
+bb0:
+x = a + c1;
+if (x EQ/NEQ c2) goto ... else goto ...
+Will be transformed into:
+bb0:
+if (a EQ/NEQ (c2 - c1)) goto ... else goto ...
+Similarly for x = a - c1.
+Or
+bb0:
+x = !a
+if (x) goto ... else goto ...
+Will be transformed into:
+bb0:
+if (a == 0) goto ... else goto ...
+Similarly for the tests (x == 0), (x != 0), (x == 1) and (x != 1).
+For these cases, we propagate A into all, possibly more than one,
+COND_EXPRs that use X.
+Or
+bb0:
+x = (typecast) a
+if (x) goto ... else goto ...
+Will be transformed into:
+bb0:
+if (a != 0) goto ... else goto ...
+(Assuming a is an integral type and x is a boolean or x is an
+integral and a is a boolean.)
+Similarly for the tests (x == 0), (x != 0), (x == 1) and (x != 1).
+For these cases, we propagate A into all, possibly more than one,
+COND_EXPRs that use X.
+In addition to eliminating the variable and the statement which assigns
+a value to the variable, we may be able to later thread the jump without
+adding insane complexity in the dominator optimizer.
+Also note these transformations can cascade.  We handle this by having
+a worklist of COND_EXPR statements to examine.  As we make a change to
+a statement, we put it back on the worklist to examine on the next
+iteration of the main loop.
+A second class of propagation opportunities arises for ADDR_EXPR
+nodes.
+ptr = &x->y->z;
+res = *ptr;
+Will get turned into
+res = x->y->z;
+Or
+ptr = (type1*)&type2var;
+res = *ptr
+Will get turned into (if type1 and type2 are the same size
+and neither have volatile on them):
+res = VIEW_CONVERT_EXPR<type1>(type2var)
+Or
+ptr = &x[0];
+ptr2 = ptr + <constant>;
+Will get turned into
+ptr2 = &x[constant/elementsize];
+Or
+ptr = &x[0];
+offset = index * element_size;
+offset_p = (pointer) offset;
+ptr2 = ptr + offset_p
+Will get turned into:
+ptr2 = &x[index];
+We also propagate casts into SWITCH_EXPR and COND_EXPR conditions to
+allow us to remove the cast and {NOT_EXPR,NEG_EXPR} into a subsequent
+{NOT_EXPR,NEG_EXPR}.
+This will (of course) be extended as other needs arise.  */
+static bool forward_propagate_addr_expr (tree name, tree rhs);
+/* Set to true if we delete EH edges during the optimization.  */
+static bool cfg_changed;
+static tree rhs_to_tree (tree type, gimple stmt);
+/* Get the next statement we can propagate NAME's value into skipping
+trivial copies.  Returns the statement that is suitable as a
+propagation destination or NULL_TREE if there is no such one.
+This only returns destinations in a single-use chain.  FINAL_NAME_P
+if non-NULL is written to the ssa name that represents the use.  */
+static gimple
+get_prop_dest_stmt (tree name, tree *final_name_p)
+{
+use_operand_p use;
+gimple use_stmt;
+do {
+/* If name has multiple uses, bail out.  */
+if (!single_imm_use (name, &use, &use_stmt))
+return NULL;
+/* If this is not a trivial copy, we found it.  */
+if (!gimple_assign_copy_p (use_stmt)
+	|| TREE_CODE (gimple_assign_lhs (use_stmt)) != SSA_NAME
+	|| gimple_assign_rhs1 (use_stmt) != name)
+break;
+/* Continue searching uses of the copy destination.  */
+name = gimple_assign_lhs (use_stmt);
+} while (1);
+if (final_name_p)
+*final_name_p = name;
+return use_stmt;
+}
+/* Get the statement we can propagate from into NAME skipping
+trivial copies.  Returns the statement which defines the
+propagation source or NULL_TREE if there is no such one.
+If SINGLE_USE_ONLY is set considers only sources which have
+a single use chain up to NAME.  If SINGLE_USE_P is non-null,
+it is set to whether the chain to NAME is a single use chain
+or not.  SINGLE_USE_P is not written to if SINGLE_USE_ONLY is set.  */
+static gimple
+get_prop_source_stmt (tree name, bool single_use_only, bool *single_use_p)
+{
+bool single_use = true;
+do {
+gimple def_stmt = SSA_NAME_DEF_STMT (name);
+if (!has_single_use (name))
+{
+	single_use = false;
+	if (single_use_only)
+	  return NULL;
+}
+/* If name is defined by a PHI node or is the default def, bail out.  */
+if (gimple_code (def_stmt) != GIMPLE_ASSIGN)
+return NULL;
+/* If name is not a simple copy destination, we found it.  */
+if (!gimple_assign_copy_p (def_stmt)
+|| TREE_CODE (gimple_assign_rhs1 (def_stmt)) != SSA_NAME)
+{
+	tree rhs;
+	if (!single_use_only && single_use_p)
+	  *single_use_p = single_use;
+	/* We can look through pointer conversions in the search
+	   for a useful stmt for the comparison folding.  */
+	rhs = gimple_assign_rhs1 (def_stmt);
+	if (CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (def_stmt))
+	    && TREE_CODE (rhs) == SSA_NAME
+	    && POINTER_TYPE_P (TREE_TYPE (gimple_assign_lhs (def_stmt)))
+	    && POINTER_TYPE_P (TREE_TYPE (rhs)))
+	  name = rhs;
+	else
+	  return def_stmt;
+}
+else
+{
+	/* Continue searching the def of the copy source name.  */
+	name = gimple_assign_rhs1 (def_stmt);
+}
+} while (1);
+}
+/* Checks if the destination ssa name in DEF_STMT can be used as
+propagation source.  Returns true if so, otherwise false.  */
+static bool
+can_propagate_from (gimple def_stmt)
+{
+use_operand_p use_p;
+ssa_op_iter iter;
+gcc_assert (is_gimple_assign (def_stmt));
+/* If the rhs has side-effects we cannot propagate from it.  */
+if (gimple_has_volatile_ops (def_stmt))
+return false;
+/* If the rhs is a load we cannot propagate from it.  */
+if (TREE_CODE_CLASS (gimple_assign_rhs_code (def_stmt)) == tcc_reference
+|| TREE_CODE_CLASS (gimple_assign_rhs_code (def_stmt)) == tcc_declaration)
+return false;
+/* Constants can be always propagated.  */
+if (is_gimple_min_invariant
+(rhs_to_tree (TREE_TYPE (gimple_assign_lhs (def_stmt)), def_stmt)))
+return true;
+/* We cannot propagate ssa names that occur in abnormal phi nodes.  */
+FOR_EACH_SSA_USE_OPERAND (use_p, def_stmt, iter, SSA_OP_USE)
+if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (USE_FROM_PTR (use_p)))
+return false;
+/* If the definition is a conversion of a pointer to a function type,
+then we can not apply optimizations as some targets require
+function pointers to be canonicalized and in this case this
+optimization could eliminate a necessary canonicalization.  */
+if (is_gimple_assign (def_stmt)
+&& (CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (def_stmt))))
+{
+tree rhs = gimple_assign_rhs1 (def_stmt);
+if (POINTER_TYPE_P (TREE_TYPE (rhs))
+&& TREE_CODE (TREE_TYPE (TREE_TYPE (rhs))) == FUNCTION_TYPE)
+return false;
+}
+return true;
+}
+/* Remove a copy chain ending in NAME along the defs but not
+further or including UP_TO_STMT.  If NAME was replaced in
+its only use then this function can be used to clean up
+dead stmts.  Returns true if UP_TO_STMT can be removed
+as well, otherwise false.  */
+static bool
+remove_prop_source_from_use (tree name, gimple up_to_stmt)
+{
+gimple_stmt_iterator gsi;
+gimple stmt;
+do {
+if (!has_zero_uses (name))
+return false;
+stmt = SSA_NAME_DEF_STMT (name);
+if (stmt == up_to_stmt)
+return true;
+gsi = gsi_for_stmt (stmt);
+release_defs (stmt);
+gsi_remove (&gsi, true);
+name = (gimple_assign_copy_p (stmt)) ? gimple_assign_rhs1 (stmt) : NULL;
+} while (name && TREE_CODE (name) == SSA_NAME);
+return false;
+}
+/* Return the rhs of a gimple_assign STMT in a form of a single tree,
+converted to type TYPE.
+This should disappear, but is needed so we can combine expressions and use
+the fold() interfaces. Long term, we need to develop folding and combine
+routines that deal with gimple exclusively . */
+static tree
+rhs_to_tree (tree type, gimple stmt)
+{
+enum tree_code code = gimple_assign_rhs_code (stmt);
+if (get_gimple_rhs_class (code) == GIMPLE_BINARY_RHS)
+return fold_build2 (code, type, gimple_assign_rhs1 (stmt),
+			gimple_assign_rhs2 (stmt));
+else if (get_gimple_rhs_class (code) == GIMPLE_UNARY_RHS)
+return build1 (code, type, gimple_assign_rhs1 (stmt));
+else if (get_gimple_rhs_class (code) == GIMPLE_SINGLE_RHS)
+return gimple_assign_rhs1 (stmt);
+else
+gcc_unreachable ();
+}
+/* Combine OP0 CODE OP1 in the context of a COND_EXPR.  Returns
+the folded result in a form suitable for COND_EXPR_COND or
+NULL_TREE, if there is no suitable simplified form.  If
+INVARIANT_ONLY is true only gimple_min_invariant results are
+considered simplified.  */
+static tree
+combine_cond_expr_cond (enum tree_code code, tree type,
+			tree op0, tree op1, bool invariant_only)
+{
+tree t;
+gcc_assert (TREE_CODE_CLASS (code) == tcc_comparison);
+t = fold_binary (code, type, op0, op1);
+if (!t)
+return NULL_TREE;
+/* Require that we got a boolean type out if we put one in.  */
+gcc_assert (TREE_CODE (TREE_TYPE (t)) == TREE_CODE (type));
+/* Canonicalize the combined condition for use in a COND_EXPR.  */
+t = canonicalize_cond_expr_cond (t);
+/* Bail out if we required an invariant but didn't get one.  */
+if (!t || (invariant_only && !is_gimple_min_invariant (t)))
+return NULL_TREE;
+return t;
+}
+/* Propagate from the ssa name definition statements of COND_EXPR
+in GIMPLE_COND statement STMT into the conditional if that simplifies it.
+Returns zero if no statement was changed, one if there were
+changes and two if cfg_cleanup needs to run.
+This must be kept in sync with forward_propagate_into_cond.  */
+static int
+forward_propagate_into_gimple_cond (gimple stmt)
+{
+int did_something = 0;
+do {
+tree tmp = NULL_TREE;
+tree name, rhs0 = NULL_TREE, rhs1 = NULL_TREE;
+gimple def_stmt;
+bool single_use0_p = false, single_use1_p = false;
+enum tree_code code = gimple_cond_code (stmt);
+/* We can do tree combining on SSA_NAME and comparison expressions.  */
+if (TREE_CODE_CLASS (gimple_cond_code (stmt)) == tcc_comparison
+&& TREE_CODE (gimple_cond_lhs (stmt)) == SSA_NAME)
+{
+	/* For comparisons use the first operand, that is likely to
+	   simplify comparisons against constants.  */
+	name = gimple_cond_lhs (stmt);
+	def_stmt = get_prop_source_stmt (name, false, &single_use0_p);
+	if (def_stmt && can_propagate_from (def_stmt))
+	  {
+	    tree op1 = gimple_cond_rhs (stmt);
+	    rhs0 = rhs_to_tree (TREE_TYPE (op1), def_stmt);
+	    tmp = combine_cond_expr_cond (code, boolean_type_node, rhs0,
+					  op1, !single_use0_p);
+	  }
+	/* If that wasn't successful, try the second operand.  */
+	if (tmp == NULL_TREE
+	    && TREE_CODE (gimple_cond_rhs (stmt)) == SSA_NAME)
+	  {
+	    tree op0 = gimple_cond_lhs (stmt);
+	    name = gimple_cond_rhs (stmt);
+	    def_stmt = get_prop_source_stmt (name, false, &single_use1_p);
+	    if (!def_stmt || !can_propagate_from (def_stmt))
+	      return did_something;
+	    rhs1 = rhs_to_tree (TREE_TYPE (op0), def_stmt);
+	    tmp = combine_cond_expr_cond (code, boolean_type_node, op0, rhs1,
+					  !single_use1_p);
+	  }
+	/* If that wasn't successful either, try both operands.  */
+	if (tmp == NULL_TREE
+	    && rhs0 != NULL_TREE
+	    && rhs1 != NULL_TREE)
+	  tmp = combine_cond_expr_cond (code, boolean_type_node, rhs0,
+					fold_convert (TREE_TYPE (rhs0), rhs1),
+					!(single_use0_p && single_use1_p));
+}
+if (tmp)
+{
+	if (dump_file && tmp)
+	  {
+tree cond = build2 (gimple_cond_code (stmt),
+				boolean_type_node,
+				gimple_cond_lhs (stmt),
+				gimple_cond_rhs (stmt));
+	    fprintf (dump_file, "  Replaced '");
+	    print_generic_expr (dump_file, cond, 0);
+	    fprintf (dump_file, "' with '");
+	    print_generic_expr (dump_file, tmp, 0);
+	    fprintf (dump_file, "'\n");
+	  }
+gimple_cond_set_condition_from_tree (stmt, unshare_expr (tmp));
+	update_stmt (stmt);
+	/* Remove defining statements.  */
+	remove_prop_source_from_use (name, NULL);
+	if (is_gimple_min_invariant (tmp))
+	  did_something = 2;
+	else if (did_something == 0)
+	  did_something = 1;
+	/* Continue combining.  */
+	continue;
+}
+break;
+} while (1);
+return did_something;
+}
+/* Propagate from the ssa name definition statements of COND_EXPR
+in the rhs of statement STMT into the conditional if that simplifies it.
+Returns zero if no statement was changed, one if there were
+changes and two if cfg_cleanup needs to run.
+This must be kept in sync with forward_propagate_into_gimple_cond.  */
+static int
+forward_propagate_into_cond (gimple_stmt_iterator *gsi_p)
+{
+gimple stmt = gsi_stmt (*gsi_p);
+int did_something = 0;
+do {
+tree tmp = NULL_TREE;
+tree cond = gimple_assign_rhs1 (stmt);
+tree name, rhs0 = NULL_TREE, rhs1 = NULL_TREE;
+gimple def_stmt;
+bool single_use0_p = false, single_use1_p = false;
+/* We can do tree combining on SSA_NAME and comparison expressions.  */
+if (COMPARISON_CLASS_P (cond)
+	&& TREE_CODE (TREE_OPERAND (cond, 0)) == SSA_NAME)
+{
+	/* For comparisons use the first operand, that is likely to
+	   simplify comparisons against constants.  */
+	name = TREE_OPERAND (cond, 0);
+	def_stmt = get_prop_source_stmt (name, false, &single_use0_p);
+	if (def_stmt && can_propagate_from (def_stmt))
+	  {
+	    tree op1 = TREE_OPERAND (cond, 1);
+	    rhs0 = rhs_to_tree (TREE_TYPE (op1), def_stmt);
+	    tmp = combine_cond_expr_cond (TREE_CODE (cond), boolean_type_node,
+					  rhs0, op1, !single_use0_p);
+	  }
+	/* If that wasn't successful, try the second operand.  */
+	if (tmp == NULL_TREE
+	    && TREE_CODE (TREE_OPERAND (cond, 1)) == SSA_NAME)
+	  {
+	    tree op0 = TREE_OPERAND (cond, 0);
+	    name = TREE_OPERAND (cond, 1);
+	    def_stmt = get_prop_source_stmt (name, false, &single_use1_p);
+	    if (!def_stmt || !can_propagate_from (def_stmt))
+	      return did_something;
+	    rhs1 = rhs_to_tree (TREE_TYPE (op0), def_stmt);
+	    tmp = combine_cond_expr_cond (TREE_CODE (cond), boolean_type_node,
+					  op0, rhs1, !single_use1_p);
+	  }
+	/* If that wasn't successful either, try both operands.  */
+	if (tmp == NULL_TREE
+	    && rhs0 != NULL_TREE
+	    && rhs1 != NULL_TREE)
+	  tmp = combine_cond_expr_cond (TREE_CODE (cond), boolean_type_node,
+					rhs0, fold_convert (TREE_TYPE (rhs0),
+							    rhs1),
+					!(single_use0_p && single_use1_p));
+}
+else if (TREE_CODE (cond) == SSA_NAME)
+{
+	name = cond;
+	def_stmt = get_prop_source_stmt (name, true, NULL);
+	if (def_stmt || !can_propagate_from (def_stmt))
+	  return did_something;
+	rhs0 = gimple_assign_rhs1 (def_stmt);
+	tmp = combine_cond_expr_cond (NE_EXPR, boolean_type_node, rhs0,
+				      build_int_cst (TREE_TYPE (rhs0), 0),
+				      false);
+}
+if (tmp)
+{
+	if (dump_file && tmp)
+	  {
+	    fprintf (dump_file, "  Replaced '");
+	    print_generic_expr (dump_file, cond, 0);
+	    fprintf (dump_file, "' with '");
+	    print_generic_expr (dump_file, tmp, 0);
+	    fprintf (dump_file, "'\n");
+	  }
+	gimple_assign_set_rhs_from_tree (gsi_p, unshare_expr (tmp));
+	stmt = gsi_stmt (*gsi_p);
+	update_stmt (stmt);
+	/* Remove defining statements.  */
+	remove_prop_source_from_use (name, NULL);
+	if (is_gimple_min_invariant (tmp))
+	  did_something = 2;
+	else if (did_something == 0)
+	  did_something = 1;
+	/* Continue combining.  */
+	continue;
+}
+break;
+} while (1);
+return did_something;
+}
+/* We've just substituted an ADDR_EXPR into stmt.  Update all the
+relevant data structures to match.  */
+static void
+tidy_after_forward_propagate_addr (gimple stmt)
+{
+/* We may have turned a trapping insn into a non-trapping insn.  */
+if (maybe_clean_or_replace_eh_stmt (stmt, stmt)
+&& gimple_purge_dead_eh_edges (gimple_bb (stmt)))
+cfg_changed = true;
+if (TREE_CODE (gimple_assign_rhs1 (stmt)) == ADDR_EXPR)
+recompute_tree_invariant_for_addr_expr (gimple_assign_rhs1 (stmt));
+mark_symbols_for_renaming (stmt);
+}
+/* DEF_RHS contains the address of the 0th element in an array.
+USE_STMT uses type of DEF_RHS to compute the address of an
+arbitrary element within the array.  The (variable) byte offset
+of the element is contained in OFFSET.
+We walk back through the use-def chains of OFFSET to verify that
+it is indeed computing the offset of an element within the array
+and extract the index corresponding to the given byte offset.
+We then try to fold the entire address expression into a form
+&array[index].
+If we are successful, we replace the right hand side of USE_STMT
+with the new address computation.  */
+static bool
+forward_propagate_addr_into_variable_array_index (tree offset,
+						  tree def_rhs,
+						  gimple_stmt_iterator *use_stmt_gsi)
+{
+tree index;
+gimple offset_def, use_stmt = gsi_stmt (*use_stmt_gsi);
+/* Get the offset's defining statement.  */
+offset_def = SSA_NAME_DEF_STMT (offset);
+/* Try to find an expression for a proper index.  This is either a
+multiplication expression by the element size or just the ssa name we came
+along in case the element size is one. In that case, however, we do not
+allow multiplications because they can be computing index to a higher
+level dimension (PR 37861). */
+if (integer_onep (TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (def_rhs)))))
+{
+if (is_gimple_assign (offset_def)
+	  && gimple_assign_rhs_code (offset_def) == MULT_EXPR)
+	return false;
+index = offset;
+}
+else
+{
+/* The statement which defines OFFSET before type conversion
+must be a simple GIMPLE_ASSIGN.  */
+if (!is_gimple_assign (offset_def))
+	return false;
+/* The RHS of the statement which defines OFFSET must be a
+	 multiplication of an object by the size of the array elements.
+	 This implicitly verifies that the size of the array elements
+	 is constant.  */
+offset = gimple_assign_rhs1 (offset_def);
+if (gimple_assign_rhs_code (offset_def) != MULT_EXPR
+	 || TREE_CODE (gimple_assign_rhs2 (offset_def)) != INTEGER_CST
+	 || !simple_cst_equal (gimple_assign_rhs2 (offset_def),
+			       TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (def_rhs)))))
+	return false;
+/* The first operand to the MULT_EXPR is the desired index.  */
+index = offset;
+}
+/* Replace the pointer addition with array indexing.  */
+gimple_assign_set_rhs_from_tree (use_stmt_gsi, unshare_expr (def_rhs));
+use_stmt = gsi_stmt (*use_stmt_gsi);
+TREE_OPERAND (TREE_OPERAND (gimple_assign_rhs1 (use_stmt), 0), 1)
+= index;
+/* That should have created gimple, so there is no need to
+record information to undo the propagation.  */
+fold_stmt_inplace (use_stmt);
+tidy_after_forward_propagate_addr (use_stmt);
+return true;
+}
+/* NAME is a SSA_NAME representing DEF_RHS which is of the form
+ADDR_EXPR <whatever>.
+Try to forward propagate the ADDR_EXPR into the use USE_STMT.
+Often this will allow for removal of an ADDR_EXPR and INDIRECT_REF
+node or for recovery of array indexing from pointer arithmetic.
+Return true if the propagation was successful (the propagation can
+be not totally successful, yet things may have been changed).  */
+static bool
+forward_propagate_addr_expr_1 (tree name, tree def_rhs,
+			       gimple_stmt_iterator *use_stmt_gsi,
+			       bool single_use_p)
+{
+tree lhs, rhs, rhs2, array_ref;
+tree *rhsp, *lhsp;
+gimple use_stmt = gsi_stmt (*use_stmt_gsi);
+enum tree_code rhs_code;
+gcc_assert (TREE_CODE (def_rhs) == ADDR_EXPR);
+lhs = gimple_assign_lhs (use_stmt);
+rhs_code = gimple_assign_rhs_code (use_stmt);
+rhs = gimple_assign_rhs1 (use_stmt);
+/* Trivial cases.  The use statement could be a trivial copy or a
+useless conversion.  Recurse to the uses of the lhs as copyprop does
+not copy through different variant pointers and FRE does not catch
+all useless conversions.  Treat the case of a single-use name and
+a conversion to def_rhs type separate, though.  */
+if (TREE_CODE (lhs) == SSA_NAME
+&& ((rhs_code == SSA_NAME && rhs == name)
+	  || CONVERT_EXPR_CODE_P (rhs_code)))
+{
+/* Only recurse if we don't deal with a single use or we cannot
+	 do the propagation to the current statement.  In particular
+	 we can end up with a conversion needed for a non-invariant
+	 address which we cannot do in a single statement.  */
+if (!single_use_p
+	  || (!useless_type_conversion_p (TREE_TYPE (lhs), TREE_TYPE (def_rhs))
+	      && !is_gimple_min_invariant (def_rhs)))
+	return forward_propagate_addr_expr (lhs, def_rhs);
+gimple_assign_set_rhs1 (use_stmt, unshare_expr (def_rhs));
+if (useless_type_conversion_p (TREE_TYPE (lhs), TREE_TYPE (def_rhs)))
+	gimple_assign_set_rhs_code (use_stmt, TREE_CODE (def_rhs));
+else
+	gimple_assign_set_rhs_code (use_stmt, NOP_EXPR);
+return true;
+}
+/* Now strip away any outer COMPONENT_REF/ARRAY_REF nodes from the LHS.
+ADDR_EXPR will not appear on the LHS.  */
+lhsp = gimple_assign_lhs_ptr (use_stmt);
+while (handled_component_p (*lhsp))
+lhsp = &TREE_OPERAND (*lhsp, 0);
+lhs = *lhsp;
+/* Now see if the LHS node is an INDIRECT_REF using NAME.  If so,
+propagate the ADDR_EXPR into the use of NAME and fold the result.  */
+if (TREE_CODE (lhs) == INDIRECT_REF
+&& TREE_OPERAND (lhs, 0) == name
+&& may_propagate_address_into_dereference (def_rhs, lhs)
+&& (lhsp != gimple_assign_lhs_ptr (use_stmt)
+	  || useless_type_conversion_p (TREE_TYPE (TREE_OPERAND (def_rhs, 0)),
+					TREE_TYPE (rhs))))
+{
+*lhsp = unshare_expr (TREE_OPERAND (def_rhs, 0));
+fold_stmt_inplace (use_stmt);
+tidy_after_forward_propagate_addr (use_stmt);
+/* Continue propagating into the RHS if this was not the only use.  */
+if (single_use_p)
+	return true;
+}
+/* Strip away any outer COMPONENT_REF, ARRAY_REF or ADDR_EXPR
+nodes from the RHS.  */
+rhsp = gimple_assign_rhs1_ptr (use_stmt);
+while (handled_component_p (*rhsp)
+	 || TREE_CODE (*rhsp) == ADDR_EXPR)
+rhsp = &TREE_OPERAND (*rhsp, 0);
+rhs = *rhsp;
+/* Now see if the RHS node is an INDIRECT_REF using NAME.  If so,
+propagate the ADDR_EXPR into the use of NAME and fold the result.  */
+if (TREE_CODE (rhs) == INDIRECT_REF
+&& TREE_OPERAND (rhs, 0) == name
+&& may_propagate_address_into_dereference (def_rhs, rhs))
+{
+*rhsp = unshare_expr (TREE_OPERAND (def_rhs, 0));
+fold_stmt_inplace (use_stmt);
+tidy_after_forward_propagate_addr (use_stmt);
+return true;
+}
+/* Now see if the RHS node is an INDIRECT_REF using NAME.  If so,
+propagate the ADDR_EXPR into the use of NAME and try to
+create a VCE and fold the result.  */
+if (TREE_CODE (rhs) == INDIRECT_REF
+&& TREE_OPERAND (rhs, 0) == name
+&& TYPE_SIZE (TREE_TYPE (rhs))
+&& TYPE_SIZE (TREE_TYPE (TREE_OPERAND (def_rhs, 0)))
+/* Function decls should not be used for VCE either as it could be a
+function descriptor that we want and not the actual function code.  */
+&& TREE_CODE (TREE_OPERAND (def_rhs, 0)) != FUNCTION_DECL
+/* We should not convert volatile loads to non volatile loads. */
+&& !TYPE_VOLATILE (TREE_TYPE (rhs))
+&& !TYPE_VOLATILE (TREE_TYPE (TREE_OPERAND (def_rhs, 0)))
+&& operand_equal_p (TYPE_SIZE (TREE_TYPE (rhs)),
+			  TYPE_SIZE (TREE_TYPE (TREE_OPERAND (def_rhs, 0))), 0))
+{
+tree def_rhs_base, new_rhs = unshare_expr (TREE_OPERAND (def_rhs, 0));
+new_rhs = fold_build1 (VIEW_CONVERT_EXPR, TREE_TYPE (rhs), new_rhs);
+if (TREE_CODE (new_rhs) != VIEW_CONVERT_EXPR)
+{
+	 /* If we have folded the VIEW_CONVERT_EXPR then the result is only
+	    valid if we can replace the whole rhs of the use statement.  */
+	 if (rhs != gimple_assign_rhs1 (use_stmt))
+	   return false;
+	 new_rhs = force_gimple_operand_gsi (use_stmt_gsi, new_rhs, true, NULL,
+					     true, GSI_NEW_STMT);
+	 gimple_assign_set_rhs1 (use_stmt, new_rhs);
+	 tidy_after_forward_propagate_addr (use_stmt);
+	 return true;
+}
+/* If the defining rhs comes from an indirect reference, then do not
+convert into a VIEW_CONVERT_EXPR.  */
+def_rhs_base = TREE_OPERAND (def_rhs, 0);
+while (handled_component_p (def_rhs_base))
+def_rhs_base = TREE_OPERAND (def_rhs_base, 0);
+if (!INDIRECT_REF_P (def_rhs_base))
+{
+	 /* We may have arbitrary VIEW_CONVERT_EXPRs in a nested component
+	    reference.  Place it there and fold the thing.  */
+	 *rhsp = new_rhs;
+	 fold_stmt_inplace (use_stmt);
+	 tidy_after_forward_propagate_addr (use_stmt);
+	 return true;
+}
+}
+/* If the use of the ADDR_EXPR is not a POINTER_PLUS_EXPR, there
+is nothing to do. */
+if (gimple_assign_rhs_code (use_stmt) != POINTER_PLUS_EXPR
+|| gimple_assign_rhs1 (use_stmt) != name)
+return false;
+/* The remaining cases are all for turning pointer arithmetic into
+array indexing.  They only apply when we have the address of
+element zero in an array.  If that is not the case then there
+is nothing to do.  */
+array_ref = TREE_OPERAND (def_rhs, 0);
+if (TREE_CODE (array_ref) != ARRAY_REF
+|| TREE_CODE (TREE_TYPE (TREE_OPERAND (array_ref, 0))) != ARRAY_TYPE
+|| !integer_zerop (TREE_OPERAND (array_ref, 1)))
+return false;
+rhs2 = gimple_assign_rhs2 (use_stmt);
+/* Try to optimize &x[0] p+ C where C is a multiple of the size
+of the elements in X into &x[C/element size].  */
+if (TREE_CODE (rhs2) == INTEGER_CST)
+{
+tree new_rhs = maybe_fold_stmt_addition (gimple_expr_type (use_stmt),
+					       array_ref, rhs2);
+if (new_rhs)
+	{
+	  gimple_assign_set_rhs_from_tree (use_stmt_gsi, new_rhs);
+	  use_stmt = gsi_stmt (*use_stmt_gsi);
+	  update_stmt (use_stmt);
+	  tidy_after_forward_propagate_addr (use_stmt);
+	  return true;
+	}
+}
+/* Try to optimize &x[0] p+ OFFSET where OFFSET is defined by
+converting a multiplication of an index by the size of the
+array elements, then the result is converted into the proper
+type for the arithmetic.  */
+if (TREE_CODE (rhs2) == SSA_NAME
+&& useless_type_conversion_p (TREE_TYPE (name), TREE_TYPE (def_rhs))
+/* Avoid problems with IVopts creating PLUS_EXPRs with a
+	 different type than their operands.  */
+&& useless_type_conversion_p (TREE_TYPE (lhs), TREE_TYPE (def_rhs)))
+return forward_propagate_addr_into_variable_array_index (rhs2, def_rhs,
+							     use_stmt_gsi);
+return false;
+}
+/* STMT is a statement of the form SSA_NAME = ADDR_EXPR <whatever>.
+Try to forward propagate the ADDR_EXPR into all uses of the SSA_NAME.
+Often this will allow for removal of an ADDR_EXPR and INDIRECT_REF
+node or for recovery of array indexing from pointer arithmetic.
+Returns true, if all uses have been propagated into.  */
+static bool
+forward_propagate_addr_expr (tree name, tree rhs)
+{
+int stmt_loop_depth = gimple_bb (SSA_NAME_DEF_STMT (name))->loop_depth;
+imm_use_iterator iter;
+gimple use_stmt;
+bool all = true;
+bool single_use_p = has_single_use (name);
+FOR_EACH_IMM_USE_STMT (use_stmt, iter, name)
+{
+bool result;
+tree use_rhs;
+/* If the use is not in a simple assignment statement, then
+	 there is nothing we can do.  */
+if (gimple_code (use_stmt) != GIMPLE_ASSIGN)
+	{
+	  all = false;
+	  continue;
+	}
+/* If the use is in a deeper loop nest, then we do not want
+	 to propagate the ADDR_EXPR into the loop as that is likely
+	 adding expression evaluations into the loop.  */
+if (gimple_bb (use_stmt)->loop_depth > stmt_loop_depth)
+	{
+	  all = false;
+	  continue;
+	}
+push_stmt_changes (&use_stmt);
+{
+	gimple_stmt_iterator gsi = gsi_for_stmt (use_stmt);
+	result = forward_propagate_addr_expr_1 (name, rhs, &gsi,
+						single_use_p);
+	use_stmt = gsi_stmt (gsi);
+}
+all &= result;
+pop_stmt_changes (&use_stmt);
+/* Remove intermediate now unused copy and conversion chains.  */
+use_rhs = gimple_assign_rhs1 (use_stmt);
+if (result
+	  && TREE_CODE (gimple_assign_lhs (use_stmt)) == SSA_NAME
+	  && (TREE_CODE (use_rhs) == SSA_NAME
+	      || (CONVERT_EXPR_P (use_rhs)
+		  && TREE_CODE (TREE_OPERAND (use_rhs, 0)) == SSA_NAME)))
+	{
+	  gimple_stmt_iterator gsi = gsi_for_stmt (use_stmt);
+	  release_defs (use_stmt);
+	  gsi_remove (&gsi, true);
+	}
+}
+return all;
+}
+/* Forward propagate the comparison defined in STMT like
+cond_1 = x CMP y to uses of the form
+a_1 = (T')cond_1
+a_1 = !cond_1
+a_1 = cond_1 != 0
+Returns true if stmt is now unused.  */
+static bool
+forward_propagate_comparison (gimple stmt)
+{
+tree name = gimple_assign_lhs (stmt);
+gimple use_stmt;
+tree tmp = NULL_TREE;
+/* Don't propagate ssa names that occur in abnormal phis.  */
+if ((TREE_CODE (gimple_assign_rhs1 (stmt)) == SSA_NAME
+&& SSA_NAME_OCCURS_IN_ABNORMAL_PHI (gimple_assign_rhs1 (stmt)))
+|| (TREE_CODE (gimple_assign_rhs2 (stmt)) == SSA_NAME
+&& SSA_NAME_OCCURS_IN_ABNORMAL_PHI (gimple_assign_rhs2 (stmt))))
+return false;
+/* Do not un-cse comparisons.  But propagate through copies.  */
+use_stmt = get_prop_dest_stmt (name, &name);
+if (!use_stmt)
+return false;
+/* Conversion of the condition result to another integral type.  */
+if (is_gimple_assign (use_stmt)
+&& (CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (use_stmt))
+	  || TREE_CODE_CLASS (gimple_assign_rhs_code (use_stmt))
+	     == tcc_comparison
+|| gimple_assign_rhs_code (use_stmt) == TRUTH_NOT_EXPR)
+&& INTEGRAL_TYPE_P (TREE_TYPE (gimple_assign_lhs (use_stmt))))
+{
+tree lhs = gimple_assign_lhs (use_stmt);
+/* We can propagate the condition into a conversion.  */
+if (CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (use_stmt)))
+	{
+	  /* Avoid using fold here as that may create a COND_EXPR with
+	     non-boolean condition as canonical form.  */
+	  tmp = build2 (gimple_assign_rhs_code (stmt), TREE_TYPE (lhs),
+gimple_assign_rhs1 (stmt), gimple_assign_rhs2 (stmt));
+	}
+/* We can propagate the condition into X op CST where op
+	 is EQ_EXPR or NE_EXPR and CST is either one or zero.  */
+else if (TREE_CODE_CLASS (gimple_assign_rhs_code (use_stmt))
+== tcc_comparison
+&& TREE_CODE (gimple_assign_rhs1 (use_stmt)) == SSA_NAME
+&& TREE_CODE (gimple_assign_rhs2 (use_stmt)) == INTEGER_CST)
+{
+enum tree_code code = gimple_assign_rhs_code (use_stmt);
+tree cst = gimple_assign_rhs2 (use_stmt);
+	tree cond;
+	cond = build2 (gimple_assign_rhs_code (stmt),
+		       TREE_TYPE (cst),
+		       gimple_assign_rhs1 (stmt),
+		       gimple_assign_rhs2 (stmt));
+tmp = combine_cond_expr_cond (code, TREE_TYPE (lhs), cond, cst, false);
+if (tmp == NULL_TREE)
+return false;
+}
+/* We can propagate the condition into a statement that
+	 computes the logical negation of the comparison result.  */
+else if (gimple_assign_rhs_code (use_stmt) == TRUTH_NOT_EXPR)
+	{
+	  tree type = TREE_TYPE (gimple_assign_rhs1 (stmt));
+	  bool nans = HONOR_NANS (TYPE_MODE (type));
+	  enum tree_code code;
+	  code = invert_tree_comparison (gimple_assign_rhs_code (stmt), nans);
+	  if (code == ERROR_MARK)
+	    return false;
+	  tmp = build2 (code, TREE_TYPE (lhs), gimple_assign_rhs1 (stmt),
+gimple_assign_rhs2 (stmt));
+	}
+else
+	return false;
+{
+	gimple_stmt_iterator gsi = gsi_for_stmt (use_stmt);
+	gimple_assign_set_rhs_from_tree (&gsi, unshare_expr (tmp));
+	use_stmt = gsi_stmt (gsi);
+	update_stmt (use_stmt);
+}
+/* Remove defining statements.  */
+remove_prop_source_from_use (name, stmt);
+if (dump_file && (dump_flags & TDF_DETAILS))
+	{
+	  tree old_rhs = rhs_to_tree (TREE_TYPE (gimple_assign_lhs (stmt)),
+stmt);
+	  fprintf (dump_file, "  Replaced '");
+	  print_generic_expr (dump_file, old_rhs, dump_flags);
+	  fprintf (dump_file, "' with '");
+	  print_generic_expr (dump_file, tmp, dump_flags);
+	  fprintf (dump_file, "'\n");
+	}
+return true;
+}
+return false;
+}
+/* If we have lhs = ~x (STMT), look and see if earlier we had x = ~y.
+If so, we can change STMT into lhs = y which can later be copy
+propagated.  Similarly for negation.
+This could trivially be formulated as a forward propagation
+to immediate uses.  However, we already had an implementation
+from DOM which used backward propagation via the use-def links.
+It turns out that backward propagation is actually faster as
+there's less work to do for each NOT/NEG expression we find.
+Backwards propagation needs to look at the statement in a single
+backlink.  Forward propagation needs to look at potentially more
+than one forward link.  */
+static void
+simplify_not_neg_expr (gimple_stmt_iterator *gsi_p)
+{
+gimple stmt = gsi_stmt (*gsi_p);
+tree rhs = gimple_assign_rhs1 (stmt);
+gimple rhs_def_stmt = SSA_NAME_DEF_STMT (rhs);
+/* See if the RHS_DEF_STMT has the same form as our statement.  */
+if (is_gimple_assign (rhs_def_stmt)
+&& gimple_assign_rhs_code (rhs_def_stmt) == gimple_assign_rhs_code (stmt))
+{
+tree rhs_def_operand = gimple_assign_rhs1 (rhs_def_stmt);
+/* Verify that RHS_DEF_OPERAND is a suitable SSA_NAME.  */
+if (TREE_CODE (rhs_def_operand) == SSA_NAME
+	  && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rhs_def_operand))
+	{
+	  gimple_assign_set_rhs_from_tree (gsi_p, rhs_def_operand);
+	  stmt = gsi_stmt (*gsi_p);
+	  update_stmt (stmt);
+	}
+}
+}
+/* STMT is a SWITCH_EXPR for which we attempt to find equivalent forms of
+the condition which we may be able to optimize better.  */
+static void
+simplify_gimple_switch (gimple stmt)
+{
+tree cond = gimple_switch_index (stmt);
+tree def, to, ti;
+gimple def_stmt;
+/* The optimization that we really care about is removing unnecessary
+casts.  That will let us do much better in propagating the inferred
+constant at the switch target.  */
+if (TREE_CODE (cond) == SSA_NAME)
+{
+def_stmt = SSA_NAME_DEF_STMT (cond);
+if (is_gimple_assign (def_stmt))
+	{
+	  if (gimple_assign_rhs_code (def_stmt) == NOP_EXPR)
+	    {
+	      int need_precision;
+	      bool fail;
+	      def = gimple_assign_rhs1 (def_stmt);
+#ifdef ENABLE_CHECKING
+	      /* ??? Why was Jeff testing this?  We are gimple...  */
+	      gcc_assert (is_gimple_val (def));
+#endif
+	      to = TREE_TYPE (cond);
+	      ti = TREE_TYPE (def);
+	      /* If we have an extension that preserves value, then we
+		 can copy the source value into the switch.  */
+	      need_precision = TYPE_PRECISION (ti);
+	      fail = false;
+	      if (! INTEGRAL_TYPE_P (ti))
+		fail = true;
+	      else if (TYPE_UNSIGNED (to) && !TYPE_UNSIGNED (ti))
+		fail = true;
+	      else if (!TYPE_UNSIGNED (to) && TYPE_UNSIGNED (ti))
+		need_precision += 1;
+	      if (TYPE_PRECISION (to) < need_precision)
+		fail = true;
+	      if (!fail)
+		{
+		  gimple_switch_set_index (stmt, def);
+		  update_stmt (stmt);
+		}
+	    }
+	}
+}
+}
+/* Main entry point for the forward propagation optimizer.  */
+static unsigned int
+tree_ssa_forward_propagate_single_use_vars (void)
+{
+basic_block bb;
+unsigned int todoflags = 0;
+cfg_changed = false;
+FOR_EACH_BB (bb)
+{
+gimple_stmt_iterator gsi;
+/* Note we update GSI within the loop as necessary.  */
+for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); )
+	{
+	  gimple stmt = gsi_stmt (gsi);
+	  /* If this statement sets an SSA_NAME to an address,
+	     try to propagate the address into the uses of the SSA_NAME.  */
+	  if (is_gimple_assign (stmt))
+	    {
+	      tree lhs = gimple_assign_lhs (stmt);
+	      tree rhs = gimple_assign_rhs1 (stmt);
+	      if (TREE_CODE (lhs) != SSA_NAME)
+		{
+		  gsi_next (&gsi);
+		  continue;
+		}
+	      if (gimple_assign_rhs_code (stmt) == ADDR_EXPR
+		  /* Handle pointer conversions on invariant addresses
+		     as well, as this is valid gimple.  */
+		  || (CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (stmt))
+		      && TREE_CODE (rhs) == ADDR_EXPR
+		      && POINTER_TYPE_P (TREE_TYPE (lhs))))
+		{
+		  STRIP_NOPS (rhs);
+		  if (!stmt_references_abnormal_ssa_name (stmt)
+		      && forward_propagate_addr_expr (lhs, rhs))
+		    {
+		      release_defs (stmt);
+		      todoflags |= TODO_remove_unused_locals;
+		      gsi_remove (&gsi, true);
+		    }
+		  else
+		    gsi_next (&gsi);
+		}
+	      else if ((gimple_assign_rhs_code (stmt) == BIT_NOT_EXPR
+		        || gimple_assign_rhs_code (stmt) == NEGATE_EXPR)
+		       && TREE_CODE (rhs) == SSA_NAME)
+		{
+		  simplify_not_neg_expr (&gsi);
+		  gsi_next (&gsi);
+		}
+	      else if (gimple_assign_rhs_code (stmt) == COND_EXPR)
+{
+/* In this case the entire COND_EXPR is in rhs1. */
+		  int did_something;
+		  fold_defer_overflow_warnings ();
+did_something = forward_propagate_into_cond (&gsi);
+		  stmt = gsi_stmt (gsi);
+		  if (did_something == 2)
+		    cfg_changed = true;
+		  fold_undefer_overflow_warnings (!TREE_NO_WARNING (rhs)
+		    && did_something, stmt, WARN_STRICT_OVERFLOW_CONDITIONAL);
+		  gsi_next (&gsi);
+}
+	      else if (TREE_CODE_CLASS (gimple_assign_rhs_code (stmt))
+					== tcc_comparison)
+		{
+		  if (forward_propagate_comparison (stmt))
+		    {
+		      release_defs (stmt);
+		      todoflags |= TODO_remove_unused_locals;
+		      gsi_remove (&gsi, true);
+		    }
+		  else
+		    gsi_next (&gsi);
+		}
+	      else
+		gsi_next (&gsi);
+	    }
+	  else if (gimple_code (stmt) == GIMPLE_SWITCH)
+	    {
+	      simplify_gimple_switch (stmt);
+	      gsi_next (&gsi);
+	    }
+	  else if (gimple_code (stmt) == GIMPLE_COND)
+	    {
+	      int did_something;
+	      fold_defer_overflow_warnings ();
+	      did_something = forward_propagate_into_gimple_cond (stmt);
+	      if (did_something == 2)
+		cfg_changed = true;
+	      fold_undefer_overflow_warnings (did_something, stmt,
+					      WARN_STRICT_OVERFLOW_CONDITIONAL);
+	      gsi_next (&gsi);
+	    }
+	  else
+	    gsi_next (&gsi);
+	}
+}
+if (cfg_changed)
+todoflags |= TODO_cleanup_cfg;
+return todoflags;
+}
+static bool
+gate_forwprop (void)
+{
+return 1;
+}
+struct gimple_opt_pass pass_forwprop =
+{
+{
+GIMPLE_PASS,
+"forwprop",			/* name */
+gate_forwprop,		/* gate */
+tree_ssa_forward_propagate_single_use_vars,	/* execute */
+NULL,				/* sub */
+NULL,				/* next */
+0,				/* static_pass_number */
+TV_TREE_FORWPROP,		/* tv_id */
+PROP_cfg | PROP_ssa,		/* properties_required */
+0,				/* properties_provided */
+0,				/* properties_destroyed */
+0,				/* todo_flags_start */
+TODO_dump_func
+| TODO_ggc_collect
+| TODO_update_ssa
+| TODO_verify_ssa		/* todo_flags_finish */
+}
+};

Mercurial > hg > CbC > CbC_gcc

comparison gcc/tree-ssa-forwprop.c @ 0:a06113de4d67