545 lines
15 KiB
C
545 lines
15 KiB
C
/* Tree lowering pass. This pass gimplifies the tree representation built
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by the C-based front ends. The structure of gimplified, or
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language-independent, trees is dictated by the grammar described in this
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file.
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Copyright (C) 2002, 2003, 2004 Free Software Foundation, Inc.
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Lowering of expressions contributed by Sebastian Pop <s.pop@laposte.net>
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Re-written to support lowering of whole function trees, documentation
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and miscellaneous cleanups by Diego Novillo <dnovillo@redhat.com>
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This file is part of GCC.
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GCC is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free
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Software Foundation; either version 2, or (at your option) any later
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version.
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GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with GCC; see the file COPYING. If not, write to the Free
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Software Foundation, 59 Temple Place - Suite 330, Boston, MA
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02111-1307, USA. */
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#include "config.h"
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#include "system.h"
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#include "coretypes.h"
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#include "tm.h"
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#include "tree.h"
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#include "errors.h"
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#include "varray.h"
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#include "c-tree.h"
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#include "c-common.h"
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#include "tree-gimple.h"
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#include "hard-reg-set.h"
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#include "basic-block.h"
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#include "tree-flow.h"
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#include "tree-inline.h"
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#include "diagnostic.h"
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#include "langhooks.h"
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#include "langhooks-def.h"
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#include "flags.h"
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#include "rtl.h"
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#include "toplev.h"
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#include "tree-dump.h"
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#include "c-pretty-print.h"
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#include "cgraph.h"
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/* The gimplification pass converts the language-dependent trees
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(ld-trees) emitted by the parser into language-independent trees
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(li-trees) that are the target of SSA analysis and transformations.
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Language-independent trees are based on the SIMPLE intermediate
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representation used in the McCAT compiler framework:
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"Designing the McCAT Compiler Based on a Family of Structured
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Intermediate Representations,"
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L. Hendren, C. Donawa, M. Emami, G. Gao, Justiani, and B. Sridharan,
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Proceedings of the 5th International Workshop on Languages and
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Compilers for Parallel Computing, no. 757 in Lecture Notes in
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Computer Science, New Haven, Connecticut, pp. 406-420,
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Springer-Verlag, August 3-5, 1992.
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http://www-acaps.cs.mcgill.ca/info/McCAT/McCAT.html
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Basically, we walk down gimplifying the nodes that we encounter. As we
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walk back up, we check that they fit our constraints, and copy them
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into temporaries if not. */
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/* Local declarations. */
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enum bc_t { bc_break = 0, bc_continue = 1 };
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static struct c_gimplify_ctx
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{
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/* For handling break and continue. */
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tree current_bc_label;
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tree bc_id[2];
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} *ctxp;
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static void
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push_context (void)
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{
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gcc_assert (!ctxp);
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ctxp = (struct c_gimplify_ctx *) xcalloc (1, sizeof (struct c_gimplify_ctx));
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ctxp->bc_id[bc_continue] = get_identifier ("continue");
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ctxp->bc_id[bc_break] = get_identifier ("break");
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}
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static void
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pop_context (void)
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{
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gcc_assert (ctxp && !ctxp->current_bc_label);
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free (ctxp);
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ctxp = NULL;
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}
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/* Gimplification of statement trees. */
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/* Convert the tree representation of FNDECL from C frontend trees to
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GENERIC. */
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void
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c_genericize (tree fndecl)
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{
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FILE *dump_file;
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int local_dump_flags;
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struct cgraph_node *cgn;
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/* Dump the C-specific tree IR. */
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dump_file = dump_begin (TDI_original, &local_dump_flags);
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if (dump_file)
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{
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fprintf (dump_file, "\n;; Function %s",
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lang_hooks.decl_printable_name (fndecl, 2));
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fprintf (dump_file, " (%s)\n",
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IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (fndecl)));
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fprintf (dump_file, ";; enabled by -%s\n", dump_flag_name (TDI_original));
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fprintf (dump_file, "\n");
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if (local_dump_flags & TDF_RAW)
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dump_node (DECL_SAVED_TREE (fndecl),
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TDF_SLIM | local_dump_flags, dump_file);
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else
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print_c_tree (dump_file, DECL_SAVED_TREE (fndecl));
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fprintf (dump_file, "\n");
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dump_end (TDI_original, dump_file);
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}
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/* Go ahead and gimplify for now. */
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push_context ();
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gimplify_function_tree (fndecl);
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pop_context ();
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/* Dump the genericized tree IR. */
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dump_function (TDI_generic, fndecl);
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/* Genericize all nested functions now. We do things in this order so
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that items like VLA sizes are expanded properly in the context of
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the correct function. */
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cgn = cgraph_node (fndecl);
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for (cgn = cgn->nested; cgn ; cgn = cgn->next_nested)
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c_genericize (cgn->decl);
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}
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static void
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add_block_to_enclosing (tree block)
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{
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tree enclosing;
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for (enclosing = gimple_current_bind_expr ();
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enclosing; enclosing = TREE_CHAIN (enclosing))
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if (BIND_EXPR_BLOCK (enclosing))
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break;
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enclosing = BIND_EXPR_BLOCK (enclosing);
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BLOCK_SUBBLOCKS (enclosing) = chainon (BLOCK_SUBBLOCKS (enclosing), block);
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}
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/* Genericize a scope by creating a new BIND_EXPR.
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BLOCK is either a BLOCK representing the scope or a chain of _DECLs.
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In the latter case, we need to create a new BLOCK and add it to the
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BLOCK_SUBBLOCKS of the enclosing block.
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BODY is a chain of C _STMT nodes for the contents of the scope, to be
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genericized. */
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tree
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c_build_bind_expr (tree block, tree body)
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{
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tree decls, bind;
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if (block == NULL_TREE)
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decls = NULL_TREE;
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else if (TREE_CODE (block) == BLOCK)
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decls = BLOCK_VARS (block);
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else
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{
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decls = block;
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if (DECL_ARTIFICIAL (decls))
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block = NULL_TREE;
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else
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{
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block = make_node (BLOCK);
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BLOCK_VARS (block) = decls;
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add_block_to_enclosing (block);
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}
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}
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if (!body)
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body = build_empty_stmt ();
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if (decls || block)
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{
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bind = build3 (BIND_EXPR, void_type_node, decls, body, block);
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TREE_SIDE_EFFECTS (bind) = 1;
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}
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else
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bind = body;
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return bind;
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}
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/* Gimplify an EXPR_STMT node.
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STMT is the statement node.
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PRE_P points to the list where side effects that must happen before
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STMT should be stored.
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POST_P points to the list where side effects that must happen after
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STMT should be stored. */
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static enum gimplify_status
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gimplify_expr_stmt (tree *stmt_p)
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{
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tree stmt = EXPR_STMT_EXPR (*stmt_p);
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if (stmt == error_mark_node)
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stmt = NULL;
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/* Gimplification of a statement expression will nullify the
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statement if all its side effects are moved to *PRE_P and *POST_P.
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In this case we will not want to emit the gimplified statement.
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However, we may still want to emit a warning, so we do that before
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gimplification. */
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if (stmt && (extra_warnings || warn_unused_value))
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{
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if (!TREE_SIDE_EFFECTS (stmt))
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{
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if (!IS_EMPTY_STMT (stmt)
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&& !VOID_TYPE_P (TREE_TYPE (stmt))
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&& !TREE_NO_WARNING (stmt))
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warning ("statement with no effect");
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}
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else if (warn_unused_value)
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warn_if_unused_value (stmt, input_location);
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}
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if (stmt == NULL_TREE)
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stmt = alloc_stmt_list ();
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*stmt_p = stmt;
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return GS_OK;
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}
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/* Begin a scope which can be exited by a break or continue statement. BC
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indicates which.
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Just creates a label and pushes it into the current context. */
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static tree
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begin_bc_block (enum bc_t bc)
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{
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tree label = create_artificial_label ();
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DECL_NAME (label) = ctxp->bc_id[bc];
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TREE_CHAIN (label) = ctxp->current_bc_label;
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ctxp->current_bc_label = label;
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return label;
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}
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/* Finish a scope which can be exited by a break or continue statement.
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LABEL was returned from the most recent call to begin_bc_block. BODY is
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an expression for the contents of the scope.
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If we saw a break (or continue) in the scope, append a LABEL_EXPR to
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body. Otherwise, just forget the label. */
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static tree
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finish_bc_block (tree label, tree body)
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{
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gcc_assert (label == ctxp->current_bc_label);
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if (TREE_USED (label))
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{
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tree t, sl = NULL;
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/* Clear the name so flow can delete the label. */
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DECL_NAME (label) = NULL_TREE;
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t = build1 (LABEL_EXPR, void_type_node, label);
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append_to_statement_list (body, &sl);
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append_to_statement_list (t, &sl);
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body = sl;
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}
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ctxp->current_bc_label = TREE_CHAIN (label);
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TREE_CHAIN (label) = NULL_TREE;
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return body;
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}
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/* Build a GOTO_EXPR to represent a break or continue statement. BC
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indicates which. */
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static tree
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build_bc_goto (enum bc_t bc)
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{
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tree label;
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tree target_name = ctxp->bc_id[bc];
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/* Look for the appropriate type of label. */
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for (label = ctxp->current_bc_label;
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label;
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label = TREE_CHAIN (label))
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if (DECL_NAME (label) == target_name)
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break;
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if (label == NULL_TREE)
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{
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if (bc == bc_break)
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error ("break statement not within loop or switch");
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else
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error ("continue statement not within loop or switch");
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return NULL_TREE;
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}
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/* Mark the label used for finish_bc_block. */
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TREE_USED (label) = 1;
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return build1 (GOTO_EXPR, void_type_node, label);
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}
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/* Build a generic representation of one of the C loop forms. COND is the
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loop condition or NULL_TREE. BODY is the (possibly compound) statement
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controlled by the loop. INCR is the increment expression of a for-loop,
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or NULL_TREE. COND_IS_FIRST indicates whether the condition is
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evaluated before the loop body as in while and for loops, or after the
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loop body as in do-while loops. */
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static tree
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gimplify_c_loop (tree cond, tree body, tree incr, bool cond_is_first)
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{
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tree top, entry, exit, cont_block, break_block, stmt_list, t;
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location_t stmt_locus;
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stmt_locus = input_location;
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stmt_list = NULL_TREE;
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entry = NULL_TREE;
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break_block = begin_bc_block (bc_break);
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cont_block = begin_bc_block (bc_continue);
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/* If condition is zero don't generate a loop construct. */
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if (cond && integer_zerop (cond))
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{
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top = NULL_TREE;
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exit = NULL_TREE;
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if (cond_is_first)
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{
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t = build_bc_goto (bc_break);
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append_to_statement_list (t, &stmt_list);
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}
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}
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else
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{
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/* If we use a LOOP_EXPR here, we have to feed the whole thing
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back through the main gimplifier to lower it. Given that we
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have to gimplify the loop body NOW so that we can resolve
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break/continue stmts, seems easier to just expand to gotos. */
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top = build1 (LABEL_EXPR, void_type_node, NULL_TREE);
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/* If we have an exit condition, then we build an IF with gotos either
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out of the loop, or to the top of it. If there's no exit condition,
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then we just build a jump back to the top. */
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exit = build_and_jump (&LABEL_EXPR_LABEL (top));
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if (cond && !integer_nonzerop (cond))
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{
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t = build_bc_goto (bc_break);
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exit = build3 (COND_EXPR, void_type_node, cond, exit, t);
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exit = fold (exit);
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gimplify_stmt (&exit);
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if (cond_is_first)
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{
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if (incr)
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{
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entry = build1 (LABEL_EXPR, void_type_node, NULL_TREE);
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t = build_and_jump (&LABEL_EXPR_LABEL (entry));
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}
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else
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t = build_bc_goto (bc_continue);
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append_to_statement_list (t, &stmt_list);
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}
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}
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}
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gimplify_stmt (&body);
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gimplify_stmt (&incr);
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body = finish_bc_block (cont_block, body);
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append_to_statement_list (top, &stmt_list);
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append_to_statement_list (body, &stmt_list);
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append_to_statement_list (incr, &stmt_list);
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append_to_statement_list (entry, &stmt_list);
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append_to_statement_list (exit, &stmt_list);
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annotate_all_with_locus (&stmt_list, stmt_locus);
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return finish_bc_block (break_block, stmt_list);
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}
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/* Gimplify a FOR_STMT node. Move the stuff in the for-init-stmt into the
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prequeue and hand off to gimplify_c_loop. */
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static enum gimplify_status
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gimplify_for_stmt (tree *stmt_p, tree *pre_p)
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{
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tree stmt = *stmt_p;
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if (FOR_INIT_STMT (stmt))
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gimplify_and_add (FOR_INIT_STMT (stmt), pre_p);
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*stmt_p = gimplify_c_loop (FOR_COND (stmt), FOR_BODY (stmt),
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FOR_EXPR (stmt), 1);
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return GS_ALL_DONE;
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}
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/* Gimplify a WHILE_STMT node. */
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static enum gimplify_status
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gimplify_while_stmt (tree *stmt_p)
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{
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tree stmt = *stmt_p;
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*stmt_p = gimplify_c_loop (WHILE_COND (stmt), WHILE_BODY (stmt),
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NULL_TREE, 1);
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return GS_ALL_DONE;
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}
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/* Gimplify a DO_STMT node. */
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static enum gimplify_status
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gimplify_do_stmt (tree *stmt_p)
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{
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tree stmt = *stmt_p;
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*stmt_p = gimplify_c_loop (DO_COND (stmt), DO_BODY (stmt),
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NULL_TREE, 0);
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return GS_ALL_DONE;
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}
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/* Genericize a SWITCH_STMT by turning it into a SWITCH_EXPR. */
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static enum gimplify_status
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gimplify_switch_stmt (tree *stmt_p)
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{
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tree stmt = *stmt_p;
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tree break_block, body;
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location_t stmt_locus = input_location;
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break_block = begin_bc_block (bc_break);
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body = SWITCH_BODY (stmt);
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if (!body)
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body = build_empty_stmt ();
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*stmt_p = build3 (SWITCH_EXPR, SWITCH_TYPE (stmt), SWITCH_COND (stmt),
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body, NULL_TREE);
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SET_EXPR_LOCATION (*stmt_p, stmt_locus);
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gimplify_stmt (stmt_p);
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*stmt_p = finish_bc_block (break_block, *stmt_p);
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return GS_ALL_DONE;
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}
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/* Gimplification of expression trees. */
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/* Gimplify a C99 compound literal expression. This just means adding the
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DECL_EXPR before the current EXPR_STMT and using its anonymous decl
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instead. */
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static enum gimplify_status
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gimplify_compound_literal_expr (tree *expr_p, tree *pre_p)
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{
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tree decl_s = COMPOUND_LITERAL_EXPR_DECL_STMT (*expr_p);
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tree decl = DECL_EXPR_DECL (decl_s);
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/* This decl isn't mentioned in the enclosing block, so add it to the
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list of temps. FIXME it seems a bit of a kludge to say that
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anonymous artificial vars aren't pushed, but everything else is. */
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if (DECL_NAME (decl) == NULL_TREE)
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gimple_add_tmp_var (decl);
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gimplify_and_add (decl_s, pre_p);
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*expr_p = decl;
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return GS_OK;
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}
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/* Do C-specific gimplification. Args are as for gimplify_expr. */
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int
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c_gimplify_expr (tree *expr_p, tree *pre_p, tree *post_p ATTRIBUTE_UNUSED)
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{
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enum tree_code code = TREE_CODE (*expr_p);
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switch (code)
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{
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case DECL_EXPR:
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/* This is handled mostly by gimplify.c, but we have to deal with
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not warning about int x = x; as it is a GCC extension to turn off
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this warning but only if warn_init_self is zero. */
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if (TREE_CODE (DECL_EXPR_DECL (*expr_p)) == VAR_DECL
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&& !DECL_EXTERNAL (DECL_EXPR_DECL (*expr_p))
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&& !TREE_STATIC (DECL_EXPR_DECL (*expr_p))
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&& (DECL_INITIAL (DECL_EXPR_DECL (*expr_p))
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== DECL_EXPR_DECL (*expr_p))
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&& !warn_init_self)
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TREE_NO_WARNING (DECL_EXPR_DECL (*expr_p)) = 1;
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return GS_UNHANDLED;
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case COMPOUND_LITERAL_EXPR:
|
|
return gimplify_compound_literal_expr (expr_p, pre_p);
|
|
|
|
case FOR_STMT:
|
|
return gimplify_for_stmt (expr_p, pre_p);
|
|
|
|
case WHILE_STMT:
|
|
return gimplify_while_stmt (expr_p);
|
|
|
|
case DO_STMT:
|
|
return gimplify_do_stmt (expr_p);
|
|
|
|
case SWITCH_STMT:
|
|
return gimplify_switch_stmt (expr_p);
|
|
|
|
case EXPR_STMT:
|
|
return gimplify_expr_stmt (expr_p);
|
|
|
|
case CONTINUE_STMT:
|
|
*expr_p = build_bc_goto (bc_continue);
|
|
return GS_ALL_DONE;
|
|
|
|
case BREAK_STMT:
|
|
*expr_p = build_bc_goto (bc_break);
|
|
return GS_ALL_DONE;
|
|
|
|
default:
|
|
return GS_UNHANDLED;
|
|
}
|
|
}
|