390 lines
12 KiB
C
390 lines
12 KiB
C
/* This plugin contains an analysis pass that detects and warns about
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self-assignment statements. */
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/* { dg-options "-O" } */
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#include "gcc-plugin.h"
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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 "stringpool.h"
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#include "toplev.h"
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#include "basic-block.h"
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#include "hash-table.h"
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#include "vec.h"
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#include "ggc.h"
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#include "basic-block.h"
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#include "tree-ssa-alias.h"
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#include "internal-fn.h"
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#include "gimple-fold.h"
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#include "tree-eh.h"
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#include "gimple-expr.h"
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#include "is-a.h"
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#include "gimple.h"
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#include "gimple-iterator.h"
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#include "tree.h"
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#include "tree-pass.h"
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#include "intl.h"
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#include "plugin-version.h"
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#include "diagnostic.h"
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#include "context.h"
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int plugin_is_GPL_compatible;
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/* Indicate whether to check overloaded operator '=', which is performed by
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default. To disable it, use -fplugin-arg-NAME-no-check-operator-eq. */
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bool check_operator_eq = true;
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/* Given a rhs EXPR of a gimple assign statement, if it is
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- SSA_NAME : returns its var decl, or, if it is a temp variable,
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returns the rhs of its SSA def statement.
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- VAR_DECL, PARM_DECL, FIELD_DECL, or a reference expression :
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returns EXPR itself.
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- any other expression : returns NULL_TREE. */
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static tree
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get_real_ref_rhs (tree expr)
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{
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switch (TREE_CODE (expr))
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{
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case SSA_NAME:
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{
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/* Given a self-assign statement, say foo.x = foo.x,
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the IR (after SSA) looks like:
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D.1797_14 = foo.x;
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foo.x ={v} D.1797_14;
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So if the rhs EXPR is an SSA_NAME of a temp variable,
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e.g. D.1797_14, we need to grab the rhs of its SSA def
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statement (i.e. foo.x). */
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tree vdecl = SSA_NAME_VAR (expr);
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if ((!vdecl || DECL_ARTIFICIAL (vdecl))
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&& !gimple_nop_p (SSA_NAME_DEF_STMT (expr)))
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{
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gimple *def_stmt = SSA_NAME_DEF_STMT (expr);
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/* We are only interested in an assignment with a single
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rhs operand because if it is not, the original assignment
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will not possibly be a self-assignment. */
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if (gimple_assign_single_p (def_stmt))
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return get_real_ref_rhs (gimple_assign_rhs1 (def_stmt));
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else
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return NULL_TREE;
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}
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else
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return vdecl;
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}
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case VAR_DECL:
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case PARM_DECL:
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case FIELD_DECL:
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case COMPONENT_REF:
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case MEM_REF:
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case ARRAY_REF:
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return expr;
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default:
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return NULL_TREE;
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}
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}
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/* Given an expression tree, EXPR, that may contains SSA names, returns an
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equivalent tree with the SSA names converted to var/parm/field decls
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so that it can be used with '%E' format modifier when emitting warning
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messages.
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This function currently only supports VAR/PARM/FIELD_DECL, reference
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expressions (COMPONENT_REF, INDIRECT_REF, ARRAY_REF), integer constant,
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and SSA_NAME. If EXPR contains any other tree nodes (e.g. an arithmetic
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expression appears in array index), NULL_TREE is returned. */
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static tree
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get_non_ssa_expr (tree expr)
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{
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if (!expr)
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return NULL_TREE;
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switch (TREE_CODE (expr))
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{
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case VAR_DECL:
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case PARM_DECL:
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case FIELD_DECL:
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{
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if (DECL_NAME (expr))
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return expr;
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else
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return NULL_TREE;
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}
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case COMPONENT_REF:
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{
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tree base, orig_base = TREE_OPERAND (expr, 0);
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tree component, orig_component = TREE_OPERAND (expr, 1);
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base = get_non_ssa_expr (orig_base);
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if (!base)
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return NULL_TREE;
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component = get_non_ssa_expr (orig_component);
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if (!component)
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return NULL_TREE;
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/* If either BASE or COMPONENT is converted, build a new
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component reference tree. */
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if (base != orig_base || component != orig_component)
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return build3 (COMPONENT_REF, TREE_TYPE (component),
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base, component, NULL_TREE);
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else
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return expr;
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}
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case MEM_REF:
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{
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tree orig_base = TREE_OPERAND (expr, 0);
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if (TREE_CODE (orig_base) == SSA_NAME)
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{
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tree base = get_non_ssa_expr (orig_base);
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if (!base)
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return NULL_TREE;
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return fold_build2 (MEM_REF, TREE_TYPE (expr),
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base, TREE_OPERAND (expr, 1));
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}
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return expr;
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}
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case ARRAY_REF:
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{
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tree array, orig_array = TREE_OPERAND (expr, 0);
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tree index, orig_index = TREE_OPERAND (expr, 1);
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array = get_non_ssa_expr (orig_array);
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if (!array)
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return NULL_TREE;
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index = get_non_ssa_expr (orig_index);
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if (!index)
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return NULL_TREE;
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/* If either ARRAY or INDEX is converted, build a new array
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reference tree. */
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if (array != orig_array || index != orig_index)
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return build4 (ARRAY_REF, TREE_TYPE (expr), array, index,
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TREE_OPERAND (expr, 2), TREE_OPERAND (expr, 3));
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else
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return expr;
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}
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case SSA_NAME:
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{
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tree vdecl = SSA_NAME_VAR (expr);
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if ((!vdecl || DECL_ARTIFICIAL (vdecl))
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&& !gimple_nop_p (SSA_NAME_DEF_STMT (expr)))
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{
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gimple *def_stmt = SSA_NAME_DEF_STMT (expr);
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if (gimple_assign_single_p (def_stmt))
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vdecl = gimple_assign_rhs1 (def_stmt);
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}
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return get_non_ssa_expr (vdecl);
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}
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case INTEGER_CST:
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return expr;
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default:
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/* Return NULL_TREE for any other kind of tree nodes. */
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return NULL_TREE;
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}
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}
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/* Given the LHS and (real) RHS of a gimple assign statement, STMT, check if
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they are the same. If so, print a warning message about self-assignment. */
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static void
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compare_and_warn (gimple *stmt, tree lhs, tree rhs)
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{
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if (operand_equal_p (lhs, rhs, OEP_PURE_SAME))
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{
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location_t location;
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location = (gimple_has_location (stmt)
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? gimple_location (stmt)
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: (DECL_P (lhs)
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? DECL_SOURCE_LOCATION (lhs)
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: input_location));
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/* If LHS contains any tree node not currently supported by
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get_non_ssa_expr, simply emit a generic warning without
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specifying LHS in the message. */
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lhs = get_non_ssa_expr (lhs);
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if (lhs)
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warning_at (location, 0, G_("%qE is assigned to itself"), lhs);
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else
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warning_at (location, 0, G_("self-assignment detected"));
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}
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}
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/* Check and warn if STMT is a self-assign statement. */
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static void
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warn_self_assign (gimple *stmt)
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{
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tree rhs, lhs;
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/* Check assigment statement. */
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if (gimple_assign_single_p (stmt))
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{
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rhs = get_real_ref_rhs (gimple_assign_rhs1 (stmt));
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if (!rhs)
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return;
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lhs = gimple_assign_lhs (stmt);
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if (TREE_CODE (lhs) == SSA_NAME)
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{
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lhs = SSA_NAME_VAR (lhs);
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if (!lhs || DECL_ARTIFICIAL (lhs))
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return;
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}
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compare_and_warn (stmt, lhs, rhs);
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}
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/* Check overloaded operator '=' (if enabled). */
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else if (check_operator_eq && is_gimple_call (stmt))
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{
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tree fdecl = gimple_call_fndecl (stmt);
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if (fdecl && (DECL_NAME (fdecl) == maybe_get_identifier ("operator=")))
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{
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/* If 'operator=' takes reference operands, the arguments will be
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ADDR_EXPR trees. In this case, just remove the address-taken
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operator before we compare the lhs and rhs. */
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lhs = gimple_call_arg (stmt, 0);
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if (TREE_CODE (lhs) == ADDR_EXPR)
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lhs = TREE_OPERAND (lhs, 0);
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rhs = gimple_call_arg (stmt, 1);
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if (TREE_CODE (rhs) == ADDR_EXPR)
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rhs = TREE_OPERAND (rhs, 0);
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compare_and_warn (stmt, lhs, rhs);
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}
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}
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}
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namespace {
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const pass_data pass_data_warn_self_assign =
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{
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GIMPLE_PASS, /* type */
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"warn_self_assign", /* name */
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OPTGROUP_NONE, /* optinfo_flags */
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TV_NONE, /* tv_id */
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PROP_ssa, /* properties_required */
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0, /* properties_provided */
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0, /* properties_destroyed */
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0, /* todo_flags_start */
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0, /* todo_flags_finish */
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};
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class pass_warn_self_assign : public gimple_opt_pass
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{
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public:
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pass_warn_self_assign(gcc::context *ctxt)
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: gimple_opt_pass(pass_data_warn_self_assign, ctxt)
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{}
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/* opt_pass methods: */
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bool gate (function *) { return true; }
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virtual unsigned int execute (function *);
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}; // class pass_warn_self_assign
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unsigned int
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pass_warn_self_assign::execute (function *fun)
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{
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gimple_stmt_iterator gsi;
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basic_block bb;
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FOR_EACH_BB_FN (bb, fun)
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{
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for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
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warn_self_assign (gsi_stmt (gsi));
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}
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return 0;
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}
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} // anon namespace
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static gimple_opt_pass *
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make_pass_warn_self_assign (gcc::context *ctxt)
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{
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return new pass_warn_self_assign (ctxt);
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}
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/* The initialization routine exposed to and called by GCC. The spec of this
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function is defined in gcc/gcc-plugin.h.
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PLUGIN_NAME - name of the plugin (useful for error reporting)
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ARGC - the size of the ARGV array
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ARGV - an array of key-value argument pair
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Returns 0 if initialization finishes successfully.
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Note that this function needs to be named exactly "plugin_init". */
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int
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plugin_init (struct plugin_name_args *plugin_info,
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struct plugin_gcc_version *version)
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{
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struct register_pass_info pass_info;
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const char *plugin_name = plugin_info->base_name;
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int argc = plugin_info->argc;
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struct plugin_argument *argv = plugin_info->argv;
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bool enabled = true;
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int i;
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if (!plugin_default_version_check (version, &gcc_version))
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return 1;
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/* Self-assign detection should happen after SSA is constructed. */
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pass_info.pass = make_pass_warn_self_assign (g);
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pass_info.reference_pass_name = "ssa";
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pass_info.ref_pass_instance_number = 1;
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pass_info.pos_op = PASS_POS_INSERT_AFTER;
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/* Process the plugin arguments. This plugin takes the following arguments:
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check-operator-eq, no-check-operator-eq, enable, and disable.
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By default, the analysis is enabled with 'operator=' checked. */
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for (i = 0; i < argc; ++i)
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{
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if (!strcmp (argv[i].key, "check-operator-eq"))
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{
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if (argv[i].value)
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warning (0, G_("option '-fplugin-arg-%s-check-operator-eq=%s'"
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" ignored (superfluous '=%s')"),
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plugin_name, argv[i].value, argv[i].value);
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else
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check_operator_eq = true;
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}
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else if (!strcmp (argv[i].key, "no-check-operator-eq"))
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{
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if (argv[i].value)
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warning (0, G_("option '-fplugin-arg-%s-no-check-operator-eq=%s'"
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" ignored (superfluous '=%s')"),
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plugin_name, argv[i].value, argv[i].value);
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else
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check_operator_eq = false;
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}
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else if (!strcmp (argv[i].key, "enable"))
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{
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if (argv[i].value)
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warning (0, G_("option '-fplugin-arg-%s-enable=%s' ignored"
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" (superfluous '=%s')"),
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plugin_name, argv[i].value, argv[i].value);
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else
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enabled = true;
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}
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else if (!strcmp (argv[i].key, "disable"))
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{
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if (argv[i].value)
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warning (0, G_("option '-fplugin-arg-%s-disable=%s' ignored"
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" (superfluous '=%s')"),
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plugin_name, argv[i].value, argv[i].value);
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else
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enabled = false;
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}
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else
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warning (0, G_("plugin %qs: unrecognized argument %qs ignored"),
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plugin_name, argv[i].key);
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}
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/* Register this new pass with GCC if the analysis is enabled. */
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if (enabled)
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register_callback (plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL,
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&pass_info);
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return 0;
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}
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