/* Dead code elimination pass for the GNU compiler.
- Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
+ Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011
Free Software Foundation, Inc.
Contributed by Ben Elliston <bje@redhat.com>
and Andrew MacLeod <amacleod@redhat.com>
static void
mark_stmt_if_obviously_necessary (gimple stmt, bool aggressive)
{
- tree lhs = NULL_TREE;
-
/* With non-call exceptions, we have to assume that all statements could
throw. If a statement may throw, it is inherently necessary. */
if (cfun->can_throw_non_call_exceptions && stmt_could_throw_p (stmt))
return;
case GIMPLE_CALL:
- /* Most, but not all function calls are required. Function calls that
- produce no result and have no side effects (i.e. const pure
- functions) are unnecessary. */
- if (gimple_has_side_effects (stmt))
- {
- mark_stmt_necessary (stmt, true);
+ {
+ tree callee = gimple_call_fndecl (stmt);
+ if (callee != NULL_TREE
+ && DECL_BUILT_IN_CLASS (callee) == BUILT_IN_NORMAL)
+ switch (DECL_FUNCTION_CODE (callee))
+ {
+ case BUILT_IN_MALLOC:
+ case BUILT_IN_CALLOC:
+ case BUILT_IN_ALLOCA:
+ return;
+
+ default:;
+ }
+ /* Most, but not all function calls are required. Function calls that
+ produce no result and have no side effects (i.e. const pure
+ functions) are unnecessary. */
+ if (gimple_has_side_effects (stmt))
+ {
+ mark_stmt_necessary (stmt, true);
+ return;
+ }
+ if (!gimple_call_lhs (stmt))
return;
- }
- if (!gimple_call_lhs (stmt))
- return;
- lhs = gimple_call_lhs (stmt);
- /* Fall through */
-
- case GIMPLE_ASSIGN:
- if (!lhs)
- lhs = gimple_assign_lhs (stmt);
- break;
+ break;
+ }
case GIMPLE_DEBUG:
/* Debug temps without a value are not useful. ??? If we could
easily locate the debug temp bind stmt for a use thereof,
would could refrain from marking all debug temps here, and
mark them only if they're used. */
- if (gimple_debug_bind_has_value_p (stmt)
+ if (!gimple_debug_bind_p (stmt)
+ || gimple_debug_bind_has_value_p (stmt)
|| TREE_CODE (gimple_debug_bind_get_var (stmt)) != DEBUG_EXPR_DECL)
mark_stmt_necessary (stmt, false);
return;
static bool
ref_may_be_aliased (tree ref)
{
+ gcc_assert (TREE_CODE (ref) != WITH_SIZE_EXPR);
while (handled_component_p (ref))
ref = TREE_OPERAND (ref, 0);
if (TREE_CODE (ref) == MEM_REF
/* If the stmt lhs kills ref, then we can stop walking. */
if (gimple_has_lhs (def_stmt)
- && TREE_CODE (gimple_get_lhs (def_stmt)) != SSA_NAME)
+ && TREE_CODE (gimple_get_lhs (def_stmt)) != SSA_NAME
+ /* The assignment is not necessarily carried out if it can throw
+ and we can catch it in the current function where we could inspect
+ the previous value.
+ ??? We only need to care about the RHS throwing. For aggregate
+ assignments or similar calls and non-call exceptions the LHS
+ might throw as well. */
+ && !stmt_can_throw_internal (def_stmt))
{
tree base, lhs = gimple_get_lhs (def_stmt);
HOST_WIDE_INT size, offset, max_size;
return false;
}
+ /* We want to skip statments that do not constitute stores but have
+ a virtual definition. */
+ if (is_gimple_call (def_stmt))
+ {
+ tree callee = gimple_call_fndecl (def_stmt);
+ if (callee != NULL_TREE
+ && DECL_BUILT_IN_CLASS (callee) == BUILT_IN_NORMAL)
+ switch (DECL_FUNCTION_CODE (callee))
+ {
+ case BUILT_IN_MALLOC:
+ case BUILT_IN_CALLOC:
+ case BUILT_IN_ALLOCA:
+ case BUILT_IN_FREE:
+ return false;
+
+ default:;
+ }
+ }
+
mark_operand_necessary (vdef);
return false;
ssa_op_iter iter;
tree use;
+ /* If this is a call to free which is directly fed by an
+ allocation function do not mark that necessary through
+ processing the argument. */
+ if (gimple_call_builtin_p (stmt, BUILT_IN_FREE))
+ {
+ tree ptr = gimple_call_arg (stmt, 0);
+ gimple def_stmt;
+ tree def_callee;
+ /* If the pointer we free is defined by an allocation
+ function do not add the call to the worklist. */
+ if (TREE_CODE (ptr) == SSA_NAME
+ && is_gimple_call (def_stmt = SSA_NAME_DEF_STMT (ptr))
+ && (def_callee = gimple_call_fndecl (def_stmt))
+ && DECL_BUILT_IN_CLASS (def_callee) == BUILT_IN_NORMAL
+ && (DECL_FUNCTION_CODE (def_callee) == BUILT_IN_MALLOC
+ || DECL_FUNCTION_CODE (def_callee) == BUILT_IN_CALLOC))
+ continue;
+ }
+
FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE)
mark_operand_necessary (use);
if (callee != NULL_TREE
&& DECL_BUILT_IN_CLASS (callee) == BUILT_IN_NORMAL
&& (DECL_FUNCTION_CODE (callee) == BUILT_IN_MEMSET
+ || DECL_FUNCTION_CODE (callee) == BUILT_IN_MEMSET_CHK
|| DECL_FUNCTION_CODE (callee) == BUILT_IN_MALLOC
- || DECL_FUNCTION_CODE (callee) == BUILT_IN_FREE))
+ || DECL_FUNCTION_CODE (callee) == BUILT_IN_CALLOC
+ || DECL_FUNCTION_CODE (callee) == BUILT_IN_FREE
+ || DECL_FUNCTION_CODE (callee) == BUILT_IN_VA_END
+ || DECL_FUNCTION_CODE (callee) == BUILT_IN_ALLOCA
+ || DECL_FUNCTION_CODE (callee) == BUILT_IN_STACK_SAVE
+ || DECL_FUNCTION_CODE (callee) == BUILT_IN_STACK_RESTORE
+ || DECL_FUNCTION_CODE (callee) == BUILT_IN_ASSUME_ALIGNED))
continue;
/* Calls implicitly load from memory, their arguments
if (TREE_CODE (arg) == SSA_NAME
|| is_gimple_min_invariant (arg))
continue;
+ if (TREE_CODE (arg) == WITH_SIZE_EXPR)
+ arg = TREE_OPERAND (arg, 0);
if (!ref_may_be_aliased (arg))
mark_aliased_reaching_defs_necessary (stmt, arg);
}
{
tree rhs = gimple_return_retval (stmt);
/* A return statement may perform a load. */
- if (TREE_CODE (rhs) != SSA_NAME
+ if (rhs
+ && TREE_CODE (rhs) != SSA_NAME
&& !is_gimple_min_invariant (rhs))
{
if (!ref_may_be_aliased (rhs))
stats.total++;
+ /* We can mark a call to free as not necessary if the
+ defining statement of its argument is an allocation
+ function and that is not necessary itself. */
+ if (gimple_call_builtin_p (stmt, BUILT_IN_FREE))
+ {
+ tree ptr = gimple_call_arg (stmt, 0);
+ tree callee2;
+ gimple def_stmt;
+ if (TREE_CODE (ptr) != SSA_NAME)
+ continue;
+ def_stmt = SSA_NAME_DEF_STMT (ptr);
+ if (!is_gimple_call (def_stmt)
+ || gimple_plf (def_stmt, STMT_NECESSARY))
+ continue;
+ callee2 = gimple_call_fndecl (def_stmt);
+ if (callee2 == NULL_TREE
+ || DECL_BUILT_IN_CLASS (callee2) != BUILT_IN_NORMAL
+ || (DECL_FUNCTION_CODE (callee2) != BUILT_IN_MALLOC
+ && DECL_FUNCTION_CODE (callee2) != BUILT_IN_CALLOC))
+ continue;
+ gimple_set_plf (stmt, STMT_NECESSARY, false);
+ }
+
/* If GSI is not necessary then remove it. */
if (!gimple_plf (stmt, STMT_NECESSARY))
{
struct edge_list *el = NULL;
bool something_changed = 0;
+ calculate_dominance_info (CDI_DOMINATORS);
+
/* Preheaders are needed for SCEV to work.
Simple lateches and recorded exits improve chances that loop will
proved to be finite in testcases such as in loop-15.c and loop-24.c */
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
- TODO_dump_func | TODO_verify_ssa /* todo_flags_finish */
+ TODO_verify_ssa /* todo_flags_finish */
}
};
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
- TODO_dump_func | TODO_verify_ssa /* todo_flags_finish */
+ TODO_verify_ssa /* todo_flags_finish */
}
};
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
- TODO_dump_func | TODO_verify_ssa
+ TODO_verify_ssa
| TODO_verify_flow /* todo_flags_finish */
}
};
OSDN Git Service
