Iain,
this is the first of 2 patches I needed on top of your github WIP
series. It is against GCC-10, but AFAICT will also be needed on trunk.
We were not descending into the object operand of COMPONENT_REF exprs,
and end up bitcopying a field out of a temporary, leading to badness.
The breaking out of replace_unary_preamble is merely coincidental
simplification.
I also think one needs to descend the second operand of COMPOUND_EXPR,
but when I did that badness happens, probably because of the artificial
COMPOUND_EXPRs that get generated, which you mentioned?
The bug manifested itself in Folly, and it was too difficult to extract
a testcase.
nathan
--
Nathan Sidwell
Summary:
The ported coroutine patches still contained a bug. It could
cause object slicing and bit copying when the compiler got confused
about the lifetime of a member access. It needs to look at the object
being accessed, not just the data member.
diff --git a/9.x/src/gcc-10.x/gcc/cp/coroutines.cc b/9.x/src/gcc-10.x/gcc/cp/coroutines.cc
index d0f292f2a6..ee004d5b98 100644
--- a/9.x/src/gcc-10.x/gcc/cp/coroutines.cc
+++ b/9.x/src/gcc-10.x/gcc/cp/coroutines.cc
@@ -3007,6 +3007,7 @@ struct coro_flattened_statement {
static tree *find_unary_preamble (tree, bool&);
static bool expr_result_needs_frame_temp (tree);
+ static tree replace_unary_preamble (tree unary, tree replace);
tree get_flattened_statement (tree);
void build_flattened_statement ();
@@ -3565,15 +3566,15 @@ tree *
coro_flattened_statement::find_unary_preamble (tree expr, bool& addr_taken)
{
tree *non_u_ptr = NULL;
- bool done = false;
/* Find the first non-unary operation in an expression. */
- while (!done)
+ for (;;)
if (UNARY_CLASS_P (expr)
- || (EXPRESSION_CLASS_P (expr)
- && TREE_CODE_LENGTH (TREE_CODE (expr)) == 1)
|| TREE_CODE (expr) == INDIRECT_REF
- || TREE_CODE (expr) == VIEW_CONVERT_EXPR)
+ || TREE_CODE (expr) == VIEW_CONVERT_EXPR
+ || TREE_CODE (expr) == COMPONENT_REF
+ || (EXPRESSION_CLASS_P (expr)
+ && TREE_CODE_LENGTH (TREE_CODE (expr)) == 1))
{
if (TREE_CODE (expr) == STMT_EXPR
|| TREE_CODE (expr) == CLEANUP_POINT_EXPR)
@@ -3582,14 +3583,24 @@ coro_flattened_statement::find_unary_preamble (tree expr, bool& addr_taken)
if (TREE_CODE (expr) == ADDR_EXPR)
addr_taken = true;
non_u_ptr = &TREE_OPERAND (expr, 0);
- expr = TREE_OPERAND (expr, 0);
+ expr = *non_u_ptr;
}
else
- done = true;
+ break;
return non_u_ptr;
}
+tree coro_flattened_statement::replace_unary_preamble (tree unary, tree replace)
+{
+ tree *slot = &unary;
+ while (*slot)
+ slot = &TREE_OPERAND (*slot, 0);
+ *slot = replace;
+
+ return unary;
+}
+
/* EXPR is an expression with a result that must persist across one or more
suspension points, does this need a frame var? */
@@ -3639,15 +3650,7 @@ coro_flattened_statement::flatten_aggr_init (var_nest_node *t, tree expr,
handle_call_param (t, &AGGR_INIT_EXPR_ARG (expr, p_num), "AI");
/* [A = ] <unary ops> revised_call. */
- if (unary_preamble)
- {
- gcc_checking_assert (!VOID_TYPE_P (TREE_TYPE (expr)));
- tree x_op = unary_preamble;
- while (TREE_OPERAND (x_op, 0))
- x_op = TREE_OPERAND (x_op, 0);
- TREE_OPERAND (x_op, 0) = expr;
- expr = unary_preamble;
- }
+ expr = replace_unary_preamble (unary_preamble, expr);
if (!discarded)
expr = build2_loc (loc, expr_code, TREE_TYPE (t->var), t->var, expr);
@@ -3710,14 +3713,7 @@ coro_flattened_statement::flatten_await (var_nest_node *t, tree expr,
flatten_await_inner (t, expr);
/* [A = ] <unary ops> expr. */
- if (unary_preamble)
- {
- tree x_op = unary_preamble;
- while (TREE_OPERAND (x_op, 0))
- x_op = TREE_OPERAND (x_op, 0);
- TREE_OPERAND (x_op, 0) = expr;
- expr = unary_preamble;
- }
+ expr = replace_unary_preamble (unary_preamble, expr);
if (!discarded)
expr = build2_loc (loc, expr_code, TREE_TYPE (t->var), t->var, expr);
@@ -3790,14 +3786,7 @@ coro_flattened_statement::flatten_binary (var_nest_node *t, tree expr,
flatten_expression (ins); /* Recurse into the second sub-expr... */
}
- if (unary_preamble)
- {
- tree x_op = unary_preamble;
- while (TREE_OPERAND (x_op, 0))
- x_op = TREE_OPERAND (x_op, 0);
- TREE_OPERAND (x_op, 0) = expr;
- expr = unary_preamble;
- }
+ expr = replace_unary_preamble (unary_preamble, expr);
if (!discarded)
expr = build2_loc (loc, expr_code, TREE_TYPE (t->var), t->var, expr);
@@ -3890,14 +3879,7 @@ coro_flattened_statement::flatten_call (var_nest_node *t, tree expr,
handle_call_param (t, &CALL_EXPR_ARG(expr, p_num), "CT");
/* [A = ] <unary ops> revised_call. */
- if (unary_preamble)
- {
- tree x_op = unary_preamble;
- while (TREE_OPERAND (x_op, 0))
- x_op = TREE_OPERAND (x_op, 0);
- TREE_OPERAND (x_op, 0) = expr;
- expr = unary_preamble;
- }
+ expr = replace_unary_preamble (unary_preamble, expr);
if (!discarded)
expr = build2_loc (loc, expr_code, TREE_TYPE (t->var), t->var, expr);
@@ -3933,16 +3915,7 @@ coro_flattened_statement::flatten_cleanup (var_nest_node *t, tree expr,
flatten_expression (t->then_cl); /* Recurse into the sub-expr... */
/* [A = ] <unary ops> tmp. */
- if (unary_preamble)
- {
- tree x_op = unary_preamble;
- while (TREE_OPERAND (x_op, 0))
- x_op = TREE_OPERAND (x_op, 0);
- TREE_OPERAND (x_op, 0) = tmp;
- expr = unary_preamble;
- }
- else
- expr = tmp;
+ expr = replace_unary_preamble (unary_preamble, tmp);
if (!discarded)
expr = build2_loc (loc, expr_code, TREE_TYPE (t->var), t->var, tmp);
t->init = expr;
@@ -3988,14 +3961,7 @@ coro_flattened_statement::flatten_compound (var_nest_node *t, tree expr,
/* The second operand of the compound becomes the new expression. */
tree second = TREE_OPERAND (expr, 1);
- if (unary_preamble)
- {
- tree x_op = unary_preamble;
- while (TREE_OPERAND (x_op, 0))
- x_op = TREE_OPERAND (x_op, 0);
- TREE_OPERAND (x_op, 0) = second;
- second = unary_preamble;
- }
+ second = replace_unary_preamble (unary_preamble, second);
if (!discarded)
second = build2_loc (loc, expr_code, TREE_TYPE (t->var), t->var, second);
@@ -4031,14 +3997,7 @@ coro_flattened_statement::flatten_constructor (var_nest_node *t, tree expr,
}
/* Reassemble the original. */
- if (unary_preamble)
- {
- tree x_op = unary_preamble;
- while (TREE_OPERAND (x_op, 0))
- x_op = TREE_OPERAND (x_op, 0);
- TREE_OPERAND (x_op, 0) = expr;
- expr = unary_preamble;
- }
+ expr = replace_unary_preamble (unary_preamble, expr);
if (!discarded)
expr = build2_loc (loc, expr_code, TREE_TYPE (t->var), t->var, expr);
@@ -4107,10 +4066,8 @@ coro_flattened_statement::flatten_target (var_nest_node *t, tree expr,
/* There must be an await expression in here, so recurse with a 'bare'
target expr. */
flatten_expression (ins);
- tree x_op = unary_preamble;
- while (TREE_OPERAND (x_op, 0))
- x_op = TREE_OPERAND (x_op, 0);
- TREE_OPERAND (x_op, 0) = var;
+ gcc_assert (unary_preamble);
+ replace_unary_preamble (unary_preamble, var);
expr = unary_preamble;
if (!discarded)
expr = build2_loc (loc, expr_code, TREE_TYPE (t->var), t->var, expr);
@@ -4225,21 +4182,10 @@ coro_flattened_statement::flatten_ternary (var_nest_node *t, tree expr,
? copy_node (unary_preamble)
: unary_preamble;
if (apply_uops_then)
- {
- tree x_op = t_op;
- while (TREE_OPERAND (x_op, 0))
- x_op = TREE_OPERAND (x_op, 0);
- TREE_OPERAND (x_op, 0) = then_;
- then_ = t_op;
- }
+ then_ = replace_unary_preamble (t_op, then_);
+
if (apply_uops_else)
- {
- tree x_op = unary_preamble;
- while (TREE_OPERAND (x_op, 0))
- x_op = TREE_OPERAND (x_op, 0);
- TREE_OPERAND (x_op, 0) = else_;
- else_ = unary_preamble;
- }
+ else_ = replace_unary_preamble (unary_preamble, else_);
}
if (!discarded && apply_uops_then)
@@ -4270,14 +4216,7 @@ coro_flattened_statement::flatten_ternary (var_nest_node *t, tree expr,
{
/* The only replacement is the condition, so that we preserve the ternary
and any unary preamble. */
- if (unary_preamble)
- {
- tree x_op = unary_preamble;
- while (TREE_OPERAND (x_op, 0))
- x_op = TREE_OPERAND (x_op, 0);
- TREE_OPERAND (x_op, 0) = expr;
- expr = unary_preamble;
- }
+ expr = replace_unary_preamble (unary_preamble, expr);
if (!discarded)
expr = build2_loc (loc, expr_code, res_type, t->var, expr);
}
@@ -4361,10 +4300,7 @@ coro_flattened_statement::flatten_truth_if (var_nest_node *t, tree expr,
ins->then_cl = then_cl;
ins->synthesized_var_p = synthetic;
/* <unary ops> x. */
- tree x_op = unary_preamble;
- while (TREE_OPERAND (x_op, 0))
- x_op = TREE_OPERAND (x_op, 0);
- TREE_OPERAND (x_op, 0) = var;
+ replace_unary_preamble (unary_preamble, var);
if (!discarded)
init = build2_loc (loc, expr_code, expr_type, t->var, unary_preamble);
else
@@ -4454,11 +4390,7 @@ coro_flattened_statement::flatten_expression (var_nest_node *t)
else if (unary_preamble)
{
/* Undo the split. */
- tree x_op = unary_preamble;
- while (TREE_OPERAND (x_op, 0))
- x_op = TREE_OPERAND (x_op, 0);
- TREE_OPERAND (x_op, 0) = expr;
- expr = unary_preamble;
+ expr = replace_unary_preamble (unary_preamble, expr);
}
if (!discarded)
expr = build2_loc (loc, expr_code, TREE_TYPE (t->var), t->var, expr);
--
2.30.2
