On 4/8/21 5:01 PM, Patrick Palka wrote:
On Thu, 8 Apr 2021, Jason Merrill wrote:
On 4/7/21 12:10 PM, Patrick Palka wrote:
We currently substitute through a lambda's constraints whenever we
regenerate it via tsubst_lambda_expr. This is the wrong approach
because it can lead to hard errors due to constraints being evaluated
out of order (as in the testcase concepts-lambda17.C below), and because
it doesn't mesh well with the recently added REQUIRES_EXPR_EXTRA_ARGS
mechanism for delaying substitution into requires-expressions, which is
the cause of this PR.
But in order to avoid substituting through a lambda's constraints during
regeneration, we we need to be able to get at all in-scope template
parameters and the corresponding template arguments during constraint
checking of a lambda's op(). And this information is not easily
available where we need it, it seems.
To that end, the approach that this patch takes is to add two new fields
to LAMBDA_EXPR (and remove one): LAMBDA_EXPR_REGENERATED_FROM
(replacing LAMBDA_EXPR_INSTANTIATED), and LAMBDA_EXPR_REGENERATING_TARGS.
The former allows us to obtain the complete set of template parameters
that are in-scope for a lambda's op(), and the latter gives us all outer
template arguments that were used to regenerate the lambda.
I'm a little surprised you didn't use a TEMPLATE_INFO for these, but this way
is fine too.
Using a TEMPLATE_INFO here works nicely here, I hadn't considered it.
Like so? Tested on x86_64-pc-linux-gnu.
OK.
-- >8 --
Subject: [PATCH] c++: Use a TEMPLATE_INFO to hold regenerated lambda info
A TEMPLATE_INFO is a natural fit for what LAMBDA_EXPR_REGENERATED_FROM
and LAMBDA_EXPR_REGENERATING_TARGS hold, so let's use it instead.
gcc/cp/ChangeLog:
* cp-tree.h (LAMBDA_EXPR_REGENERATED_FROM)
(LAMBDA_EXPR_REGENERATING_TARGS): Replace these with ...
(LAMBDA_EXPR_REGEN_INFO): ... this.
(tree_lambda_expr::regenerated_from)
(tree_lambda_expr::regenerating_targs): Replace these with ...
(tree_lambda_expr::regen_info): ... this.
* constraint.cc (satisfy_declaration_constraints): Adjust
accordingly.
* lambda.c (build_lambda_expr): Likewise.
* pt.c (regenerated_lambda_fn_p): Likewise.
(most_general_lambda): Likewise.
(tsubst_lambda_expr): Likewise.
---
gcc/cp/constraint.cc | 4 ++--
gcc/cp/cp-tree.h | 18 +++++++-----------
gcc/cp/lambda.c | 3 +--
gcc/cp/pt.c | 15 +++++++++------
4 files changed, 19 insertions(+), 21 deletions(-)
diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 0a9d1bfea0f..0ddb2990dd9 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -3193,7 +3193,7 @@ satisfy_declaration_constraints (tree t, sat_info info)
arguments that were used to regenerate the lambda. */
gcc_assert (!args || TMPL_ARGS_DEPTH (args) == 1);
tree lambda = CLASSTYPE_LAMBDA_EXPR (DECL_CONTEXT (t));
- tree outer_args = LAMBDA_EXPR_REGENERATING_TARGS (lambda);
+ tree outer_args = TI_ARGS (LAMBDA_EXPR_REGEN_INFO (lambda));
if (args)
args = add_to_template_args (outer_args, args);
else
@@ -3256,7 +3256,7 @@ satisfy_declaration_constraints (tree t, tree args,
sat_info info)
/* As in the two-parameter version of this function. */
gcc_assert (TMPL_ARGS_DEPTH (args) == 1);
tree lambda = CLASSTYPE_LAMBDA_EXPR (DECL_CONTEXT (t));
- tree outer_args = LAMBDA_EXPR_REGENERATING_TARGS (lambda);
+ tree outer_args = TI_ARGS (LAMBDA_EXPR_REGEN_INFO (lambda));
args = add_to_template_args (outer_args, args);
}
else
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index bf9d5add0cf..e42b82ae5a4 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -1456,15 +1456,12 @@ enum cp_lambda_default_capture_mode_type {
#define LAMBDA_EXPR_PENDING_PROXIES(NODE) \
(((struct tree_lambda_expr *)LAMBDA_EXPR_CHECK (NODE))->pending_proxies)
-/* The immediate LAMBDA_EXPR from which NODE was regenerated, or NULL_TREE
- (if NODE was not regenerated via tsubst_lambda_expr). */
-#define LAMBDA_EXPR_REGENERATED_FROM(NODE) \
- (((struct tree_lambda_expr *)LAMBDA_EXPR_CHECK (NODE))->regenerated_from)
-
-/* The full set of template arguments used to regenerate NODE, or NULL_TREE
- (if NODE was not regenerated via tsubst_lambda_expr). */
-#define LAMBDA_EXPR_REGENERATING_TARGS(NODE) \
- (((struct tree_lambda_expr *)LAMBDA_EXPR_CHECK (NODE))->regenerating_targs)
+/* If NODE was regenerated via tsubst_lambda_expr, this is a TEMPLATE_INFO
+ whose TI_TEMPLATE is the immediate LAMBDA_EXPR from which NODE was
+ regenerated, and TI_ARGS is the full set of template arguments used
+ to regenerate NODE from the most general lambda. */
+#define LAMBDA_EXPR_REGEN_INFO(NODE) \
+ (((struct tree_lambda_expr *)LAMBDA_EXPR_CHECK (NODE))->regen_info)
/* The closure type of the lambda, which is also the type of the
LAMBDA_EXPR. */
@@ -1477,8 +1474,7 @@ struct GTY (()) tree_lambda_expr
tree capture_list;
tree this_capture;
tree extra_scope;
- tree regenerated_from;
- tree regenerating_targs;
+ tree regen_info;
vec<tree, va_gc> *pending_proxies;
location_t locus;
enum cp_lambda_default_capture_mode_type default_capture_mode : 8;
diff --git a/gcc/cp/lambda.c b/gcc/cp/lambda.c
index c0a5ffb427e..16e2b4c18b4 100644
--- a/gcc/cp/lambda.c
+++ b/gcc/cp/lambda.c
@@ -41,8 +41,7 @@ build_lambda_expr (void)
LAMBDA_EXPR_DEFAULT_CAPTURE_MODE (lambda) = CPLD_NONE;
LAMBDA_EXPR_CAPTURE_LIST (lambda) = NULL_TREE;
LAMBDA_EXPR_THIS_CAPTURE (lambda) = NULL_TREE;
- LAMBDA_EXPR_REGENERATED_FROM (lambda) = NULL_TREE;
- LAMBDA_EXPR_REGENERATING_TARGS (lambda) = NULL_TREE;
+ LAMBDA_EXPR_REGEN_INFO (lambda) = NULL_TREE;
LAMBDA_EXPR_PENDING_PROXIES (lambda) = NULL;
LAMBDA_EXPR_MUTABLE_P (lambda) = false;
return lambda;
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index daf1b5aeb32..01c807be1bb 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -14356,7 +14356,7 @@ regenerated_lambda_fn_p (tree fn)
return false;
tree closure = DECL_CONTEXT (fn);
tree lam = CLASSTYPE_LAMBDA_EXPR (closure);
- return LAMBDA_EXPR_REGENERATED_FROM (lam) != NULL_TREE;
+ return LAMBDA_EXPR_REGEN_INFO (lam) != NULL_TREE;
}
/* Return the LAMBDA_EXPR from which T was ultimately regenerated.
@@ -14365,8 +14365,8 @@ regenerated_lambda_fn_p (tree fn)
tree
most_general_lambda (tree t)
{
- while (LAMBDA_EXPR_REGENERATED_FROM (t))
- t = LAMBDA_EXPR_REGENERATED_FROM (t);
+ while (tree ti = LAMBDA_EXPR_REGEN_INFO (t))
+ t = TI_TEMPLATE (ti);
return t;
}
@@ -19278,9 +19278,12 @@ tsubst_lambda_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl)
LAMBDA_EXPR_DEFAULT_CAPTURE_MODE (r)
= LAMBDA_EXPR_DEFAULT_CAPTURE_MODE (t);
LAMBDA_EXPR_MUTABLE_P (r) = LAMBDA_EXPR_MUTABLE_P (t);
- LAMBDA_EXPR_REGENERATED_FROM (r) = t;
- LAMBDA_EXPR_REGENERATING_TARGS (r)
- = add_to_template_args (LAMBDA_EXPR_REGENERATING_TARGS (t), args);
+ if (tree ti = LAMBDA_EXPR_REGEN_INFO (t))
+ LAMBDA_EXPR_REGEN_INFO (r)
+ = build_template_info (t, add_to_template_args (TI_ARGS (ti), args));
+ else
+ LAMBDA_EXPR_REGEN_INFO (r)
+ = build_template_info (t, args);
gcc_assert (LAMBDA_EXPR_THIS_CAPTURE (t) == NULL_TREE
&& LAMBDA_EXPR_PENDING_PROXIES (t) == NULL);
