c++: per-scope, per-signature lambda discriminators

This implements ABI-compliant lambda discriminators.  Not only do we
have per-scope counters, but we also distinguish by lambda signature.
Only lambdas with the same signature will need non-zero
discriminators.  As the discriminator is signature-dependent, we have
to process the lambda function's declaration before we can determine
it.  For templated and generic lambdas the signature is that of the
uninstantiated lambda -- not separate for each instantiation.

With this change, gcc and clang now produce the same lambda manglings
for all these testcases.

	gcc/cp/
	* cp-tree.h (LAMBDA_EXPR_SCOPE_SIG_DISCRIMINATOR): New.
	(struct tree_lambda_expr): Add discriminator_sig bitfield.
	(recrd_lambda_scope_sig_discriminator): Declare.
	* lambda.cc (struct lambda_sig_count): New.
	(lambda_discriminator): Add signature vector.
	(start_lambda_scope): Adjust.
	(compare_lambda_template_head, compare_lambda_sig): New.
	(record_lambda_scope_sig_discriminator): New.
	* mangle.cc (write_closure_type): Use the scope-sig discriminator for
	ABI >= 18.  Emit abi mangling warning if needed.
	* module.cc (trees_out::core_vals): Stream the new discriminator.
	(trees_in::core_vals): Likewise.
	* parser.cc (cp_parser_lambda_declarator_opt): Call
	record_lambda_scope_sig_discriminator.
	* pt.cc (tsubst_lambda_expr): Likewise.
	libcc1/
	* libcp1plugin.cc (plugin_start_lambda_closure_class_type):
	Initialize the per-scope, per-signature discriminator.
	gcc/testsuite/
	* g++.dg/abi/lambda-sig1-18.C: New.
	* g++.dg/abi/lambda-sig1-18vs17.C: New.
	* g++.dg/cpp1y/lambda-mangle-1-18.C: New.

1 files changed, 6 insertions, 1 deletions

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 4c0bacb..d13bb3d 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -1501,9 +1501,12 @@ enum cp_lambda_default_capture_mode_type {
   (((struct tree_lambda_expr *)LAMBDA_EXPR_CHECK (NODE))->extra_scope)
 
 /* Lambdas in the same extra scope might need a discriminating count.
-   This is a single per-scope count.  */
+   For ABI 17, we have single per-scope count, for ABI 18, we have
+   per-scope, per-signature numbering.  */
 #define LAMBDA_EXPR_SCOPE_ONLY_DISCRIMINATOR(NODE) \
   (((struct tree_lambda_expr *)LAMBDA_EXPR_CHECK (NODE))->discriminator_scope)
+#define LAMBDA_EXPR_SCOPE_SIG_DISCRIMINATOR(NODE) \
+  (((struct tree_lambda_expr *)LAMBDA_EXPR_CHECK (NODE))->discriminator_sig)
 
 /* During parsing of the lambda, a vector of capture proxies which need
    to be pushed once we're done processing a nested lambda.  */
@@ -1533,6 +1536,7 @@ struct GTY (()) tree_lambda_expr
   location_t locus;
   enum cp_lambda_default_capture_mode_type default_capture_mode : 2;
   unsigned discriminator_scope : 15; // Per-scope discriminator
+  unsigned discriminator_sig : 15; // Per-scope, per-signature discriminator
 };
 
 /* Non-zero if this template specialization has access violations that
@@ -7783,6 +7787,7 @@ extern void start_lambda_scope			(tree decl);
 extern void finish_lambda_scope			(void);
 extern void record_lambda_scope			(tree lambda);
 extern void record_lambda_scope_discriminator	(tree lambda);
+extern void record_lambda_scope_sig_discriminator (tree lambda, tree fn);
 extern tree start_lambda_function		(tree fn, tree lambda_expr);
 extern void finish_lambda_function		(tree body);
 extern bool regenerated_lambda_fn_p		(tree);