From 2b0e81d5cc2f7e1d773f6c502bd65b097f392675 Mon Sep 17 00:00:00 2001
From: Nathan Sidwell <nathan@acm.org>
Date: Mon, 31 Oct 2022 06:11:28 -0400
Subject: 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.
---
 gcc/cp/pt.cc | 1 +
 1 file changed, 1 insertion(+)

(limited to 'gcc/cp/pt.cc')

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index fc6279c..c3fc56a 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -19912,6 +19912,7 @@ tsubst_lambda_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl)
 	  goto out;
 	}
       finish_member_declaration (inst);
+      record_lambda_scope_sig_discriminator (r, inst);
 
       tree fn = oldtmpl ? DECL_TEMPLATE_RESULT (inst) : inst;
 
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