[pushed] c++: fix 32-bit spaceship failures [PR110185]

[pushed] c++: fix 32-bit spaceship failures [PR110185]

[Jason Merrill]

Tested x86_64-pc-linux-gnu, applying to trunk.

-- 8< --

Various spaceship tests failed after r14-1624.  This turned out to be
because the comparison category classes return in memory on 32-bit targets,
and the synthesized operator<=> looks something like

if (auto v = a.x <=> b.x, v == 0); else return v;
if (auto v = a.y <=> b.y, v == 0); else return v;
etc.

so check_return_expr was trying to do NRVO for all the 'v' variables, and
now on subsequent returns we check to see if the previous NRV is still in
scope.  But the NRVs didn't have names, so looking up name bindings crashed.
Fixed both by giving 'v' a name so we can NRVO the first one, and fixing the
test to give up if the old NRV has no name.

	PR c++/110185
	PR c++/58487

gcc/cp/ChangeLog:

	* method.cc (build_comparison_op): Give retval a name.
	* typeck.cc (check_return_expr): Fix for nameless variables.
---
 gcc/cp/method.cc | 1 +
 gcc/cp/typeck.cc | 1 +
 2 files changed, 2 insertions(+)

diff --git a/gcc/cp/method.cc b/gcc/cp/method.cc
index 0c2ca9e4f41..91cf943f110 100644
--- a/gcc/cp/method.cc
+++ b/gcc/cp/method.cc
@@ -1679,6 +1679,7 @@ build_comparison_op (tree fndecl, bool defining, tsubst_flags_t complain)
 	      if (defining)
 		{
 		  tree var = create_temporary_var (rettype);
+		  DECL_NAME (var) = get_identifier ("retval");
 		  pushdecl (var);
 		  cp_finish_decl (var, comp, false, NULL_TREE, flags);
 		  comp = retval = var;
diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc
index 11927cbdf83..da591dafc8f 100644
--- a/gcc/cp/typeck.cc
+++ b/gcc/cp/typeck.cc
@@ -11174,6 +11174,7 @@ check_return_expr (tree retval, bool *no_warning)
 	current_function_return_value = bare_retval;
       else if (current_function_return_value
 	       && VAR_P (current_function_return_value)
+	       && DECL_NAME (current_function_return_value)
 	       && !decl_in_scope_p (current_function_return_value))
 	{
 	  /* The earlier NRV is out of scope at this point, so it's safe to

base-commit: 3e12669a0eb968cfcbe9242b382fd8020935edf8
prerequisite-patch-id: c69d648e8ed235e699b6a36b3cfbc031dc37fca0
prerequisite-patch-id: f01eb83e6402e182a0c9bd6202e4ed6db7529733
-- 
2.31.1