[PATCH] Fix failure building LLVM with location wrapper nodes (PR c++/83799)

[David Malcolm]

PR c++/83799 reports a failure building LLVM due to a bogus
"no matching function for call to" error at a callsite like this:
  TLI->getTypeLegalizationCost(DL);
where "DL" is from:
  using TargetTransformInfoImplBase::DL;

The root cause is that type_dependent_expression_p on a USING_DECL
should return true when processing a template, but after r256448 the
the argument at the callsite is a location wrapper around the USING_DECL,
and type_dependent_expression_p erroneously returns false for it, as
it is comparing tree codes, and failing a match, then looking at types.

This prevents cp_parser_postfix_expression from using the
"build_min_nt_call_vec" path for handling the call, instead erroneously
handling it via build_new_method_call (which fails for this case).

This patch fixes the problem by stripping any location wrappers before
the various tree code tests in type_dependent_expression_p.   It fixes
the reduced test case, and the full BasicTargetTransformInfo.ii; after
this patch, the assembly generated for that latter case is identical to
that generated before r256448.

Successfully bootstrapped&regrtested on x86_64-pc-linux-gnu.
Manually tested with "make s-selftest-c++" (since we don't run the
selftests for cc1plus by default).

OK for trunk?

gcc/cp/ChangeLog:
        PR c++/83799
        * pt.c (type_dependent_expression_p): Strip any location wrapper
        before testing tree codes.
        (selftest::test_type_dependent_expression_p): New function.
        (selftest::cp_pt_c_tests): Call it.

gcc/testsuite/ChangeLog:
        PR c++/83799
        * g++.dg/wrappers/pr83799.C: New test case.
---
 gcc/cp/pt.c                             | 28 ++++++++++++++++++++++++++++
 gcc/testsuite/g++.dg/wrappers/pr83799.C | 18 ++++++++++++++++++
 2 files changed, 46 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/wrappers/pr83799.C

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 4f8086b..9517fd9 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -24219,6 +24219,8 @@ type_dependent_expression_p (tree expression)
   if (expression == NULL_TREE || expression == error_mark_node)
     return false;
 
+  STRIP_ANY_LOCATION_WRAPPER (expression);
+
   /* An unresolved name is always dependent.  */
   if (identifier_p (expression)
       || TREE_CODE (expression) == USING_DECL
@@ -26657,12 +26659,38 @@ test_build_non_dependent_expr ()
             build_non_dependent_expr (wrapped_string_lit));
 }
 
+/* Verify that type_dependent_expression_p () works correctly, even
+   in the presence of location wrapper nodes.  */
+
+static void
+test_type_dependent_expression_p ()
+{
+  location_t loc = BUILTINS_LOCATION;
+
+  /* A USING_DECL in a template should be type-dependent, even if wrapped
+     with a location wrapper (PR c++/83799).  */
+
+  ++processing_template_decl;
+
+  tree name = get_identifier ("foo");
+  ASSERT_TRUE (type_dependent_expression_p (name));
+  tree using_decl = build_lang_decl (USING_DECL, name, NULL_TREE);
+  TREE_TYPE (using_decl) = integer_type_node;
+  ASSERT_TRUE (type_dependent_expression_p (using_decl));
+  tree wrapped_using_decl = maybe_wrap_with_location (using_decl, loc);
+  ASSERT_TRUE (location_wrapper_p (wrapped_using_decl));
+  ASSERT_TRUE (type_dependent_expression_p (wrapped_using_decl));
+
+  --processing_template_decl;
+}
+
 /* Run all of the selftests within this file.  */
 
 void
 cp_pt_c_tests ()
 {
   test_build_non_dependent_expr ();
+  test_type_dependent_expression_p ();
 }
 
 } // namespace selftest
diff --git a/gcc/testsuite/g++.dg/wrappers/pr83799.C 
b/gcc/testsuite/g++.dg/wrappers/pr83799.C
new file mode 100644
index 0000000..f93c0ae
--- /dev/null
+++ b/gcc/testsuite/g++.dg/wrappers/pr83799.C
@@ -0,0 +1,18 @@
+class DataLayout;
+class TargetLoweringBase {
+  void getTypeLegalizationCost(const DataLayout &DL) const;
+};
+class TargetTransformInfoImplBase {
+  const DataLayout &DL; // this line isn't actually needed to reproduce the 
issue
+};
+template <typename T>
+class TargetTransformInfoImplCRTPBase : public TargetTransformInfoImplBase {};
+template <typename T>
+class BasicTTIImplBase : public TargetTransformInfoImplCRTPBase<T> {
+  const TargetLoweringBase *getTLI() const;
+  using TargetTransformInfoImplBase::DL;
+  void getArithmeticInstrCost() {
+    const TargetLoweringBase *TLI = getTLI();
+    TLI->getTypeLegalizationCost(DL);
+  }
+};
-- 
1.8.5.3