On Thu, 2017-11-16 at 10:58 +0100, Richard Biener wrote:
> On Wed, Nov 15, 2017 at 4:33 PM, David Malcolm <dmalc...@redhat.com>
> wrote:
> > On Wed, 2017-11-15 at 12:11 +0100, Richard Biener wrote:
> > > On Wed, Nov 15, 2017 at 7:17 AM, Trevor Saunders <tbsaunde@tbsaun
> > > de.o
> > > rg> wrote:
> > > > On Fri, Nov 10, 2017 at 04:45:17PM -0500, David Malcolm wrote:
> > > > > This patch provides a mechanism in tree.c for adding a
> > > > > wrapper
> > > > > node
> > > > > for expressing a location_t, for those nodes for which
> > > > > !CAN_HAVE_LOCATION_P, along with a new method of cp_expr.
> > > > >
> > > > > It's called in later patches in the kit via that new method.
> > > > >
> > > > > In this version of the patch, I use NON_LVALUE_EXPR for
> > > > > wrapping
> > > > > constants, and VIEW_CONVERT_EXPR for other nodes.
> > > > >
> > > > > I also turned off wrapper nodes for EXCEPTIONAL_CLASS_P, for
> > > > > the
> > > > > sake
> > > > > of keeping the patch kit more minimal.
> > > > >
> > > > > The patch also adds a STRIP_ANY_LOCATION_WRAPPER macro for
> > > > > stripping
> > > > > such nodes, used later on in the patch kit.
> > > >
> > > > I happened to start reading this series near the end and was
> > > > rather
> > > > confused by this macro since it changes variables in a rather
> > > > unhygienic
> > > > way. Did you consider just defining a inline function to
> > > > return
> > > > the
> > > > actual decl? It seems like its not used that often so the
> > > > slight
> > > > extra
> > > > syntax should be that big a deal compared to the explicitness.
> > >
> > > Existing practice .... (STRIP_NOPS & friends). I'm fine either
> > > way,
> > > the patch looks good.
> > >
> > > Eventually you can simplify things by doing less checking in
> > > location_wrapper_p, like only checking
> > >
> > > +inline bool location_wrapper_p (const_tree exp)
> > > +{
> > > + if ((TREE_CODE (exp) == NON_LVALUE_EXPR
> > > + || (TREE_CODE (exp) == VIEW_CONVERT_EXPR
> > > + && (TREE_TYPE (exp)
> > > + == TREE_TYPE (TREE_OPERAND (exp, 0)))
> > > + return true;
> > > + return false;
> > > +}
> > >
> > > and renaming to maybe_location_wrapper_p. After all you can't
> > > really
> > > distinguish location wrappers from non-location wrappers? (and
> > > why
> > > would you want to?)
> >
> > That's the implementation I originally tried.
> >
> > As noted in an earlier thread about this, the problem I ran into
> > was
> > (in g++.dg/conversion/reinterpret1.C):
> >
> > // PR c++/15076
> >
> > struct Y { Y(int &); };
> >
> > int v;
> > Y y1(reinterpret_cast<int>(v)); // { dg-error "" }
> >
> > where the "reinterpret_cast<int>" has the same type as the VAR_DECL
> > v,
> > and hence the argument to y1 is a NON_LVALUE_EXPR around a
> > VAR_DECL,
> > where both have the same type, and hence location_wrapper_p () on
> > the
> > cast would return true.
> >
> > Compare with:
> >
> > Y y1(v);
> >
> > where the argument "v" with a location wrapper is a
> > VIEW_CONVERT_EXPR
> > around a VAR_DECL.
> >
> > With the simpler conditions you suggested above, both are treated
> > as
> > location wrappers (leading to the dg-error in the test failing),
> > whereas with the condition in the patch, only the latter is treated
> > as
> > a location wrapper, and an error is correctly emitted for the dg-
> > error.
> >
> > Hope this sounds sane. Maybe the function needs a more detailed
> > comment explaining this?
>
> Yes. I guess the above would argue for a new tree code but I can
> see that it is better to avoid that.
>
> Thanks,
> Richard.
[...]
Here's an updated version of the patch which:
* adds a much more detailed comment to location_wrapper_p,
* fixes an erroneous reference to LOCATION_WRAPPER_EXPR in the
comment to maybe_wrap_with_location (from an earlier unfinished
experiment)
* adds a selftest for handling wrapper nodes.
Is there consensus about whether this approach is sane? i.e.
* adding wrapper nodes via re-using existing tree codes (this kit), vs
* adding them via some new tree code ("LOCATION_WRAPPER_EXPR"?), vs
* the workaround of:
"[PATCH] C++: use an optional vec<location_t> for callsites"
https://gcc.gnu.org/ml/gcc-patches/2017-08/msg01392.html
Jason? Jakub? others?
(I'd like to get some version of this patch kit into gcc 8; I like
this kit's approach, as a minimal way to fix a real usability issue,
whilst giving us a route to doing more in gcc 9 (c.f. the v3 kit))
Thanks
Dave
gcc/ChangeLog:
PR c++/43486
* tree.c (maybe_wrap_with_location): New function.
(selftest::test_location_wrappers): New function.
(selftest::tree_c_tests): Call it.
* tree.h (STRIP_ANY_LOCATION_WRAPPER): New macro.
(maybe_wrap_with_location): New decl.
(location_wrapper_p): New inline function.
gcc/cp/ChangeLog:
PR c++/43486
* cp-tree.h (cp_expr::maybe_add_location_wrapper): New method.
---
gcc/cp/cp-tree.h | 6 ++++++
gcc/tree.c | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
gcc/tree.h | 42 ++++++++++++++++++++++++++++++++++++
3 files changed, 114 insertions(+)
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 4780df4..aa579a4 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -93,6 +93,12 @@ public:
set_location (make_location (m_loc, start, finish));
}
+ cp_expr& maybe_add_location_wrapper ()
+ {
+ m_value = maybe_wrap_with_location (m_value, m_loc);
+ return *this;
+ }
+
private:
tree m_value;
location_t m_loc;
diff --git a/gcc/tree.c b/gcc/tree.c
index 5416866..5e2b424 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -13791,6 +13791,38 @@ set_source_range (tree expr, source_range src_range)
return adhoc;
}
+/* Return EXPR, potentially wrapped with a node expression LOC,
+ if !CAN_HAVE_LOCATION_P (expr).
+
+ NON_LVALUE_EXPR is used for wrapping constants.
+ VIEW_CONVERT_EXPR is used for wrapping non-constants.
+
+ Wrapper nodes can be identified using location_wrapper_p. */
+
+tree
+maybe_wrap_with_location (tree expr, location_t loc)
+{
+ if (expr == NULL)
+ return NULL;
+ if (loc == UNKNOWN_LOCATION)
+ return expr;
+ if (CAN_HAVE_LOCATION_P (expr))
+ return expr;
+ /* We should only be adding wrappers for constants and for decls,
+ or for some exceptional tree nodes (e.g. BASELINK in the C++ FE). */
+ gcc_assert (CONSTANT_CLASS_P (expr)
+ || DECL_P (expr)
+ || EXCEPTIONAL_CLASS_P (expr));
+
+ if (EXCEPTIONAL_CLASS_P (expr))
+ return expr;
+
+ if (CONSTANT_CLASS_P (expr))
+ return build1_loc (loc, NON_LVALUE_EXPR, TREE_TYPE (expr), expr);
+ else
+ return build1_loc (loc, VIEW_CONVERT_EXPR, TREE_TYPE (expr), expr);
+}
+
/* Return the name of combined function FN, for debugging purposes. */
const char *
@@ -14016,6 +14048,39 @@ test_labels ()
ASSERT_FALSE (FORCED_LABEL (label_decl));
}
+/* Verify location wrappers. */
+
+static void
+test_location_wrappers ()
+{
+ location_t loc = BUILTINS_LOCATION;
+
+ /* Wrapping a constant. */
+ tree int_cst = build_int_cst (integer_type_node, 42);
+ ASSERT_FALSE (CAN_HAVE_LOCATION_P (int_cst));
+ ASSERT_FALSE (location_wrapper_p (int_cst));
+
+ tree wrapped_int_cst = maybe_wrap_with_location (int_cst, loc);
+ ASSERT_TRUE (location_wrapper_p (wrapped_int_cst));
+ ASSERT_EQ (loc, EXPR_LOCATION (wrapped_int_cst));
+
+ /* Wrapping a variable. */
+ tree int_var = build_decl (UNKNOWN_LOCATION, VAR_DECL,
+ get_identifier ("some_int_var"),
+ integer_type_node);
+ ASSERT_FALSE (CAN_HAVE_LOCATION_P (int_var));
+ ASSERT_FALSE (location_wrapper_p (int_var));
+
+ tree wrapped_int_var = maybe_wrap_with_location (int_var, loc);
+ ASSERT_TRUE (location_wrapper_p (wrapped_int_var));
+ ASSERT_EQ (loc, EXPR_LOCATION (wrapped_int_var));
+
+ /* Verify that "reinterpret_cast<int>(some_int_var)" is not a location
+ wrapper. */
+ tree r_cast = build1 (NON_LVALUE_EXPR, integer_type_node, int_var);
+ ASSERT_FALSE (location_wrapper_p (r_cast));
+}
+
/* Run all of the selftests within this file. */
void
@@ -14024,6 +14089,7 @@ tree_c_tests ()
test_integer_constants ();
test_identifiers ();
test_labels ();
+ test_location_wrappers ();
}
} // namespace selftest
diff --git a/gcc/tree.h b/gcc/tree.h
index db67858..112471b 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -483,6 +483,15 @@ extern void omp_clause_range_check_failed (const_tree,
const char *, int,
#define STRIP_USELESS_TYPE_CONVERSION(EXP) \
(EXP) = tree_ssa_strip_useless_type_conversions (EXP)
+/* Remove any VIEW_CONVERT_EXPR or NON_LVALUE_EXPR that's purely
+ in use to provide a location_t. */
+
+#define STRIP_ANY_LOCATION_WRAPPER(EXP) \
+ do { \
+ if (location_wrapper_p (EXP)) \
+ (EXP) = TREE_OPERAND ((EXP), 0); \
+ } while (0)
+
/* Nonzero if TYPE represents a vector type. */
#define VECTOR_TYPE_P(TYPE) (TREE_CODE (TYPE) == VECTOR_TYPE)
@@ -1146,6 +1155,8 @@ get_expr_source_range (tree expr)
extern void protected_set_expr_location (tree, location_t);
+extern tree maybe_wrap_with_location (tree, location_t);
+
/* In a TARGET_EXPR node. */
#define TARGET_EXPR_SLOT(NODE) TREE_OPERAND_CHECK_CODE (NODE, TARGET_EXPR, 0)
#define TARGET_EXPR_INITIAL(NODE) TREE_OPERAND_CHECK_CODE (NODE, TARGET_EXPR,
1)
@@ -3643,6 +3654,37 @@ id_equal (const char *str, const_tree id)
return !strcmp (str, IDENTIFIER_POINTER (id));
}
+/* Test if EXP is merely a wrapper node, added to express a location_t
+ on behalf of the node's child (e.g. by maybe_wrap_with_location).
+
+ A wrapper node has code NON_LVALUE_EXPR or VIEW_CONVERT_EXPR, and the
+ same type as its operand.
+
+ NON_LVALUE_EXPR is used for wrapping constants.
+ VIEW_CONVERT_EXPR is used for wrapping non-constants.
+
+ A subtlety is that we have to test whether we have the correct
+ TREE_CODE for the wrapped TREE_CODE. Otherwise, e.g. the C++ expression:
+ reinterpret_cast<int>(some_int_var)
+ is a NON_LVALUE_EXPR around a non-constant of the same type, and
+ could thus be mischaracterized as a location wrapper node.
+
+ Hence we need to check CONSTANT_CLASS_P (TREE_OPERAND (EXP, 0))
+ and check for the corresponding NON_LVALUE_EXPR or VIEW_CONVERT_EXPR
+ for EXP to be a wrapper. */
+
+inline bool location_wrapper_p (const_tree exp)
+{
+ if (((TREE_CODE (exp) == NON_LVALUE_EXPR
+ && CONSTANT_CLASS_P (TREE_OPERAND (exp, 0)))
+ || (TREE_CODE (exp) == VIEW_CONVERT_EXPR
+ && !CONSTANT_CLASS_P (TREE_OPERAND (exp, 0))))
+ && (TREE_TYPE (exp)
+ == TREE_TYPE (TREE_OPERAND (exp, 0))))
+ return true;
+ return false;
+}
+
#define error_mark_node global_trees[TI_ERROR_MARK]
#define intQI_type_node global_trees[TI_INTQI_TYPE]
--
1.8.5.3
