Hi!
Here is a version of the c_update_type_canonical fixes which passed
bootstrap/regtest.
The non-trivial part is the handling of the case when
build_qualified_type (TYPE_CANONICAL (t), TYPE_QUALS (x))
returns a type with NULL TYPE_CANONICAL. That should happen only
if TYPE_CANONICAL (t) == t, because otherwise c_update_type_canonical should
have been already called on the other type. c, the returned type, is usually x
and in that case it should have TYPE_CANONICAL set to itself, or worst
for whatever reason x is not the right canonical type (say it has attributes
or whatever disqualifies it from check_qualified_type). In that case
either it finds some pre-existing type from the variant chain of t which
is later in the chain and we haven't processed it yet (but then
get_qualified_type moves it right after t in:
/* Put the found variant at the head of the variant list so
frequently searched variants get found faster. The C++ FE
benefits greatly from this. */
tree t = *tp;
*tp = TYPE_NEXT_VARIANT (t);
TYPE_NEXT_VARIANT (t) = TYPE_NEXT_VARIANT (mv);
TYPE_NEXT_VARIANT (mv) = t;
return t;
optimization), or creates a fresh new type using build_variant_type_copy,
which again places the new type right after t:
/* Add the new type to the chain of variants of TYPE. */
TYPE_NEXT_VARIANT (t) = TYPE_NEXT_VARIANT (m);
TYPE_NEXT_VARIANT (m) = t;
TYPE_MAIN_VARIANT (t) = m;
At this point we want to make c its own canonical type (i.e. TYPE_CANONICAL
(c) = c;), but also need to process pointers to it and only then return back
to processing x. Processing the whole chain from c again could be costly,
we could have hundreds of types in the chain already processed, and while
the loop would just quickly skip them
for (tree x = t, l = NULL_TREE; x; l = x, x = TYPE_NEXT_VARIANT (x))
{
if (x != t && TYPE_STRUCTURAL_EQUALITY_P (x))
...
else if (x != t)
continue;
it feels costly. So, this patch instead moves c from right after t
to right before x in the chain (that shouldn't change anything, because
clearly build_qualified_type didn't find any matches in the chain before
x) and continues processing the c at that position, so should handle the
x that encountered this in the next iteration.
We could avoid some of the moving in the chain if we processed the chain
twice, once deal only with x != t && TYPE_STRUCTURAL_EQUALITY_P (x)
&& TYPE_CANONICAL (t) == t && check_qualified_type (t, x, TYPE_QUALS (x))
types (in that case set TYPE_CANONICAL (x) = x) and once the rest. There
is still the theoretical case where build_qualified_type would return
a new type and in that case we are back to the moving the type around and
needing to handle it though.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2024-06-19 Jakub Jelinek <ja...@redhat.com>
Martin Uecker <uec...@tugraz.at>
PR c/114930
PR c/115502
gcc/c/
* c-decl.cc (c_update_type_canonical): Assert t is main variant
with 0 TYPE_QUALS. Simplify and don't use check_qualified_type.
Deal with the case where build_qualified_type returns
TYPE_STRUCTURAL_EQUALITY_P type.
gcc/testsuite/
* gcc.dg/pr114574-1.c: Require lto effective target.
* gcc.dg/pr114574-2.c: Likewise.
* gcc.dg/pr114930.c: New test.
* gcc.dg/pr115502.c: New test.
--- gcc/c/c-decl.cc.jj 2024-06-07 12:17:09.582969919 +0200
+++ gcc/c/c-decl.cc 2024-06-19 21:06:59.863496408 +0200
@@ -9367,18 +9367,42 @@ is_flexible_array_member_p (bool is_last
static void
c_update_type_canonical (tree t)
{
- for (tree x = TYPE_MAIN_VARIANT (t); x; x = TYPE_NEXT_VARIANT (x))
+ gcc_checking_assert (TYPE_MAIN_VARIANT (t) == t && !TYPE_QUALS (t));
+ for (tree x = t, l = NULL_TREE; x; l = x, x = TYPE_NEXT_VARIANT (x))
{
if (x != t && TYPE_STRUCTURAL_EQUALITY_P (x))
{
- if (TYPE_QUALS (x) == TYPE_QUALS (t))
+ if (!TYPE_QUALS (x))
TYPE_CANONICAL (x) = TYPE_CANONICAL (t);
- else if (TYPE_CANONICAL (t) != t
- || check_qualified_type (x, t, TYPE_QUALS (x)))
- TYPE_CANONICAL (x)
- = build_qualified_type (TYPE_CANONICAL (t), TYPE_QUALS (x));
else
- TYPE_CANONICAL (x) = x;
+ {
+ tree
+ c = build_qualified_type (TYPE_CANONICAL (t), TYPE_QUALS (x));
+ if (TYPE_STRUCTURAL_EQUALITY_P (c))
+ {
+ gcc_checking_assert (TYPE_CANONICAL (t) == t);
+ if (c == x)
+ TYPE_CANONICAL (x) = x;
+ else
+ {
+ /* build_qualified_type for this function unhelpfully
+ moved c from some later spot in TYPE_MAIN_VARIANT (t)
+ chain to right after t (or created it there). Move
+ it right before x and process c and then x. */
+ gcc_checking_assert (TYPE_NEXT_VARIANT (t) == c);
+ if (l != t)
+ {
+ TYPE_NEXT_VARIANT (t) = TYPE_NEXT_VARIANT (c);
+ TYPE_NEXT_VARIANT (l) = c;
+ TYPE_NEXT_VARIANT (c) = x;
+ }
+ TYPE_CANONICAL (c) = c;
+ x = c;
+ }
+ }
+ else
+ TYPE_CANONICAL (x) = TYPE_CANONICAL (c);
+ }
}
else if (x != t)
continue;
--- gcc/testsuite/gcc.dg/pr114574-1.c.jj 2024-04-20 00:05:07.273690453
+0200
+++ gcc/testsuite/gcc.dg/pr114574-1.c 2024-06-19 20:00:33.015984692 +0200
@@ -1,6 +1,6 @@
-/* PR lto/114574
- * { dg-do compile }
- * { dg-options "-flto" } */
+/* PR lto/114574 */
+/* { dg-do compile { target lto } } */
+/* { dg-options "-flto" } */
const struct S * x;
struct S {};
--- gcc/testsuite/gcc.dg/pr114574-2.c.jj 2024-04-20 00:05:07.274690440
+0200
+++ gcc/testsuite/gcc.dg/pr114574-2.c 2024-06-19 20:00:55.084704278 +0200
@@ -1,6 +1,6 @@
-/* PR lto/114574
- * { dg-do compile }
- * { dg-options "-flto -std=c23" } */
+/* PR lto/114574 */
+/* { dg-do compile { target lto } } */
+/* { dg-options "-flto -std=c23" } */
const struct S * x;
struct S {};
--- gcc/testsuite/gcc.dg/pr114930.c.jj 2024-06-18 21:27:53.782729543 +0200
+++ gcc/testsuite/gcc.dg/pr114930.c 2024-06-18 21:27:53.782729543 +0200
@@ -0,0 +1,9 @@
+/* PR c/114930 */
+/* { dg-do compile { target lto } } */
+/* { dg-options "-std=c23 -flto" } */
+
+typedef struct WebPPicture WebPPicture;
+typedef int (*WebPProgressHook)(const WebPPicture *);
+WebPProgressHook progress_hook;
+struct WebPPicture {
+} WebPGetColorPalette(const struct WebPPicture *);
--- gcc/testsuite/gcc.dg/pr115502.c.jj 2024-06-18 21:27:53.793729408 +0200
+++ gcc/testsuite/gcc.dg/pr115502.c 2024-06-18 21:27:53.793729408 +0200
@@ -0,0 +1,9 @@
+/* PR c/115502 */
+/* { dg-do compile { target lto } } */
+/* { dg-options "-std=c23 -flto" } */
+
+typedef struct _OSet OSet;
+typedef OSet AvlTree;
+void vgPlain_OSetGen_Lookup(const OSet *);
+struct _OSet {};
+void vgPlain_OSetGen_Lookup(const AvlTree *);
Jakub
