Hi!
And here is incremental (for now tested just on the new testcases)
patch to avoid VRP etc. to replace lhs of musttail call with something else.
2025-01-15 Jakub Jelinek <ja...@redhat.com>
PR tree-optimization/118430
* tree-ssa-propagate.cc (may_propagate_copy): Return false if dest
is lhs of an [[gnu::musttail]] call.
(substitute_and_fold_dom_walker::before_dom_children): Formatting fix.
* c-c++-common/musttail14.c: Expect lhs on the must tail call calls.
--- gcc/tree-ssa-propagate.cc.jj 2025-01-02 11:23:02.000000000 +0100
+++ gcc/tree-ssa-propagate.cc 2025-01-15 11:34:38.554602529 +0100
@@ -870,7 +870,7 @@ substitute_and_fold_dom_walker::before_d
}
/* Also fold if we want to fold all statements. */
else if (substitute_and_fold_engine->fold_all_stmts
- && fold_stmt (&i, follow_single_use_edges))
+ && fold_stmt (&i, follow_single_use_edges))
{
did_replace = true;
stmt = gsi_stmt (i);
@@ -1081,6 +1081,13 @@ may_propagate_copy (tree dest, tree orig
if (TREE_CODE (dest) == SSA_NAME && virtual_operand_p (dest))
return false;
+ /* Keep lhs of [[gnu::musttail]] calls as is, those need to be still
+ tail callable. */
+ if (TREE_CODE (dest) == SSA_NAME
+ && is_gimple_call (SSA_NAME_DEF_STMT (dest))
+ && gimple_call_must_tail_p (as_a <gcall *> (SSA_NAME_DEF_STMT (dest))))
+ return false;
+
/* Anything else is OK. */
return true;
}
--- gcc/testsuite/c-c++-common/musttail14.c.jj 2025-01-15 11:32:58.048016223
+0100
+++ gcc/testsuite/c-c++-common/musttail14.c 2025-01-15 11:33:30.982552975
+0100
@@ -1,9 +1,9 @@
/* PR tree-optimization/118430 */
/* { dg-do compile { target musttail } } */
/* { dg-options "-O2 -fdump-tree-optimized" } */
-/* { dg-final { scan-tree-dump-times " bar \\\(\[^\n\r]\*\\\); \\\[tail
call\\\] \\\[must tail call\\\]" 1 "optimized" } } */
-/* { dg-final { scan-tree-dump-times " freddy \\\(\[^\n\r]\*\\\); \\\[tail
call\\\] \\\[must tail call\\\]" 1 "optimized" } } */
-/* { dg-final { scan-tree-dump-times " (?:bar|freddy) \\\(\[^\n\r]\*\\\);
\\\[tail call\\\]" 2 "optimized" } } */
+/* { dg-final { scan-tree-dump-times " \[^\n\r]* = bar \\\(\[^\n\r]\*\\\);
\\\[tail call\\\] \\\[must tail call\\\]" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times " \[^\n\r]* = freddy \\\(\[^\n\r]\*\\\);
\\\[tail call\\\] \\\[must tail call\\\]" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-not " (?:bar|freddy) \\\(\[^\n\r]\*\\\);
\\\[tail call\\\]" "optimized" } } */
__attribute__ ((noipa)) void
foo (int x)
Jakub
