https://gcc.gnu.org/g:7f5adfd31b3af08924faec36679eaea40a98af19
commit r15-6944-g7f5adfd31b3af08924faec36679eaea40a98af19
Author: Jakub Jelinek <ja...@redhat.com>
Date: Thu Jan 16 09:25:16 2025 +0100
tree-ssa-propagate: Special case lhs of musttail calls in
may_propagate_copy [PR118430]
This patch ensures that VRP or similar passes don't replace the uses of lhs
of
[[gnu::musttail]] calls with some constant (e.g. if the call is known is
known
to return a singleton value range) etc. to make it more likely that it is
actually
tail callable.
2025-01-16 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.
Diff:
---
gcc/testsuite/c-c++-common/musttail14.c | 6 +++---
gcc/tree-ssa-propagate.cc | 9 ++++++++-
2 files changed, 11 insertions(+), 4 deletions(-)
diff --git a/gcc/testsuite/c-c++-common/musttail14.c
b/gcc/testsuite/c-c++-common/musttail14.c
index e2ab20bc5a46..e95bc9bc7688 100644
--- a/gcc/testsuite/c-c++-common/musttail14.c
+++ b/gcc/testsuite/c-c++-common/musttail14.c
@@ -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)
diff --git a/gcc/tree-ssa-propagate.cc b/gcc/tree-ssa-propagate.cc
index 94d4401f54af..ec2068948215 100644
--- a/gcc/tree-ssa-propagate.cc
+++ b/gcc/tree-ssa-propagate.cc
@@ -870,7 +870,7 @@ substitute_and_fold_dom_walker::before_dom_children
(basic_block bb)
}
/* 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, bool
dest_not_abnormal_phi_edge_p)
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;
}
