__builtin_stack_save can be removed when the lhs becomes unused
as it is just recording the current StackPointer into another register.
Bootstrapped and tested on x86_64-linux-gnu.
PR tree-optimization/122037
gcc/ChangeLog:
* tree-ssa-dce.cc (eliminate_unnecessary_stmts): Remove
__builtin_stack_save when the lhs is unused.
gcc/testsuite/ChangeLog:
* gcc.dg/tree-ssa/vla-1.c: New test.
Signed-off-by: Andrew Pinski <[email protected]>
---
gcc/testsuite/gcc.dg/tree-ssa/vla-1.c | 15 +++++++++++++++
gcc/tree-ssa-dce.cc | 5 ++++-
2 files changed, 19 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/vla-1.c
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/vla-1.c
b/gcc/testsuite/gcc.dg/tree-ssa/vla-1.c
new file mode 100644
index 00000000000..37b75142407
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/vla-1.c
@@ -0,0 +1,15 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized -fdump-tree-cddce1-details" } */
+/* PR tree-optimization/122037 */
+
+void bar1 (char *, int) __attribute__((noreturn));
+void foo1 (int size)
+{
+ char temp[size];
+ temp[size-1] = '\0';
+ bar1 (temp, size);
+}
+
+/* The call to __builtin_stack_save should have been removed. */
+/* { dg-final { scan-tree-dump "Deleting : __builtin_stack_save" "cddce1" } }
*/
+/* { dg-final { scan-tree-dump-not "__builtin_stack_save " "optimized" } } */
diff --git a/gcc/tree-ssa-dce.cc b/gcc/tree-ssa-dce.cc
index 43869088322..160c28cb807 100644
--- a/gcc/tree-ssa-dce.cc
+++ b/gcc/tree-ssa-dce.cc
@@ -1682,9 +1682,12 @@ eliminate_unnecessary_stmts (bool aggressive)
update_stmt (call_stmt);
release_ssa_name (name);
+ /* __builtin_stack_save without lhs is not needed. */
+ if (gimple_call_builtin_p (call_stmt, BUILT_IN_STACK_SAVE))
+ remove_dead_stmt (&gsi, bb, to_remove_edges);
/* GOMP_SIMD_LANE (unless three argument) or ASAN_POISON
without lhs is not needed. */
- if (gimple_call_internal_p (call_stmt))
+ else if (gimple_call_internal_p (call_stmt))
switch (gimple_call_internal_fn (call_stmt))
{
case IFN_GOMP_SIMD_LANE:
--
2.43.0
