When DCE removes the lhs of __builtin_stack_save, we can also
remove the function itself. This adds that to gimple fold.
Bootstrapped and tested on x86_64-linux-gnu.
PR tree-optimization/122037
gcc/ChangeLog:
* gimple-fold.cc (gimple_fold_builtin_stack_save): New function.
(gimple_fold_builtin): Call gimple_fold_builtin_stack_save
for __builtin_stack_save.
gcc/testsuite/ChangeLog:
* gcc.dg/tree-ssa/vla-1.c: New test.
Signed-off-by: Andrew Pinski <[email protected]>
---
gcc/gimple-fold.cc | 21 +++++++++++++++++++++
gcc/testsuite/gcc.dg/tree-ssa/vla-1.c | 14 ++++++++++++++
2 files changed, 35 insertions(+)
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/vla-1.c
diff --git a/gcc/gimple-fold.cc b/gcc/gimple-fold.cc
index edcc04adc08..5f88cce7760 100644
--- a/gcc/gimple-fold.cc
+++ b/gcc/gimple-fold.cc
@@ -5372,6 +5372,25 @@ gimple_fold_builtin_stdarg (gimple_stmt_iterator *gsi,
gcall *call)
}
}
+/* Fold __builtin_stack_save if possible. Returns true if it was folded.
+ Currently this removes the call if the lhs is unused. */
+static bool
+gimple_fold_builtin_stack_save (gimple_stmt_iterator *gsi, gcall *call)
+{
+ if (gimple_call_num_args (call) != 0)
+ return false;
+
+ if (gimple_call_lhs (call))
+ return false;
+
+ // Remove the call since the result is unused.
+ unlink_stmt_vdef (call);
+ release_defs (call);
+ gsi_replace (gsi, gimple_build_nop (), true);
+
+ return true;
+}
+
/* Fold the non-target builtin at *GSI and return whether any simplification
was made. */
@@ -5390,6 +5409,8 @@ gimple_fold_builtin (gimple_stmt_iterator *gsi)
enum built_in_function fcode = DECL_FUNCTION_CODE (callee);
switch (fcode)
{
+ case BUILT_IN_STACK_SAVE:
+ return gimple_fold_builtin_stack_save (gsi, stmt);
case BUILT_IN_VA_START:
case BUILT_IN_VA_END:
case BUILT_IN_VA_COPY:
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..ec19babebc4
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/vla-1.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* 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-not "__builtin_stack_save " "optimized" } } */
--
2.43.0
