[PATCH] tree-optimization/108691 - remove trigger-happy assert

[PATCH] tree-optimization/108691 - remove trigger-happy assert

[Richard Biener]

The following gets rid of the idea that we should prevent setjmp
like calls from popping up in uncontrolled way in the IL for now.
The solution is probably to handle it similar as noreturn has
the ctrl-altering flag on stmts, but use another flag, for example
ctrl-receiving which would also make sure the stmt is first.

Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.

OK?

	PR tree-optimization/108691
	* tree-ssa-dce.cc (eliminate_unnecessary_stmts): Remove
	assert about calls_setjmp not becoming true when it was false.

	* gcc.dg/pr108691.c: New testcase.
---
 gcc/testsuite/gcc.dg/pr108691.c | 9 +++++++++
 gcc/tree-ssa-dce.cc             | 8 +++++---
 2 files changed, 14 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/pr108691.c

diff --git a/gcc/testsuite/gcc.dg/pr108691.c b/gcc/testsuite/gcc.dg/pr108691.c
new file mode 100644
index 00000000000..e412df10f22
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr108691.c
@@ -0,0 +1,9 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+extern int __attribute__((returns_twice)) setjmp(void*);
+
+void bbb(void) {
+  int (*fnptr)(void*) = setjmp;
+  fnptr(0);
+}
diff --git a/gcc/tree-ssa-dce.cc b/gcc/tree-ssa-dce.cc
index ceeb0ad5ab3..0ae998f86f9 100644
--- a/gcc/tree-ssa-dce.cc
+++ b/gcc/tree-ssa-dce.cc
@@ -1512,10 +1512,12 @@ eliminate_unnecessary_stmts (bool aggressive)
 	remove_edge (to_remove_edges[i]);
       cfg_altered = true;
     }
-  /* When we cleared calls_setjmp we can purge all abnormal edges.  Do so.  */
-  if (cfun->calls_setjmp != had_setjmp)
+  /* When we cleared calls_setjmp we can purge all abnormal edges.  Do so.
+     ???  We'd like to assert that setjmp calls do not pop out of nothing
+     but we currently lack a per-stmt way of noting whether a call was
+     recognized as returns-twice (or rather receives-control).  */
+  if (!cfun->calls_setjmp && had_setjmp)
     {
-      gcc_assert (!cfun->calls_setjmp);
       /* Make sure we only remove the edges, not dominated blocks.  Using
 	 gimple_purge_dead_abnormal_call_edges would do that and we
 	 cannot free dominators yet.  */
-- 
2.35.3

Re: [PATCH] tree-optimization/108691 - remove trigger-happy assert

[Jakub Jelinek]

On Tue, Feb 21, 2023 at 01:47:59PM +0100, Richard Biener wrote:
> The following gets rid of the idea that we should prevent setjmp
> like calls from popping up in uncontrolled way in the IL for now.
> The solution is probably to handle it similar as noreturn has
> the ctrl-altering flag on stmts, but use another flag, for example
> ctrl-receiving which would also make sure the stmt is first.

Yes, I'm all for it.
> 
> Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.
> 
> OK?
> 
> 	PR tree-optimization/108691
> 	* tree-ssa-dce.cc (eliminate_unnecessary_stmts): Remove
> 	assert about calls_setjmp not becoming true when it was false.
> 
> 	* gcc.dg/pr108691.c: New testcase.

Ok.

	Jakub