The following fixes a long-standing bug with DSE removing stores as
dead even though they are live across non-call exceptional flow.
This affects both GIMPLE and RTL DSE and the fix is similar in
making externally throwing statements uses of non-local stores.
Note this doesn't fix the GIMPLE side when the throwing statement
does not involve a load or a store because then the statement does
not have virtual operands and thus is not visited by GIMPLE DSE.
Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.
This doesn't seem to be a regression and I'm unsure as to how
important it is for Ada (I consider it not important for C/C++),
so for now I'll queue it for next stage1.
PR middle-end/106075
* dse.cc (scan_insn): Consider externally throwing insns
to read from not frame based memory.
* tree-ssa-dse.cc (dse_classify_store): Consider externally
throwing uses to read from global memory.
* gcc.dg/torture/pr106075-1.c: New testcase.
---
gcc/dse.cc | 5 ++++
gcc/testsuite/gcc.dg/torture/pr106075-1.c | 36 +++++++++++++++++++++++
gcc/tree-ssa-dse.cc | 8 ++++-
3 files changed, 48 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/gcc.dg/torture/pr106075-1.c
diff --git a/gcc/dse.cc b/gcc/dse.cc
index a2db8d1cc32..7e258b81f66 100644
--- a/gcc/dse.cc
+++ b/gcc/dse.cc
@@ -2633,6 +2633,11 @@ scan_insn (bb_info_t bb_info, rtx_insn *insn, int
max_active_local_stores)
return;
}
+ /* An externally throwing statement may read any memory that is not
+ relative to the frame. */
+ if (can_throw_external (insn))
+ add_non_frame_wild_read (bb_info);
+
/* Assuming that there are sets in these insns, we cannot delete
them. */
if ((GET_CODE (PATTERN (insn)) == CLOBBER)
diff --git a/gcc/testsuite/gcc.dg/torture/pr106075-1.c
b/gcc/testsuite/gcc.dg/torture/pr106075-1.c
new file mode 100644
index 00000000000..b9affbf1082
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr106075-1.c
@@ -0,0 +1,36 @@
+/* { dg-do run { target *-*-linux* } } */
+/* { dg-additional-options "-fnon-call-exceptions" } */
+
+#include <unistd.h>
+#include <signal.h>
+#include <stdlib.h>
+
+int a = 1;
+short *b;
+void __attribute__((noipa))
+test()
+{
+ a=12345;
+ *b=0;
+ a=1;
+}
+
+void check (int i)
+{
+ if (a != 12345)
+ abort ();
+ exit (0);
+}
+
+int
+main ()
+{
+ struct sigaction s;
+ sigemptyset (&s.sa_mask);
+ s.sa_handler = check;
+ s.sa_flags = 0;
+ sigaction (SIGSEGV, &s, NULL);
+ test();
+ abort ();
+ return 0;
+}
diff --git a/gcc/tree-ssa-dse.cc b/gcc/tree-ssa-dse.cc
index 46ab57d5754..b2e2359c3da 100644
--- a/gcc/tree-ssa-dse.cc
+++ b/gcc/tree-ssa-dse.cc
@@ -960,6 +960,7 @@ dse_classify_store (ao_ref *ref, gimple *stmt,
auto_bitmap visited;
std::unique_ptr<data_reference, void(*)(data_reference_p)>
dra (nullptr, free_data_ref);
+ bool maybe_global = ref_may_alias_global_p (ref, false);
if (by_clobber_p)
*by_clobber_p = true;
@@ -1038,6 +1039,11 @@ dse_classify_store (ao_ref *ref, gimple *stmt,
last_phi_def = as_a <gphi *> (use_stmt);
}
}
+ /* If the stmt can throw externally and the store is
+ visible in the context unwound to the store is live. */
+ else if (maybe_global
+ && stmt_can_throw_external (cfun, use_stmt))
+ return DSE_STORE_LIVE;
/* If the statement is a use the store is not dead. */
else if (ref_maybe_used_by_stmt_p (use_stmt, ref))
{
@@ -1116,7 +1122,7 @@ dse_classify_store (ao_ref *ref, gimple *stmt,
just pretend the stmt makes itself dead. Otherwise fail. */
if (defs.is_empty ())
{
- if (ref_may_alias_global_p (ref, false))
+ if (maybe_global)
return DSE_STORE_LIVE;
if (by_clobber_p)
--
2.35.3
