As I was discussing with richi, I don't think it makes sense to protect
calls to pure/const functions from DCE just because they aren't explicitly
declared noexcept. PR100382 indicates that there are different
considerations for Go, which has non-call exceptions. But still turn the
flag off for that specific testcase.
Tested x86_64-pc-linux-gnu, applying to trunk.
gcc/c-family/ChangeLog:
* c-opts.c (c_common_post_options): Set -fdelete-dead-exceptions.
---
gcc/doc/invoke.texi | 6 ++++--
gcc/c-family/c-opts.c | 4 ++++
gcc/testsuite/g++.dg/torture/pr100382.C | 1 +
3 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index e67d47af676..ea8812425e9 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -16335,8 +16335,10 @@ arbitrary signal handlers such as @code{SIGALRM}.
@opindex fdelete-dead-exceptions
Consider that instructions that may throw exceptions but don't otherwise
contribute to the execution of the program can be optimized away.
-This option is enabled by default for the Ada compiler, as permitted by
-the Ada language specification.
+This does not affect calls to functions except those with the
+@code{pure} or @code{const} attributes.
+This option is enabled by default for the Ada and C++ compilers, as permitted
by
+the language specifications.
Optimization passes that cause dead exceptions to be removed are enabled
independently at different optimization levels.
@item -funwind-tables
diff --git a/gcc/c-family/c-opts.c b/gcc/c-family/c-opts.c
index 60b5802722c..1212edd1b28 100644
--- a/gcc/c-family/c-opts.c
+++ b/gcc/c-family/c-opts.c
@@ -1015,6 +1015,10 @@ c_common_post_options (const char **pfilename)
SET_OPTION_IF_UNSET (&global_options, &global_options_set, flag_finite_loops,
optimize >= 2 && cxx_dialect >= cxx11);
+ /* It's OK to discard calls to pure/const functions that throw. */
+ SET_OPTION_IF_UNSET (&global_options, &global_options_set,
+ flag_delete_dead_exceptions, true);
+
if (cxx_dialect >= cxx11)
{
/* If we're allowing C++0x constructs, don't warn about C++98
diff --git a/gcc/testsuite/g++.dg/torture/pr100382.C
b/gcc/testsuite/g++.dg/torture/pr100382.C
index ffc4182cfce..eac5743b956 100644
--- a/gcc/testsuite/g++.dg/torture/pr100382.C
+++ b/gcc/testsuite/g++.dg/torture/pr100382.C
@@ -1,4 +1,5 @@
// { dg-do run }
+// { dg-additional-options -fno-delete-dead-exceptions }
int x, y;
int __attribute__((pure,noinline)) foo () { if (x) throw 1; return y; }
base-commit: 6d1cdb27828d2ef1ae1ab0209836646a269b9610
--
2.27.0
