On 11/25/2021 6:33 AM, Richard Biener via Gcc-patches wrote:
It seems to be a style to place gcc_unreachable () after a
switch that handles all cases with every case returning.
Those are unreachable (well, yes!), so they will be elided
at CFG construction time and the middle-end will place
another __builtin_unreachable "after" them to note the
path doesn't lead to a return when the function is not declared
void.
So IMHO those explicit gcc_unreachable () serve no purpose,
if they could be replaced by a comment. But since all cases
cover switches not handling a case or not returning will
likely cause some diagnostic to be emitted which is better
than running into an ICE only at runtime.
Bootstrapped and tested on x86_64-unknown-linux-gnu - any
comments?
Thanks,
Richard.
2021-11-24 Richard Biener <rguent...@suse.de>
* tree.h (reverse_storage_order_for_component_p): Remove
spurious gcc_unreachable.
* cfganal.c (dfs_find_deadend): Likewise.
* fold-const-call.c (fold_const_logb): Likewise.
(fold_const_significand): Likewise.
* gimple-ssa-store-merging.c (lhs_valid_for_store_merging_p):
Likewise.
gcc/c-family/
* c-format.c (check_format_string): Remove spurious
gcc_unreachable.
They would be a check if someone added a case to the switch that didn't
return. But we'd get a return-value warning if that happened. So I
don't see that they serve much purpose.
---
gcc/c-family/c-format.c | 2 --
gcc/cfganal.c | 2 --
gcc/fold-const-call.c | 2 --
gcc/gimple-ssa-store-merging.c | 2 --
gcc/tree.h | 2 --
5 files changed, 10 deletions(-)
diff --git a/gcc/c-family/c-format.c b/gcc/c-family/c-format.c
index e735e092043..617fb5ea626 100644
--- a/gcc/c-family/c-format.c
+++ b/gcc/c-family/c-format.c
@@ -296,8 +296,6 @@ check_format_string (const_tree fntype, unsigned
HOST_WIDE_INT format_num,
*no_add_attrs = true;
return false;
}
-
- gcc_unreachable ();
}
/* Under the control of FLAGS, verify EXPR is a valid constant that
diff --git a/gcc/cfganal.c b/gcc/cfganal.c
index 0cba612738d..48598e55c01 100644
--- a/gcc/cfganal.c
+++ b/gcc/cfganal.c
@@ -752,8 +752,6 @@ dfs_find_deadend (basic_block bb)
next = e ? e->dest : EDGE_SUCC (bb, 0)->dest;
}
}
-
- gcc_unreachable ();
}
diff --git a/gcc/fold-const-call.c b/gcc/fold-const-call.c
index d6cb9b11a31..c542e780a18 100644
--- a/gcc/fold-const-call.c
+++ b/gcc/fold-const-call.c
@@ -429,7 +429,6 @@ fold_const_logb (real_value *result, const real_value *arg,
}
return false;
}
- gcc_unreachable ();
}
/* Try to evaluate:
@@ -463,7 +462,6 @@ fold_const_significand (real_value *result, const
real_value *arg,
}
return false;
}
- gcc_unreachable ();
}
/* Try to evaluate:
diff --git a/gcc/gimple-ssa-store-merging.c b/gcc/gimple-ssa-store-merging.c
index e7c90ba8b59..13413ca4cd6 100644
--- a/gcc/gimple-ssa-store-merging.c
+++ b/gcc/gimple-ssa-store-merging.c
@@ -4861,8 +4861,6 @@ lhs_valid_for_store_merging_p (tree lhs)
default:
return false;
}
-
- gcc_unreachable ();
}
/* Return true if the tree RHS is a constant we want to consider
diff --git a/gcc/tree.h b/gcc/tree.h
index f0e72b55abe..094501bd9b1 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -5110,8 +5110,6 @@ reverse_storage_order_for_component_p (tree t)
default:
return false;
}
-
- gcc_unreachable ();
}
/* Return true if T is a storage order barrier, i.e. a VIEW_CONVERT_EXPR
