[gcc r12-5576] Remove unreachable gcc_unreachable () at the end of functions

[Richard Biener <rguenth@gcc.gnu.org>]

https://gcc.gnu.org/g:a3b31fe3692894e80de16b4059a89a309e409687

commit r12-5576-ga3b31fe3692894e80de16b4059a89a309e409687
Author: Richard Biener <rguenther@suse.de>
Date:   Wed Nov 24 15:57:03 2021 +0100

    Remove unreachable gcc_unreachable () at the end of functions
    
    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.
    
    2021-11-24  Richard Biener  <rguenther@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.

Diff:
---
 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 a00370e2a37..29d5c2449ab 100644
--- a/gcc/gimple-ssa-store-merging.c
+++ b/gcc/gimple-ssa-store-merging.c
@@ -4867,8 +4867,6 @@ 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