[gcc(refs/users/aoliva/heads/testme)] vartrack: fix skipping of unsuitable locs

[Alexandre Oliva]

https://gcc.gnu.org/g:2721a5834bb0b7d59e2fb9864448f148f87f5fff

commit 2721a5834bb0b7d59e2fb9864448f148f87f5fff
Author: Alexandre Oliva <oliva@adacore.com>
Date:   Wed Dec 17 02:44:31 2025 -0300

    vartrack: fix skipping of unsuitable locs
    
    When the last loc in a chain happens to be an unsuitable_loc(), we
    record VAR_LOC_FROM as if the empty location had been derived from
    that unsuitable loc, instead of leaving it empty, which ends up
    preventing the VAR loc from being recomputed when other related locs
    are usefully expanded.
    
    Adjust the code that skips an unsuitable_loc() to take the same
    preparation steps we take for exiting the loop as when an expansion
    attempt yields NULL_RTX.
    
    
    for  gcc/ChangeLog
    
            * var-tracking.cc (vt_expand_var_loc_chain): Prepare to exit
            the loop after unsuitable_loc.

Diff:
---
 gcc/var-tracking.cc | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/gcc/var-tracking.cc b/gcc/var-tracking.cc
index 8732c3ba62aa..7c255b1a8833 100644
--- a/gcc/var-tracking.cc
+++ b/gcc/var-tracking.cc
@@ -8397,7 +8397,7 @@ vt_expand_var_loc_chain (variable *var, bitmap regs, void *data,
 	  next = loc;
 	  cloc = cloc->next;
 	  if (unsuitable_loc (loc_from))
-	    continue;
+	    goto try_next_loc;
 	}
       else
 	{
@@ -8437,6 +8437,7 @@ vt_expand_var_loc_chain (variable *var, bitmap regs, void *data,
 	  result = NULL;
 	}
 
+    try_next_loc:
       /* Set it up in case we leave the loop.  */
       depth.complexity = depth.entryvals = 0;
       loc_from = NULL;