diff --git a/gcc/testsuite/g++.dg/diagnostic/pr77949.C b/gcc/testsuite/g++.dg/diagnostic/pr77949.C
index b81d6e2bb46..35922e9bb23 100644
--- a/gcc/testsuite/g++.dg/diagnostic/pr77949.C
+++ b/gcc/testsuite/g++.dg/diagnostic/pr77949.C
@@ -1,7 +1,10 @@
-// Ensure that no fix-it hints are emitted
+// Ensure that no fix-it hints are emitted unless large locations are available.
 // { dg-options "-fdiagnostics-parseable-fixits" }
 
 /* Very long line, where a missing semicolon would be suggested for
    insertion at column 4097.  */
 class test {                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   }   
 // { dg-error "-: expected .;. after class definition" "" { target *-*-* } .-1 }
+/* { dg-begin-multiline-output "" }
+fix-it:
+{ dg-end-multiline-output "" { target large_location_t } }  */
diff --git a/gcc/testsuite/g++.dg/modules/loc-prune-4.C b/gcc/testsuite/g++.dg/modules/loc-prune-4.C
index aa8f248b52b..a6c62a3385c 100644
--- a/gcc/testsuite/g++.dg/modules/loc-prune-4.C
+++ b/gcc/testsuite/g++.dg/modules/loc-prune-4.C
@@ -16,7 +16,12 @@ int bar (int); // merge lines
 int baz (int);
 
 
-// { dg-final { scan-lang-dump {Ordinary maps:2 locs:12288 range_bits:5} module } }
 // { dg-final { scan-lang-dump { 1 source file names\n Source file...=[^\n]*loc-prune-4.C\n} module } }
-// { dg-final { scan-lang-dump { Span:0 ordinary \[[0-9]+\+12288,\+4096\)->\[0,\+4096\)} module } }
-// { dg-final { scan-lang-dump { Span:1 ordinary \[[0-9]+\+40960,\+8192\)->\[4096,\+8192\)} module } }
+
+// { dg-final { scan-lang-dump {Ordinary maps:2 locs:12288 range_bits:5} module { target { ! large_location_t } } } }
+// { dg-final { scan-lang-dump { Span:0 ordinary \[[0-9]+\+12288,\+4096\)->\[0,\+4096\)} module { target { ! large_location_t } } } }
+// { dg-final { scan-lang-dump { Span:1 ordinary \[[0-9]+\+40960,\+8192\)->\[4096,\+8192\)} module { target { ! large_location_t } } } }
+
+// { dg-final { scan-lang-dump {Ordinary maps:2 locs:49152 range_bits:7} module { target large_location_t } } }
+// { dg-final { scan-lang-dump { Span:0 ordinary \[[0-9]+\+49152,\+16384\)->\[0,\+16384\)} module { target large_location_t } } }
+// { dg-final { scan-lang-dump { Span:1 ordinary \[[0-9]+\+163840,\+32768\)->\[16384,\+32768\)} module { target large_location_t } } }
diff --git a/gcc/testsuite/gcc.dg/plugin/expensive_selftests_plugin.c b/gcc/testsuite/gcc.dg/plugin/expensive_selftests_plugin.c
index e96efe0bed5..1b487ad63b6 100644
--- a/gcc/testsuite/gcc.dg/plugin/expensive_selftests_plugin.c
+++ b/gcc/testsuite/gcc.dg/plugin/expensive_selftests_plugin.c
@@ -63,17 +63,20 @@ test_richloc (rich_location *richloc)
 static void
 test_fixit_on_very_long_line (const line_table_case &case_)
 {
-  /* Various interesting column/line-width values, to try to tickle
-     out bugs.  */
+  /* Various interesting column/line-width values, to try to tickle out bugs. In
+     64-bit location mode, we can't test the max because the maximum supported
+     column is unreasonably large.  */
   const int VERY_LONG_LINE = 8192;
   const int columns[] = {0,
 			 1,
 			 80,
+#ifndef ENABLE_LARGE_SOURCE_LOCATIONS
 			 LINE_MAP_MAX_COLUMN_NUMBER - 2,
 			 LINE_MAP_MAX_COLUMN_NUMBER - 1,
 			 LINE_MAP_MAX_COLUMN_NUMBER,
 			 LINE_MAP_MAX_COLUMN_NUMBER + 1,
 			 LINE_MAP_MAX_COLUMN_NUMBER + 2,
+#endif
 			 VERY_LONG_LINE,
 			 VERY_LONG_LINE + 5};
   for (unsigned int width_idx = 0; width_idx < ARRAY_SIZE (columns);
diff --git a/gcc/testsuite/gcc.dg/plugin/location_overflow_plugin.c b/gcc/testsuite/gcc.dg/plugin/location_overflow_plugin.c
index 45a01b5f917..f7d7ca4b57c 100644
--- a/gcc/testsuite/gcc.dg/plugin/location_overflow_plugin.c
+++ b/gcc/testsuite/gcc.dg/plugin/location_overflow_plugin.c
@@ -84,6 +84,13 @@ plugin_init (struct plugin_name_args *plugin_info,
   if (!base_location)
     error_at (UNKNOWN_LOCATION, "missing plugin argument");
 
+  /* With 64-bit sources, the thresholds are larger, so shift the base
+     location argument accordingly.  */
+#ifdef ENABLE_LARGE_SOURCE_LOCATIONS
+  gcc_assert (sizeof (location_t) == sizeof (uint64_t));
+  base_location = 1 + ((base_location - 1) << 31);
+#endif
+
   register_callback (plugin_info->base_name,
 		     PLUGIN_PRAGMAS,
 		     on_pragma_registration,
diff --git a/gcc/testsuite/lib/target-supports.exp b/gcc/testsuite/lib/target-supports.exp
index 75703ddca60..f92dda583b1 100644
--- a/gcc/testsuite/lib/target-supports.exp
+++ b/gcc/testsuite/lib/target-supports.exp
@@ -180,13 +180,27 @@ proc clear_effective_target_cache { } {
     array unset et_cache
 }
 
-# Like check_compile, but delete the output file and return true if the
-# compiler printed no messages.
-proc check_no_compiler_messages_nocache {args} {
+# Like check_compile, but delete the output file and return just the
+# compiler output as a string.
+proc get_compiler_messages_nocache {args} {
     set result [eval check_compile $args]
     set lines [lindex $result 0]
     set output [lindex $result 1]
     remote_file build delete $output
+    return $lines
+}
+
+# And the cached version.
+proc get_compiler_messages {prop args} {
+    return [check_cached_effective_target $prop {
+	eval [list get_compiler_messages_nocache $prop] $args
+    }]
+}
+
+# Like check_compile, but delete the output file and return true if the
+# compiler printed no messages.
+proc check_no_compiler_messages_nocache {args} {
+    set lines [eval get_compiler_messages_nocache $args ]
     return [string match "" $lines]
 }
 
@@ -13939,3 +13953,17 @@ proc add_options_for_nvptx_alias_ptx { flags } {
 
     return $flags
 }
+
+
+# Return 1 if GCC was configured with large (64-bit) location_t.
+
+proc check_effective_target_large_location_t { } {
+    set lines [get_compiler_messages large_location_t assembly ";" "-fdump-internal-locations" ]
+    if ![ regexp {\nMAX_LOCATION_T\s*location_t interval: (\d*)} $lines dummy max_loc ] {
+	verbose "Could not parse output of -fdump-internal-locations. Assuming small location_t." 2
+	return 0
+    }
+    # No need to rely on 64-bit capable TCL here. The max for 32-bit locations
+    # is 2147483647, which is 10 characters long.
+    return [ expr { [string length $max_loc] > 10 } ]
+}
