[gcc r11-8742] fix typo in attr_fnspec::verify

[gcc r11-8742] fix typo in attr_fnspec::verify

[Alexandre Oliva]

https://gcc.gnu.org/g:10a882eec2eca8fe5a1778112bdd8ed30c2df3c5

commit r11-8742-g10a882eec2eca8fe5a1778112bdd8ed30c2df3c5
Author: Alexandre Oliva <oliva@adacore.com>
Date:   Wed Jul 14 13:03:23 2021 -0300

    fix typo in attr_fnspec::verify
    
    Odd-numbered indices describing argument access sizes in the fnspec
    string can only hold 't' or a digit, as tested in the beginning of the
    case.  When checking that the size-supplying argument does not have
    additional information associated with it, the test that excludes the
    't' possibility looks for it at the even position in the fnspec
    string.  Oops.
    
    This might yield false positives and negatives if a function has a
    fnspec in which an argument uses a 't' access-size, and ('t' - '1')
    happens to be the index of an argument described in an fnspec string.
    Assuming ASCII encoding, it would take a function with at least 68
    arguments described in fnspec.  Still, probably worth fixing.
    
    
    for  gcc/ChangeLog
    
            * tree-ssa-alias.c (attr_fnspec::verify): Fix index in
            non-'t'-sized arg check.
    
    (cherry picked from commit a7098d6ef4e4e799dab8ef925c62b199d707694b)

Diff:
---
 gcc/tree-ssa-alias.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gcc/tree-ssa-alias.c b/gcc/tree-ssa-alias.c
index ebb3f49c86c..3e578e5d05f 100644
--- a/gcc/tree-ssa-alias.c
+++ b/gcc/tree-ssa-alias.c
@@ -3868,7 +3868,7 @@ attr_fnspec::verify ()
 		    && str[idx] != 'w' && str[idx] != 'W'
 		    && str[idx] != 'o' && str[idx] != 'O')
 		  err = true;
-		if (str[idx] != 't'
+		if (str[idx + 1] != 't'
 		    /* Size specified is scalar, so it should be described
 		       by ". " if specified at all.  */
 		    && (arg_specified_p (str[idx + 1] - '1')