| Message ID | 8de8f5f3-08b9-0c4f-a391-7ac752b1aac8@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | update get_range_strlen description | expand |
On Thu, Jun 06, 2019 at 01:32:14PM -0600, Martin Sebor wrote: > Hi Jeff, > > It looks like the updated comment for get_range_strlen didn't make > it into the strlen fixup commits last December and the function > still has the old description. (Not surprising given there are > at least two overloads of the same function and things moving > between them.) I'm going to check in the comment from the patch > here: https://gcc.gnu.org/ml/gcc-patches/2018-11/msg02050.html > with an additional sentence describing ELTSIZE. > > Let me know if you'd like me to tweak it or if spot something > else. > > Thanks > Martin > gcc/ChangeLog: > > * gimple-fold.c (get_range_strlen): Update comment that didn't > make it into r267503 or related commits. > > diff --git a/gcc/gimple-fold.c b/gcc/gimple-fold.c > index b3e931744f8..18860bb7c28 100644 > --- a/gcc/gimple-fold.c > +++ b/gcc/gimple-fold.c > @@ -1672,30 +1672,16 @@ get_range_strlen (tree arg, bitmap *visited, > } > } > > -/* Determine the minimum and maximum value or string length that ARG > - refers to and store each in the first two elements of MINMAXLEN. > - For expressions that point to strings of unknown lengths that are > - character arrays, use the upper bound of the array as the maximum > - length. For example, given an expression like 'x ? array : "xyz"' > - and array declared as 'char array[8]', MINMAXLEN[0] will be set > - to 0 and MINMAXLEN[1] to 7, the longest string that could be > - stored in array. > - Return true if the range of the string lengths has been obtained > - from the upper bound of an array at the end of a struct. Such > - an array may hold a string that's longer than its upper bound > - due to it being used as a poor-man's flexible array member. > - > - STRICT is true if it will handle PHIs and COND_EXPRs conservatively > - and false if PHIs and COND_EXPRs are to be handled optimistically, > - if we can determine string length minimum and maximum; it will use > - the minimum from the ones where it can be determined. > - STRICT false should be only used for warning code. > - When non-null, clear *NONSTR if ARG refers to a constant array > - that is known not be nul-terminated. Otherwise set it to > - the declaration of the constant non-terminated array. > - > - ELTSIZE is 1 for normal single byte character strings, and 2 or > - 4 for wide characer strings. ELTSIZE is by default 1. */ > +/* Try to obtain the range of the lengths of the string(s) referenced > + by ARG, or the size of the largest array ARG refers to if the range > + of lengths cannot be determined, and store all in *PDATA. ELTSIZE > + is the expected size of the string element in bytes: 1 for char and > + some power of 2 for wide characters. > + Return true if the range [PDATA->MINLEN, PDATA->MAXLEN] is suitable > + for optimization. Returning false means that a nonzero PDATA->MINLEN > + doesn't reflect the true lower bound of the range when PDATA->MAXLEN ^^ There are two spaces instead of one. No need to repost just because of this, of course. Marek
On 6/6/19 1:32 PM, Martin Sebor wrote: > Hi Jeff, > > It looks like the updated comment for get_range_strlen didn't make > it into the strlen fixup commits last December and the function > still has the old description. (Not surprising given there are > at least two overloads of the same function and things moving > between them.) I'm going to check in the comment from the patch > here: https://gcc.gnu.org/ml/gcc-patches/2018-11/msg02050.html > with an additional sentence describing ELTSIZE. > > Let me know if you'd like me to tweak it or if spot something > else. > > Thanks > Martin > > gcc-gimple-fold-get_range_strlen-comment.diff > > gcc/ChangeLog: > > * gimple-fold.c (get_range_strlen): Update comment that didn't > make it into r267503 or related commits. OK. Sorry about that. Not sure how I missed it. It's all a bit of a blur at this point. jeff
gcc/ChangeLog: * gimple-fold.c (get_range_strlen): Update comment that didn't make it into r267503 or related commits. diff --git a/gcc/gimple-fold.c b/gcc/gimple-fold.c index b3e931744f8..18860bb7c28 100644 --- a/gcc/gimple-fold.c +++ b/gcc/gimple-fold.c @@ -1672,30 +1672,16 @@ get_range_strlen (tree arg, bitmap *visited, } } -/* Determine the minimum and maximum value or string length that ARG - refers to and store each in the first two elements of MINMAXLEN. - For expressions that point to strings of unknown lengths that are - character arrays, use the upper bound of the array as the maximum - length. For example, given an expression like 'x ? array : "xyz"' - and array declared as 'char array[8]', MINMAXLEN[0] will be set - to 0 and MINMAXLEN[1] to 7, the longest string that could be - stored in array. - Return true if the range of the string lengths has been obtained - from the upper bound of an array at the end of a struct. Such - an array may hold a string that's longer than its upper bound - due to it being used as a poor-man's flexible array member. - - STRICT is true if it will handle PHIs and COND_EXPRs conservatively - and false if PHIs and COND_EXPRs are to be handled optimistically, - if we can determine string length minimum and maximum; it will use - the minimum from the ones where it can be determined. - STRICT false should be only used for warning code. - When non-null, clear *NONSTR if ARG refers to a constant array - that is known not be nul-terminated. Otherwise set it to - the declaration of the constant non-terminated array. - - ELTSIZE is 1 for normal single byte character strings, and 2 or - 4 for wide characer strings. ELTSIZE is by default 1. */ +/* Try to obtain the range of the lengths of the string(s) referenced + by ARG, or the size of the largest array ARG refers to if the range + of lengths cannot be determined, and store all in *PDATA. ELTSIZE + is the expected size of the string element in bytes: 1 for char and + some power of 2 for wide characters. + Return true if the range [PDATA->MINLEN, PDATA->MAXLEN] is suitable + for optimization. Returning false means that a nonzero PDATA->MINLEN + doesn't reflect the true lower bound of the range when PDATA->MAXLEN + is -1 (in that case, the actual range is indeterminate, i.e., + [0, PTRDIFF_MAX - 2]. */ bool get_range_strlen (tree arg, c_strlen_data *pdata, unsigned eltsize)