On 6/24/19 5:59 PM, Jeff Law wrote:
On 6/24/19 5:50 PM, Martin Sebor wrote:
The strlen enhancement committed in r263018 to handle multi-character
assignments extended the handle_char_store() function to handle such
stores via MEM_REFs. Prior to that the function only dealt with
single-char stores. The enhancement neglected to constrain a case
in the function that assumed the function's previous constraint.
As a result, when the original optimization takes place with
a multi-character store, the function computes the wrong string
length.
The attached patch adds the missing constraint.
Martin
gcc-90989.diff
PR tree-optimization - incorrrect strlen result after second strcpy into
the same destination
gcc/ChangeLog:
* tree-ssa-strlen.c (handle_char_store): Constrain a single character
optimization to just single character stores.
gcc/testsuite/ChangeLog:
* gcc.dg/strlenopt-26.c: Exit with test result status.
* gcc.dg/strlenopt-67.c: New test.
Index: gcc/tree-ssa-strlen.c
===================================================================
--- gcc/tree-ssa-strlen.c (revision 272618)
+++ gcc/tree-ssa-strlen.c (working copy)
@@ -3462,34 +3462,38 @@ handle_char_store (gimple_stmt_iterator *gsi)
return false;
}
}
- /* If si->nonzero_chars > OFFSET, we aren't overwriting '\0',
- and if we aren't storing '\0', we know that the length of the
- string and any other zero terminated string in memory remains
- the same. In that case we move to the next gimple statement and
- return to signal the caller that it shouldn't invalidate anything.
- This is benefical for cases like:
+ if (cmp > 0
+ && storing_nonzero_p
+ && TREE_CODE (TREE_TYPE (rhs)) == INTEGER_TYPE)
I'm not sure I follow why checking for TREE_CODE (TREE_TYPE (rhs)) ==
INTEGER_TYPE helps here. If you need to check that we're storing bytes,
then don't you need to check the size, not just the TREE_CODE of the type?
handle_char_store is only called for single-character assignments
or MEM_REF assignments to/from arrays. The type of the RHS is only
integer when storing a single character.
To determine the number of characters, the subsequent handling in
the block below calls get_min_string_length which also relies on
INTEGRAL_TYPE_P to get the "length" of a single character (zero
or 1).
Martin
