]> git.ipfire.org Git - people/ms/gcc.git/commit
builtins: Move the character difference into result instead of reassigning result...
authorXi Ruoyao <xry111@xry111.site>
Wed, 15 Mar 2023 07:34:52 +0000 (15:34 +0800)
committerXi Ruoyao <xry111@xry111.site>
Wed, 15 Mar 2023 09:28:13 +0000 (17:28 +0800)
commit45641f3a99281bb0a429649741a29c2aace4c63e
tree15089cf7c6fcf11508ea436428b074301a1cf5a5
parent02fcaf412ae9508b75efa9602cd4ac58bc63d6a4
builtins: Move the character difference into result instead of reassigning result [PR109086]

expand_simple_binop() is allowed to allocate a new pseudo-register and
return it, instead of forcing the result into the provided
pseudo-register.  This can cause a problem when we expand the unrolled
loop for __builtin_strcmp: the compiler always generates code for all n
iterations of the loop, so "result" will be an alias of the
pseudo-register allocated and used in the last iteration; but at runtime
the loop can break early, causing this pseudo-register uninitialized.

Emit a move instruction in the iteration to force the difference into
one register which has been allocated before the loop, to avoid this
issue.

gcc/ChangeLog:

PR other/109086
* builtins.cc (inline_string_cmp): Force the character
difference into "result" pseudo-register, instead of reassign
the pseudo-register.
gcc/builtins.cc