Hi!
I'd like to ping this patch. I know it isn't a full week yet, but we are
almost out of P1s and GCC 12 branching is any time now.
Thanks:
On Fri, Apr 22, 2022 at 09:25:04AM +0200, Jakub Jelinek via Gcc-patches wrote:
> On the following testcase we emit a bogus
> 'va_arg_tmp.5' may be used uninitialized
> warning. The reason is that when gimplifying the addr = &temp;
> statement, the va_arg_tmp temporary var for which we emit ADDR_EXPR
> is not TREE_ADDRESSABLE, prepare_gimple_addressable emits some extra
> code to initialize the newly addressable var from its previous value,
> but it is a new variable which hasn't been initialized yet and will
> be later, so we end up initializing it with uninitialized SSA_NAME:
> va_arg_tmp.6 = va_arg_tmp.5_14(D);
> addr.2_16 = &va_arg_tmp.6;
> _17 = MEM[(double *)sse_addr.4_13];
> MEM[(double * {ref-all})addr.2_16] = _17;
> and with -O1 we actually don't DSE it before the warning is emitted.
> If we make the temp TREE_ADDRESSABLE before the gimplification, then
> this prepare_gimple_addressable path isn't taken and we effectively
> omit the first statement above and so the bogus warning is gone.
>
> I went through other backends and didn't find another instance of this
> problem.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> 2022-04-22 Jakub Jelinek <[email protected]>
>
> PR target/105331
> * config/i386/i386.cc (ix86_gimplify_va_arg): Mark va_arg_tmp
> temporary TREE_ADDRESSABLE before trying to gimplify ADDR_EXPR
> of it.
>
> * gcc.dg/pr105331.c: New test.
Jakub
