Re: [patch] Fix wrong code for return of small aggregates on big-endian

[Richard Biener <richard.guenther@gmail.com>]

On Mon, Jan 9, 2017 at 11:43 AM, Eric Botcazou <ebotcazou@adacore.com> wrote:
> Hi,
>
> this is a regression present on all active branches for big-endian targets
> returning small aggregate types in registers under certain circumstances and
> when optimization is enabled: when the bitfield path of store_field is taken,
> the function ends up calling store_bit_field to store the value.  Now the
> behavior of store_bit_field is awkward when the mode is BLKmode: it always
> takes its value from the lsb up to the word size but expects it left justified
> beyond it (see expmed.c:890 and below) and I missed that when I got rid of the
> stack temporaries that were originally generated in that case.
>
> Of course that's OK for little-endian targets but not for big-endian targets,
> and I have a couple of C++ testcases exposing the issue on SPARC 64-bit and a
> couple of Ada testcases exposing the issue on PowerPC with the SVR4 ABI (the
> Linux ABI is immune since it always returns on the stack); I think they cover
> all the cases in the problematic code.
>
> The attached fix was tested on a bunch of platforms: x86/Linux, x86-64/Linux,
> PowerPC/Linux, PowerPC64/Linux, PowerPC/VxWorks, Aarch64/Linux, SPARC/Solaris
> and SPARC64/Solaris with no regressions.  OK for the mainline? other branches?

Ok for trunk and branches after a short burn-in.

Thanks,
Richard.

>
> 2017-01-09  Eric Botcazou  <ebotcazou@adacore.com>
>
>         * expr.c (store_field): In the bitfield case, if the value comes from
>         a function call and is of an aggregate type returned in registers, do
>         not modify the field mode; extract the value in all cases if the mode
>         is BLKmode and the size is not larger than a word.
>
>
> 2017-01-09  Eric Botcazou  <ebotcazou@adacore.com>
>
>         * g++.dg/opt/call2.C: New test.
>         * g++.dg/opt/call3.C: Likewise.
>         * gnat.dg/array26.adb: New test.
>         * gnat.dg/array26_pkg.ad[sb]: New helper.
>         * gnat.dg/array27.adb: New test.
>         * gnat.dg/array27_pkg.ad[sb]: New helper.
>         * gnat.dg/array28.adb: New test.
>         * gnat.dg/array28_pkg.ad[sb]: New helper.
>
> --
> Eric Botcazou