[PATCH] R600: Fix up for AsmPrinter's OutStreamer being a unique_ptr

[David Blaikie]

On Tue, Apr 28, 2015 at 6:53 AM, Tom Stellard <tom at stellard.net> wrote:
> On Mon, Apr 27, 2015 at 09:34:53AM -0700, David Blaikie wrote:
>> On Mon, Apr 27, 2015 at 2:59 AM, Michel Dänzer <michel at daenzer.net> wrote:
>> > From: Michel Dänzer <michel.daenzer at amd.com>
>> >
>> > Fixes a crash with basically any OpenGL application using the radeonsi
>> > driver.
>> >
>> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=90176
>> > Signed-off-by: Michel Dänzer <michel.daenzer at amd.com>
>> > ---
>> >  lib/Target/R600/AMDGPUMCInstLower.cpp | 4 ++--
>> >  1 file changed, 2 insertions(+), 2 deletions(-)
>> >
>> > diff --git a/lib/Target/R600/AMDGPUMCInstLower.cpp b/lib/Target/R600/AMDGPUMCInstLower.cpp
>> > index b00bd8d..708bb6f 100644
>> > --- a/lib/Target/R600/AMDGPUMCInstLower.cpp
>> > +++ b/lib/Target/R600/AMDGPUMCInstLower.cpp
>> > @@ -132,8 +132,8 @@ void AMDGPUAsmPrinter::EmitInstruction(const MachineInstr *MI) {
>> >        SmallVector<char, 16> CodeBytes;
>> >        raw_svector_ostream CodeStream(CodeBytes);
>> >
>> > -      MCObjectStreamer &ObjStreamer = (MCObjectStreamer &)OutStreamer;
>>
>> Well that's lovely... - anyone have interest in banning c-style casts
>> or a Clang warning for essentially reinterpret casts with c-style
>> casts? (similar to -Wcast-qual - essentially trying to push for
>> c-style casts to only be used for static_cast equivalent operations)
>>
>
> These kinds of casts are used a lot in the target AsmParsers too.  What
> kind of cast is correct here?

static_cast would've done the right thing and avoided the chance of
doing a bit-cast by accident (either at the original time it was
written, or later on)

The original code boiled down to something like this:

MCFooStreamer &Original = ...
MCStreamer &MCS = Original;
MCFooStreamer &ExtractTheOriginalAgain =
static_cast<MCFooStreamer&>(MCS); // this was where the unnecessarily
powerful c-style cast was used

>
> -Tom
>
>> > -      MCCodeEmitter &InstEmitter = ObjStreamer.getAssembler().getEmitter();
>> > +      MCObjectStreamer *ObjStreamer = (MCObjectStreamer *)OutStreamer.get();
>> > +      MCCodeEmitter &InstEmitter = ObjStreamer->getAssembler().getEmitter();
>> >        InstEmitter.EncodeInstruction(TmpInst, CodeStream, Fixups,
>> >                                      MF->getSubtarget<MCSubtargetInfo>());
>> >        CodeStream.flush();
>> > --
>> > 2.1.4
>> >
>> >
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