[PATCH] InlineFunction doesn't update InlineFunctionInfo with allocas created for byval arguments

[Manman Ren]

On Tue, Apr 8, 2014 at 3:18 PM, Julien Lerouge <jlerouge at apple.com> wrote:

> On Tue, Apr 08, 2014 at 02:26:52PM -0700, Julien Lerouge wrote:
> > On Tue, Apr 08, 2014 at 10:30:44AM -0700, Manman Ren wrote:
> > > On Fri, Apr 4, 2014 at 5:15 PM, Julien Lerouge <julien.lerouge at m4x.org
> >wrote:
> > >
> > > > When llvm::InlineFunction inlines a function that has byval
> arguments,
> > > > it creates allocas in the caller. Those allocas aren't inserted in
> the
> > > > InlineFunctionInfo data structure. So after inlining, if the client
> code
> > > > wants to know where are the allocas that were created, it will miss
> > > > those.
> > > >
> > > > Should InlineFunctionInfo contain these allocas, or is the omission
> > > > deliberate ?
> > > >
> > >
> > > Hi Julien,
> > >
> > > I don't think the omission is deliberate, but I may be wrong.
> > > Do you have a testing case?
> > >
> > > Thanks,
> > > Manman
> > >
> >
> > Yeah, sorry, I'll add one and resend the patch.
> >
> > Thanks,
> > Julien
> >
>
> Attached below. The test just inlines a function with byval and makes
> sure the lifetime marker gets created. Without the fix, no lifetime
> marker is created.
>

Hi Julien,

Thanks for the testing case. However I don't think it is the right fix.
llvm.lifetime intrinsics are optimization hints. With this patch, we get
define i32 @main(i32 %argc, i8** %argv) {
entry:
  %gFoo = alloca %struct.foo, align 8
  %tmp = bitcast %struct.foo* %gFoo to i8*
  %tmp1 = bitcast %struct.foo* @gFoo to i8*
  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %tmp, i8* %tmp1, i64 ptrtoint
(%struct.foo* getelementptr (%struct.foo* null, i32 1) to i64), i32 1, i1
false)
  %0 = bitcast %struct.foo* %gFoo to i8*
  call void @llvm.lifetime.start(i64 -1, i8* %0)
  %a1.i = getelementptr inbounds %struct.foo* %gFoo, i32 0, i32 1
  %arrayidx.i = getelementptr inbounds [16 x i32]* %a1.i, i32 0, i32 %argc
  %tmp2.i = load i32* %arrayidx.i, align 1
  %1 = bitcast %struct.foo* %gFoo to i8*
  call void @llvm.lifetime.end(i64 -1, i8* %1)
  ret i32 %tmp2.i
}

lifetime.start after memcpy seems to be wrong because %gFoo is already live
at memcpy.
Do you see a performance issue or you happen to notice this when browsing
the code?

Thanks,
Manman
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