[llvm-commits] [PATCH] Fix for PR 14652 and 14740

[Akira Hatanaka]

I created a new patch which factors out the code in
SelectionDAGBuilder::visitShift and fixes the bug I mentioned in my
previous email.

Note that, in the patch, I also fixed two lines in
SelectionDAGBuilder::visitShift, which I think are bugs (please correct me
if I am wrong). I believe these bugs haven't caused any problems in
practice, but I think it is still important to fix them.

First, we should pass the type of LHS (the shiftee), not the type of the
RHS (shift amount), to getShiftAmountTy:

-  MVT ShiftTy = TLI.getShiftAmountTy(Op2.getValueType());

Second, we should compute the log of the size of the LHS (the shiftee) when
we decide whether ShiftSize is large enough:

-    else if (ShiftSize >= Log2_32_Ceil(Op2.getValueType().getSizeInBits()))


On Thu, Jan 17, 2013 at 2:38 PM, Eli Friedman <eli.friedman at gmail.com>wrote:

> On Tue, Jan 15, 2013 at 2:51 PM, Akira Hatanaka <ahatanak at gmail.com>
> wrote:
> >
> > The attached patch is an attempt to fix the following bugs:
> >
> > http://llvm.org/bugs/show_bug.cgi?id=14652
> > http://llvm.org/bugs/show_bug.cgi?id=14740
> >
> > It fixes the code which scalarizes vector shifts and ensures that the
> type
> > of the shift amount operand is the type TargetLowering::getShiftAmountTy
> > returns. This is the same approach taken in
> SelectionDAGBuilder::visitShift.
> >
> > The command that was failing in 14652 passes after this patch is applied
> > and fixes 14740 as well.
>
> The approach seems fine.  Can you factor out the logic into a utility
> function?
>
> -Eli
>
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