[llvm-commits] [llvm] r142992 - in /llvm/trunk: lib/VMCore/Instructions.cpp test/Bitcode/shuffle.ll

[Duncan Sands]

Hi,

> The bitcode reader can create an shuffle with a place holder mask which it will
> fix up later. For this special case, allow such a mask to be considered valid.
> <rdar://problem/8622574>

why does it create a placeholder - is it really needed?  I mean, I don't see any
other special casing of UserOp in Instructions.cpp, so it seems that no other
instructions do this - in which case what makes shufflevector different?  Also,
if you do follow this route, maybe you can have the verifier check that the
mask is really valid (no UserOp1).  This would catch bugs in which the
placeholder leaked out of the bitcode reader somehow.

Ciao, Duncan.

>
> Added:
>      llvm/trunk/test/Bitcode/shuffle.ll
> Modified:
>      llvm/trunk/lib/VMCore/Instructions.cpp
>
> Modified: llvm/trunk/lib/VMCore/Instructions.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/VMCore/Instructions.cpp?rev=142992&r1=142991&r2=142992&view=diff
> ==============================================================================
> --- llvm/trunk/lib/VMCore/Instructions.cpp (original)
> +++ llvm/trunk/lib/VMCore/Instructions.cpp Tue Oct 25 19:34:48 2011
> @@ -1576,10 +1576,17 @@
>           return false;
>         }
>       }
> -  }
> -  else if (!isa<UndefValue>(Mask)&&  !isa<ConstantAggregateZero>(Mask))
> +  } else if (!isa<UndefValue>(Mask)&&  !isa<ConstantAggregateZero>(Mask)) {
> +    // The bitcode reader can create a place holder for a forward reference
> +    // used as the shuffle mask. When this occurs, the shuffle mask will
> +    // fall into this case and fail. To avoid this error, do this bit of
> +    // ugliness to allow such a mask pass.
> +    if (const ConstantExpr* CE = dyn_cast<ConstantExpr>(Mask)) {
> +      if (CE->getOpcode() == Instruction::UserOp1)
> +        return true;
> +    }
>       return false;
> -
> +  }
>     return true;
>   }
>
>
> Added: llvm/trunk/test/Bitcode/shuffle.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Bitcode/shuffle.ll?rev=142992&view=auto
> ==============================================================================
> --- llvm/trunk/test/Bitcode/shuffle.ll (added)
> +++ llvm/trunk/test/Bitcode/shuffle.ll Tue Oct 25 19:34:48 2011
> @@ -0,0 +1,31 @@
> +; RUN: llvm-as<  %s | llvm-dis
> +
> +;<rdar://problem/8622574>
> +; tests the bitcodereader can handle the case where the reader will initially
> +; create shuffle with a place holder mask.
> +
> +
> +define<4 x float>  @test(<2 x double>  %d2)  {
> +entry:
> +  %call20.i = tail call<4 x float>  @cmp(<2 x double>  %d2,
> +<2 x double>  bitcast (
> +<4 x float>  shufflevector (
> +<3 x float>  shufflevector (
> +<4 x float>  shufflevector (
> +<3 x float>  bitcast (
> +                                                  i96 trunc (
> +                                                    i128 bitcast (<2 x double>  bitcast (
> +<4 x i32>  <i32 0, i32 0, i32 0, i32 undef>  to<2 x double>)
> +                                                    to i128) to i96)
> +                                                  to<3 x float>),
> +<3 x float>  undef,
> +<4 x i32>  <i32 0, i32 1, i32 2, i32 undef>),
> +<4 x float>  undef,
> +<3 x i32>  <i32 0, i32 1, i32 2>),
> +<3 x float>  undef,
> +<4 x i32>  <i32 0, i32 1, i32 2, i32 undef>)
> +                                          to<2 x double>))
> +  ret<4 x float>  %call20.i
> +}
> +
> +declare<4 x float>  @cmp(<2 x double>,<2 x double>)
>
>
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