[llvm-commits] [llvm-gcc-4.2] r108206 - /llvm-gcc-4.2/trunk/gcc/llvm-convert.cpp

[Jim Grosbach]

The diagnostic needs to be a bit broader than this, actually. It's not just the variable sized allocation that can't be dynamically aligned, but any declaration in the same function. That is, a function which has variable sized stack objects cannot also contain stack objects which require dynamic stack realignment.

-Jim

On Jul 12, 2010, at 4:02 PM, Eric Christopher wrote:

> Author: echristo
> Date: Mon Jul 12 18:02:56 2010
> New Revision: 108206
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=108206&view=rev
> Log:
> Make sure that the requested alignment isn't greater than the stack alignment
> for a vla - we won't adhere to it anyways so make it an error.
> 
> Fixes rdar://7506902
> 
> Modified:
>    llvm-gcc-4.2/trunk/gcc/llvm-convert.cpp
> 
> Modified: llvm-gcc-4.2/trunk/gcc/llvm-convert.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm-gcc-4.2/trunk/gcc/llvm-convert.cpp?rev=108206&r1=108205&r2=108206&view=diff
> ==============================================================================
> --- llvm-gcc-4.2/trunk/gcc/llvm-convert.cpp (original)
> +++ llvm-gcc-4.2/trunk/gcc/llvm-convert.cpp Mon Jul 12 18:02:56 2010
> @@ -39,6 +39,7 @@
> #include "llvm/Target/TargetLowering.h"
> #include "llvm/Target/TargetData.h"
> #include "llvm/Target/TargetMachine.h"
> +#include "llvm/Target/TargetFrameInfo.h"
> #include "llvm/ADT/StringExtras.h"
> #include "llvm/ADT/DenseMap.h"
> 
> @@ -1755,6 +1756,15 @@
>   if (isGimpleTemporary(decl))
>     return;
> 
> +  /* If this is a vla type and we requested an alignment greater than the stack
> +     alignment, error out since we're not going to dynamically realign
> +     variable length array allocations.  We're placing this here instead of
> +     later in case it's a relatively unused variable.  */
> +  if (TREE_CODE (type) == ARRAY_TYPE && C_TYPE_VARIABLE_SIZE (type) &&
> +      DECL_ALIGN(decl)/8u > TheTarget->getFrameInfo()->getStackAlignment())
> +        error ("alignment for %q+D is greater than the stack alignment, "
> +               "we cannot guarantee the alignment.", decl);
> +
>   // If this is just the rotten husk of a variable that the gimplifier
>   // eliminated all uses of, but is preserving for debug info, ignore it.
>   if (TREE_CODE(decl) == VAR_DECL && DECL_VALUE_EXPR(decl))
> 
> 
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