[cfe-commits] Alignment of return from __builtin_alloca

[Chandler Carruth]

This seems generally fine to me, although I'd like John or someone to
confirm it's the right behavior on Darwin.

Also, you need test cases. =]

On Thu, Jun 7, 2012 at 2:23 PM, David Sehr <sehr at google.com> wrote:

> All,
>
> I have recently been debugging a failure with one of the tests from
> the gcc torture test suite and discovered that gcc and llvm seem to
> differ on whether __builtin_alloca is aligned more than 0mod4 (gcc
> thinks it's aligned by what clang stores inTargetInfo::SuitableAlign).
>  Below is a patch that (1) changes the alignment of __builtin_alloca
> for all targets, (2) adds setting SuitableAlign to the PNaCl target,
> and (3) fixes the size and alignment of v128 for PNaCl.  Please let me
> know how to proceed.
>
> David
>
> ----
> Index: lib/Basic/Targets.cpp
> ===================================================================
> --- lib/Basic/Targets.cpp (revision 158168)
> +++ lib/Basic/Targets.cpp (working copy)
> @@ -3888,6 +3888,7 @@
>     this->LongWidth = 32;
>     this->PointerAlign = 32;
>     this->PointerWidth = 32;
> +    this->SuitableAlign = 128;
>     this->IntMaxType = TargetInfo::SignedLongLong;
>     this->UIntMaxType = TargetInfo::UnsignedLongLong;
>     this->Int64Type = TargetInfo::SignedLongLong;
> @@ -3899,7 +3900,7 @@
>     this->IntPtrType = TargetInfo::SignedInt;
>     this->RegParmMax = 2;
>     DescriptionString = "e-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-"
> -                        "f32:32:32-f64:64:64-p:32:32:32-v128:32:32";
> +                        "f32:32:32-f64:64:64-p:32:32:32-v128:128:128";
>   }
>
>   void getDefaultFeatures(llvm::StringMap<bool> &Features) const {
> Index: lib/CodeGen/CGBuiltin.cpp
> ===================================================================
> --- lib/CodeGen/CGBuiltin.cpp (revision 158168)
> +++ lib/CodeGen/CGBuiltin.cpp (working copy)
> @@ -536,7 +536,9 @@
>   case Builtin::BIalloca:
>   case Builtin::BI__builtin_alloca: {
>     Value *Size = EmitScalarExpr(E->getArg(0));
> -    return RValue::get(Builder.CreateAlloca(Builder.getInt8Ty(), Size));
> +    AllocaInst *Alloca = Builder.CreateAlloca(Builder.getInt8Ty(), Size);
> +    Alloca->setAlignment(CGM.getTarget().getSuitableAlign() / 8);
> +    return RValue::get(Alloca);
>   }
>   case Builtin::BIbzero:
>   case Builtin::BI__builtin_bzero: {
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