[LLVMdev] Vector argument passing abi for ARM ?

[Sebastien DELDON-GNB]

Hi Rotem,

Thanks for the quick answer, how do I know which type is legal/illegal with respect to calling convention ?

Best Regards
Seb

> -----Original Message-----
> From: Rotem, Nadav [mailto:nadav.rotem at intel.com]
> Sent: Thursday, July 05, 2012 11:21 AM
> To: Sebastien DELDON-GNB; llvmdev at cs.uiuc.edu
> Subject: RE: Vector argument passing abi for ARM ?
> 
> The argument passing calling convention is undefined for illegal types,
> such as <2 x i8>. The invalid misaligned loads on ARM sounds like a bug
> in the ARM backend.
> 
> -----Original Message-----
> From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu]
> On Behalf Of Sebastien DELDON-GNB
> Sent: Thursday, July 05, 2012 12:14
> To: llvmdev at cs.uiuc.edu
> Subject: [LLVMdev] Vector argument passing abi for ARM ?
> 
> Hi all,
> 
> I was wondering if there is a defined ABI for passing vector as
> parameter for ARM target.
> For instance is this valid to write .ll statement like:
> 
> ; ModuleID = 'bugconv.ll'
> target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-
> i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-n32"
> target triple = "thumbv7-none-linux-androideabi"
> 
> define arm_aapcscc void @bugtest_CALL(i8* nocapture %.T_0375) nounwind
> {
> L.entry:
>   %0 = bitcast i8* %.T_0375 to <2 x i8>*
>   %1 = load <2 x i8>* %0, align 2
>   %2 = getelementptr i8* %.T_0375, i32 2
>   %3 = bitcast i8* %2 to <2 x i8>*
>   %4 = load <2 x i8>* %3, align 2
>   tail call arm_aapcscc  void @bugtest(<2 x i8> %1, <2 x i8> %4)
>   ret void
> }
> 
> declare arm_aapcscc void @bugtest(<2 x i8> %c, <2 x i8> %uc)
> 
> and expect first parameter to be passed into a single 32-bit register.
> using llc -mcpu=cortex-a9 -mattr=+neon
> With LLVM 3.0 %c is passed into two 32-bit regs and code works.
> With LLVM 3.1 it generate a misaligned load that cause a BUS error
> seems linked to promote element optimization.
> With LLVM trunk it generates a misaligned load that makes the assembler
> fail.
> I guess that to avoid such problem I need to convert small vector
> parameters into i32, right ?
> 
> Thanks for your answers
> Best Regards
> Seb
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