[LLVMdev] Inline Assembly: Memory constraints with offsets

[Daniel Sanders]

> -----Original Message-----
> From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu]
> On Behalf Of Krzysztof Parzyszek
> Sent: 03 March 2015 14:35
> To: llvmdev at cs.uiuc.edu
> Subject: Re: [LLVMdev] Inline Assembly: Memory constraints with offsets
> 
> On 3/3/2015 6:01 AM, Daniel Sanders wrote:
> > Hi,
> >
> > I'm trying to implement the ZC inline assembly constraint for Mips. This
> > constraint is a memory constraint that expands to an address with an
> > offset (the range of the offset varies according to the subtarget), so
> > the inline assembly in:
> >
> >    int data[10];
> >
> >    void ZC(void) {
> >
> >      asm volatile ("foo %0 %1" : : "ZC"(data[1]), "ZC"(data[2]));
> >
> >    }
> >
> > Should expand to something like:
> >
> >    foo 4($2) 8($2)
> >
> > At the moment, the best I can get is something like:
> >
> >    foo 0($2) 0($3)
> >
> > with the offsets being added before the inline assembly.
> >
> > Does anyone have any suggestions as to how I can get the offset inside
> > the inline assembly?
> 
> How are you actually getting this to compile?  I just built clang and
> I'm getting an error:
> 
> clang-3.6 -target mips -S mipsa.c
> mipsa.c:4:33: error: invalid input constraint 'ZC' in asm
>    asm volatile ("foo %0 %1" : : "ZC"(data[1]), "ZC"(data[2]));
>                                  ^
> 1 error generated.
> 
> 
> It doesn't seem that the function "validateAsmConstraint" in
> tools/clang/lib/Basic/Targets.cpp handles "ZC" as a constraint.
> 
> -Krzysztof

Partial support for ZC is in my working copy at the moment. I've attached my WIP patches.
 
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