[LLVMdev] ptrtoint

[Jingyue Wu]

Hi Reed,

I think you can try this:
1. write C/C++ code that use ptrtoint_i1 (declare ptrtoint_i1 as an
external function)
2. compile it using clang to LLVM IR,
3. link the compiled IR with the IR for ptrtoint_i1 to executable using
llvm-ld or the clang driver.

However, one complication in your case is I doubt there's a mapping from
any C/C++ type to i1 (bool is translated to i8). If that's the case, you
may need to put a wrapper around ptrtoint_i1, e.g.,
define void @ptrtoint_i8(i8* a, i8* b) {
  %slot = alloca i1
  call void @ptrtoint_i1(i8* a, i1* %slot)
  %value = load i1* %slot
  %ext_value = zext i1 %value to i8
  store i8 %ext_value, i8* b
}
// not tested :) be careful when you copy and paste
Then, you can use ptrtoint_i8(char *, char *) in your C/C++ code, and when
linked ptrtoint_i1 will show up too.

Jingyue

On Tue Sep 30 2014 at 3:35:14 PM Reed Kotler <rkotler at mips.com> wrote:

> If you can't make an executable test from C or C++ code then how do you
> know something works.
>
> Just by examination of the .s?
>
>
> On 09/30/2014 03:18 PM, Reed Kotler wrote:
> > If I wanted to call this function that they generated by hand, from C or
> > C+ code, how would that be done?
> >
> > if have seen cases where a real boolean gets generated but it was
> > something fairly involved.
> >
> > is a boolean and a char supposed to occupy the same amount of storage?
> >
> > is this prototype going to work in general:
> >
> > void ptrtoint_i1(char *p, bool *q)
> >
> > TIA.
> >
> > Reed
> >
> > On 09/29/2014 03:15 PM, reed kotler wrote:
> >> Technically I don't need C/C++ code for it.
> >>
> >> I'm not really very good at writing LLVM assembly code by hand
> >> (but I should be - lol ).
> >>
> >> I'm working on fast-isel and I want to have executable tests for all of
> >> this
> >> and not just make check tests.
> >>
> >> It's easier for me to do that in C/C++ and then save the .ll and morph
> >> it into
> >> a make check test.
> >>
> >> I'm going through the fast-isel tests for x86 now and adapting them for
> >> Mips.
> >> (will do the same for AArch64 and other ports).
> >>
> >> I want an executable variant for all of them.
> >>
> >> On 09/29/2014 03:11 PM, Duncan P. N. Exon Smith wrote:
> >>>> On Sep 29, 2014, at 2:29 PM, reed kotler <rkotler at mips.com> wrote:
> >>>>
> >>>> Thanks.
> >>>>
> >>>> So what about a fragment like this: (taken from fast-isel.ll in X86 )
> >>>>
> >>>> define void @ptrtoint_i1(i8* %p, i1* %q) nounwind {
> >>>>   %t = ptrtoint i8* %p to i1
> >>>>   store i1 %t, i1* %q
> >>>>   ret void
> >>>> }
> >>> Intuitively, this looks like:
> >>>
> >>>      void ptrtoint_i1(char *p, bool *q) { *q = (bool)p; }
> >>>
> >>> However, `q` needs to be addressable in C/C++, so it's left as an `i8`.
> >>>
> >>> `git log` suggests this particular testcase evolved incrementally out
> >>> of hand-written IR.
> >>>
> >>> Why do you need C/C++ code for it?  Just interested?
> >>>
> >>>> TIA.
> >>>>
> >>>> On 09/29/2014 02:16 PM, Duncan P. N. Exon Smith wrote:
> >>>>>> On Sep 29, 2014, at 1:51 PM, reed kotler <rkotler at mips.com> wrote:
> >>>>>>
> >>>>>> What kind of C or C++ code will emit a "ptrtoint" op?
> >>>>> This C code:
> >>>>>
> >>>>>      long ptrtoint(void *p) { return (long)p; }
> >>>>>
> >>>>> gives:
> >>>>>
> >>>>>      define i64 @ptrtoint(i8* %p) {
> >>>>>        %1 = ptrtoint i8* %p to i64
> >>>>>        ret i64 %1
> >>>>>      }
> >>>>>
> >>>>>
> >>>>>> Also, what causes i1 to be emitted?
> >>>>> This C++ code:
> >>>>>
> >>>>>      bool i1() { return false; }
> >>>>>
> >>>>> gives:
> >>>>>
> >>>>>      define zeroext i1 @_Z2i1v() {
> >>>>>        ret i1 false
> >>>>>      }
> >>>>>
> >>>>>
> >>>>>> Tia.
> >>>>>>
> >>>>>> Reed
> >>>>>> _______________________________________________
> >>>>>> LLVM Developers mailing list
> >>>>>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> >>>>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
> _______________________________________________
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