[LLVMdev] ptrtoint

[reed kotler]

I understand what you are suggesting and thought of this myself but it 
really
does not help unless we say that

size(i1) == size(i8)

which is certainly logical

i have seen i1 get generated with C/c++ code but am not sure
how to construct this case myself.

so some of the test cases, like fast-isel.ll for X86 are probably
only eyeballed to see of ptrtoint and inttoptr work

On 09/30/2014 03:47 PM, Jingyue Wu wrote:
> 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 
> <mailto: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
>     <mailto: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
>     <mailto: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
>     >>>>>> _______________________________________________
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