search for: sizei

I'm trying to work out the size of a struct so that I can pass this to the 'llvm.memcpy' intrinsic. It's easy to find out how I'm supposed to do this, as I keep seeing the following: %Size = getelementptr %T* null, int 1 %SizeI = cast %T* %Size to uint But I'm unsure how I actually do this in the C++ API. Is the 'null' here a llvm::ConstantPointerNull? Any help here would be much appreciated. Additionally, I was wondering whether I can use this method to find out the size of variable-length arrays, such as [...

...nt i32** %tmp1 to i32 ; <i32> [#uses=1] %x45 = ptrtoint [2 x i32*]* %x to i32 ; <i32> [#uses=1] %tmp6 = sub i32 %tmp23, %x45 ; <i32> [#uses=1] %size = getelementptr i32** null, i32 1 ; <i32**> [#uses=1] %sizeI = ptrtoint i32** %size to i32 ; <i32> [#uses=1] %tmp7 = ashr i32 %tmp6, %sizeI ; <i32> [#uses=1] ret i32 %tmp7 } There, pointer size independent. The problem you see is you are using a frontend targeting a specific platform, so pointersize is known...

The LLVA and LLVM papers motivate the GetElementPtr instruction by arguing that it abstracts implementation details, in particular pointer size, from the compiler. While it does this fine for pointer addresses, it does not manage it for address offsets. Consider the following code: $ cat test.c int main() { int *x[2]; int **y = &x[1]; return (y - x); } $ llvm-gcc -O3 -c test.c

...ptimizers. I think my case is stated above among your answer. http://nondot.org/sabre/LLVMNotes/SizeOf-OffsetOf-VariableSizedStructs.txt There is a brief document about using getelmentptr trick above. And I was wondering something similar to this case. %Size = getelementptr %T* null, int 1 %SizeI = cast %T* %Size to uint I understood that for this case, getelementptr will be collapsed to a number during optimization. It is also explained in the brief document above. I didn't understood by the document at that time. OK. Thank you very much. I understood very well. Sincerely Journeyer...

...t gmail.com> wrote: > > I'm trying to work out the size of a struct so that I can pass this to the > 'llvm.memcpy' intrinsic. It's easy to find out how I'm supposed to do this, > as I keep seeing the following: > > %Size = getelementptr %T* null, int 1 > %SizeI = cast %T* %Size to uint > > But I'm unsure how I actually do this in the C++ API. Is the 'null' here a > llvm::ConstantPointerNull? Any help here would be much appreciated. Try llvm::Constant::getNullValue(). > Additionally, I was wondering whether I can use this method t...

Chris Lattner wrote: > Check out http://nondot.org/sabre/LLVMNotes > > %Size = getelementptr %T* null, int 1 %SizeI = cast %T* %Size to uint How incredibly cunning. :-) Thanks for that. Next stupid question. I've put together a simple coroutine/fibre style threading system on top of the Linux setcontext/getcontext stuff, which surprisingly enough seems to work *almost* perfectly under the JITted envir...

Hi Journeyer, > I've got a question about getelementptr. > > I've been told that getelementptr is evaluated in compile-time NOT in run-time. this is impossible if the arguments are not constants. If they are constant, then the optimizers will turn a getelementptr instruction into a getelementptr constant expression (http://llvm.org/docs/LangRef.html#constant-expressions). Even

...model-checker-specific intrinsics so I can track memory modifications > efficiently, but just having the address isn't enough, I really need > the > size too. Or are reads and writes always guaranteed to be simple > types, > so the bit width (as given by the Type::getPrimitiveSizeInBits() > member > function) divided by 8 and rounded up if necessary is enough? (The > latter works well for me too, I just don't want to mess myself up by > making assumptions). > > As usual, thank you in advance. > > Sarah > _____________________________________...

Hello List, I've got a question about getelementptr. I've been told that getelementptr is evaluated in compile-time NOT in run-time. So I tested it with clang web compiler below. http://llvm.org/demo/index.cgi But with LTO nor Standard, neither one optimize getelementptr out. Does getelementptr get evaluated in compile-time? Or doesn't it get executed in run-time? (I believed so.

...store instructions into model-checker-specific intrinsics so I can track memory modifications efficiently, but just having the address isn't enough, I really need the size too. Or are reads and writes always guaranteed to be simple types, so the bit width (as given by the Type::getPrimitiveSizeInBits() member function) divided by 8 and rounded up if necessary is enough? (The latter works well for me too, I just don't want to mess myself up by making assumptions). As usual, thank you in advance. Sarah