Hi,
I have the following code, the lines preceded by `>` being added at runtime
(the snipped was also printed at runtime)
define i32 @myfunc(i32 %pi) {
entry:
%pi_addr = alloca i32 ; <i32*> [#uses=3]
%retval = alloca i32 ; <i32*> [#uses=2]
%tmp = alloca i32 ; <i32*>
[#uses=2]> %ptr32 = alloca i32 ; <i32*> [#uses=2]
%"alloca point" = bitcast i32 0 to i32 ; <i32>
[#uses=0]
> store i32 %pi, i32* %ptr32
> %ptr8 = bitcast i32* %ptr32 to i8* ; <i8*>
[#uses=1]
> call void @roc( i8* %ptr8 )
store i32 %pi, i32* %pi_addr
%pi_addr1 = bitcast i32* %pi_addr to i8* ; <i8*>
[#uses=1]
call void @roc( i8* %pi_addr1 )
...
void roc(void*) is a function that only prints its argument as an integer.
I was expecting for the program to print the same thing twice (the address
of the myfunc argument) because the code added at runtime looks to me
identical with the code that was compiled (3 lines each).
However, that was not the case; what I got was:
147156320
147117168
What am I missing?
Thanks,
Paul
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Paul Martin wrote:> Hi, > I have the following code, the lines preceded by `>` being added at > runtime (the snipped was also printed at runtime) > > define i32 @myfunc(i32 %pi) { > entry: > %pi_addr = alloca i32 ; <i32*> [#uses=3] > %retval = alloca i32 ; <i32*> [#uses=2] > %tmp = alloca i32 ; <i32*> [#uses=2] > > %ptr32 = alloca i32 ; <i32*> [#uses=2] > %"alloca point" = bitcast i32 0 to i32 ; <i32> [#uses=0] > > > store i32 %pi, i32* %ptr32 > > %ptr8 = bitcast i32* %ptr32 to i8* ; <i8*> [#uses=1] > > call void @roc( i8* %ptr8 ) > > store i32 %pi, i32* %pi_addr > %pi_addr1 = bitcast i32* %pi_addr to i8* ; <i8*> > [#uses=1] > call void @roc( i8* %pi_addr1 ) > ... > > void roc(void*) is a function that only prints its argument as an integer.So it's printing the pointer.> I was expecting for the program to print the same thing twice (the > address of the myfunc argument) because the code added at runtime looks > to me identical with the code that was compiled (3 lines each). > However, that was not the case; what I got was: > > 147156320 > 147117168 > > What am I missing?Make roc() dereference the pointers it's given and print that instead. Nick
Nick, Thanks for the quick answer. Dereferencing the pointer does yield the same result in both cases but that's not what I want to do. I want to instrument the program dynamically and keep track of certain memory locations which is a problem if the same variable has different addresses for the static/dynamic code - as far I see this is what it's happening but I have no clue why. Paul On Sun, May 24, 2009 at 10:15 PM, Nick Lewycky <nicholas at mxc.ca> wrote:> Paul Martin wrote: > > Hi, > > I have the following code, the lines preceded by `>` being added at > > runtime (the snipped was also printed at runtime) > > > > define i32 @myfunc(i32 %pi) { > > entry: > > %pi_addr = alloca i32 ; <i32*> [#uses=3] > > %retval = alloca i32 ; <i32*> [#uses=2] > > %tmp = alloca i32 ; <i32*> [#uses=2] > > > %ptr32 = alloca i32 ; <i32*> [#uses=2] > > %"alloca point" = bitcast i32 0 to i32 ; <i32> [#uses=0] > > > > > store i32 %pi, i32* %ptr32 > > > %ptr8 = bitcast i32* %ptr32 to i8* ; <i8*> > [#uses=1] > > > call void @roc( i8* %ptr8 ) > > > > store i32 %pi, i32* %pi_addr > > %pi_addr1 = bitcast i32* %pi_addr to i8* ; <i8*> > > [#uses=1] > > call void @roc( i8* %pi_addr1 ) > > ... > > > > void roc(void*) is a function that only prints its argument as an > integer. > > So it's printing the pointer. > > > I was expecting for the program to print the same thing twice (the > > address of the myfunc argument) because the code added at runtime looks > > to me identical with the code that was compiled (3 lines each). > > However, that was not the case; what I got was: > > > > 147156320 > > 147117168 > > > > What am I missing? > > Make roc() dereference the pointers it's given and print that instead. > > Nick > > _______________________________________________ > LLVM Developers mailing list > LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20090524/3a4f7735/attachment.html>
Hi Paul,> I have the following code, the lines preceded by `>` being added at > runtime (the snipped was also printed at runtime) > > define i32 @myfunc(i32 %pi) { > entry: > %pi_addr = alloca i32 ; <i32*> [#uses=3] > %retval = alloca i32 ; <i32*> [#uses=2] > %tmp = alloca i32 ; <i32*> [#uses=2] > > %ptr32 = alloca i32 ; <i32*> [#uses=2] > %"alloca point" = bitcast i32 0 to i32 ; <i32> [#uses=0] > > > store i32 %pi, i32* %ptr32 > > %ptr8 = bitcast i32* %ptr32 to i8* ; <i8*> [#uses=1] > > call void @roc( i8* %ptr8 ) > > store i32 %pi, i32* %pi_addr > %pi_addr1 = bitcast i32* %pi_addr to i8* ; <i8*> > [#uses=1] > call void @roc( i8* %pi_addr1 ) > ... > > void roc(void*) is a function that only prints its argument as an integer. > > I was expecting for the program to print the same thing twice (the > address of the myfunc argument) because the code added at runtime looks > to me identical with the code that was compiled (3 lines each). > However, that was not the case; what I got was:%pi_addr and %ptr32 are two different automatic variables. You are printing their addresses and these are different. Maybe you meant to print the contents of the variables?> > 147156320 > 147117168Ciao, Duncan.