[LLVMdev] How could I hide the visible string?

[Zhang Qiuyu]

Hi,

Is there a way to modify the string such as char a or char b?  Could I use the way like "Replace an instruction with another Value" in Programm Manual? In fact, what I am interested in is string with visible expression, not all string, and I am trying to hide the orignal string by using simple way like XOR.. 

Is there a way to reorder the basic blocks? 

Thanks.

Qiuyu

C Source code:

#include <stdio.h>
#include <stdlib.h>

char a[20]="global string test\n";

int main( int argc , char *argv[]){

  char b[20]= "Internal string test";

  printf("Global %s \n",a);
  printf("Internal %s\n",b);

}


IR code :

target endian = little
target pointersize = 32
 %struct..TorRec = type { int, void ()* }
 %struct.TorRec = type { int, void ()* }
%a = internal global [20 x sbyte] c"global string test\0A\00"  ; <[20 x sbyte]*> [#uses=1]
%.ctor_1 = internal global [20 x sbyte] c"Internal string test"  ; <[20 x sbyte]*> [#uses=1]
%.str_1 = internal constant [12 x sbyte] c"Global %s \0A\00"  ; <[12 x sbyte]*> [#uses=1]
%.str_2 = internal constant [13 x sbyte] c"Internal %s\0A\00"  ; <[13 x sbyte]*> [#uses=1]
%Initialized.0__ = internal global bool false  ; <bool*> [#uses=2]

implementation   ; Functions:

declare int %printf(sbyte*, ...)

int %main(int %argc, sbyte** %argv) {
entry:
 %b = alloca [20 x sbyte]  ; <[20 x sbyte]*> [#uses=1]
 %tmp.1.i = load bool* %Initialized.0__  ; <bool> [#uses=1]
 br bool %tmp.1.i, label %__main.entry, label %endif.0.i

endif.0.i:  ; preds = %entry
 store bool true, bool* %Initialized.0__
 br label %__main.entry

__main.entry:  ; preds = %entry, %endif.0.i
 %tmp.0 = getelementptr [20 x sbyte]* %b, uint 0, uint 0  ; <sbyte*> [#uses=2]
 call void %llvm.memcpy( sbyte* %tmp.0, sbyte* getelementptr ([20 x sbyte]*  %.ctor_1, long 0, long 0), uint 20, uint 1 )
 %tmp.3 = call int (sbyte*, ...)* %printf( sbyte* getelementptr ([12 x sbyte]*  %.str_1, long 0, long 0), sbyte* getelementptr ([20 x sbyte]*  %a, long 0, long 0) )  ; <int> [#uses=0]
 %tmp.6 = call int (sbyte*, ...)* %printf( sbyte* getelementptr ([13 x sbyte]*  %.str_2, long 0, long 0), sbyte* %tmp.0 )  ; <int> [#uses=0]
 ret int 0
}

declare void %llvm.memcpy(sbyte*, sbyte*, uint, uint)

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