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On Jul 24, 2015, at 10:46 AM, Zhoulai <zell08v@gmail.com> wrote:

Hi,

Are there some built-in LLVM transformation pass, or written library code that transforms LLVM::SwitchInst into if-condition statements (LLVM:: BranchInst)?

There is a -lowerswitch pass that rewrites switch instructions with a sequence of branches.

http://llvm.org/docs/Passes.html#lowerswitch-lower-switchinsts-to-branches

thanks,

chen

The purpose of the transformation is that we have a legacy program analyzer that includes an LLVM pass manipulating if-condition statements. Statements of LLVM::SwithchInst should have been handled in the same manner but was not done. Thus to transform these SwitchInst to if-condition looks a viable alternative for us.

To illustrate, I give a simple C snippet with 'switch' and the expected transformation.
----------------------------------------
Original program:

char grade;
...
switch(grade)
{
case 'A' :
printf("Excellent!\\n" );
break;
case 'B' :
printf("Well done\\n" );
break;

default :
printf("Invalid grade\\n" );
}

may be transformed to something like

if (grad=='A')
printf("Excellent!\\n" );
else if (grad=='B')
printf("Well done\\n" );
else
printf("Invalid grade\\n" );
-------------------------------------------------

Are you aware of such a transformation pass ? Thanks.
Zhoulai

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