[LLVMdev] How to extract loop body into a new function?

[Devang Patel]

Try ExtractCodeRegion or walk loop body and extract each basic block  
using ExtractBasicBlock.
-
Devang
On Dec 6, 2008, at 8:00 PM, Shah, Mrunal J wrote:

> False Alarm!!
>
> Still don't know how to do it!
>
> I am trying to write a transformation pass to extract a loop body  
> into a function.
> For example:
> The Loop in question is:
>  for (i2 = 0; i2 < LOOP_SIZE; i2++) {
>      A[B[i2]] =  2 * B[i2];
>  }
>
> The IR for which is:
> bb13:           ; preds = %bb13, %bb
>        %i2.0.reg2mem.0 = phi i32 [ 0, %bb ], [ %indvar.next62,  
> %bb13 ]         ; <i32> [#uses=2]
>        %tmp15 = getelementptr [25 x i32]* %B, i32 0, i32  
> %i2.0.reg2mem.0               ; <i32*> [#uses=1]
>        %tmp16 = load i32* %tmp15, align 4              ; <i32>  
> [#uses=2]
>        %tmp20 = shl i32 %tmp16, 1              ; <i32> [#uses=1]
>        %tmp21 = getelementptr [25 x i32]* %A, i32 0, i32  
> %tmp16                ; <i32*> [#uses=1]
>        store i32 %tmp20, i32* %tmp21, align 4
>        %indvar.next62 = add i32 %i2.0.reg2mem.0, 1             ;  
> <i32> [#uses=2]
>        %exitcond63 = icmp eq i32 %indvar.next62, 25            ;  
> <i1> [#uses=1]
>        br i1 %exitcond63, label %bb30, label %bb13
>
> I want to be able to extract:
>      A[B[i2]] =  2 * B[i2];
> into a function
>
> myfunc() {
>      A[B[i2]] =  2 * B[i2];
> }
>
> How can I do this?
>
> Any hints??
>
> Thanks,
> Mrunal
>
> ----- Original Message -----
> From: "Mrunal J Shah" <mrunal.shah at gatech.edu>
> To: "LLVM Developers Mailing List" <llvmdev at cs.uiuc.edu>
> Sent: Saturday, December 6, 2008 8:46:00 PM GMT -05:00 US/Canada  
> Eastern
> Subject: Re: [LLVMdev] How to extract loop body into a new function?
>
> Sorry!
> It worked with ExtractBasicBlock()
>
> ----- Original Message -----
> From: "Mrunal J Shah" <mrunal.shah at gatech.edu>
> To: "llvmdev" <llvmdev at cs.uiuc.edu>
> Sent: Saturday, December 6, 2008 8:30:33 PM GMT -05:00 US/Canada  
> Eastern
> Subject: [LLVMdev] How to extract loop body into a new function?
>
> Hi All,
>
> I am having trouble extracting loop body into a new function. The  
> ExtractLoop() or ExtractBasicBlock() extracts the entire loop along  
> with the header into a new function. All I want is to extract the  
> body of the loop into a new function(without the header).
> Is this possible?
>
> Thanks,
> Mrunal
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-
Devang