[LLVMdev] problem with loopinfo

[Chris Lattner]

On Thu, 15 Jun 2006, Wei Jiang wrote:
> I did run the indvars pass, but it seemed that it didn't work.

Then you'll have to trace through and find out why it's failing...

-Chris

> ----- Original Message ----- From: "Chris Lattner" <sabre at nondot.org>
> To: "LLVM Developers Mailing List" <llvmdev at cs.uiuc.edu>
> Sent: Thursday, June 15, 2006 3:35 PM
> Subject: Re: [LLVMdev] problem with loopinfo
>
>
>> On Thu, 15 Jun 2006, Wei Jiang wrote:
>>> hi,
>>>    The loopinfo pass failed to recognize the Tripcount of a simple program 
>>> constructed by me, can you help me to figure out why this happened? 
>>> Thanks.
>>>    The C program and corresponding .ll files are shown below. I used 
>>> llvm1.7 to develop my own pass, and want to use the loop information.
>> 
>> What passes are you running before your pass?  trip count information is 
>> generally only available after the "indvars" pass runs.
>> 
>> -Chris
>> 
>>> Test.c:
>>> #include "stdio.h"
>>> #define N 40
>>> void func1() {
>>>  int a[N];
>>>  int i,j;
>>>  for (i=0; i<N; i++) {
>>>      if (i==0)
>>>        a[i] = i*N;
>>>      else
>>>        a[i] = i*i;
>>>  }
>>> }
>>> 
>>> Test.ll:
>>> void %func1() {
>>> entry:
>>>        %a = alloca [40 x int]          ; <[40 x int]*> [#uses=1]
>>>        br label %no_exit
>>> 
>>> no_exit:                ; preds = %else, %then, %entry
>>>        %i.0.0 = phi int [ 0, %entry ], [ %inc9, %then ], [ %inc, %else ] ; 
>>> <int> [#uses=7]
>>>        %tmp.4 = seteq int %i.0.0, 0            ; <bool> [#uses=1]
>>>        %tmp.7 = getelementptr [40 x int]* %a, int 0, int %i.0.0 ; <int*> 
>>> [#uses=2]
>>>        br bool %tmp.4, label %then, label %else
>>> 
>>> then:           ; preds = %no_exit
>>>        %tmp.9 = mul int %i.0.0, 40             ; <int> [#uses=1]
>>>        store int %tmp.9, int* %tmp.7
>>>        %inc9 = add int %i.0.0, 1               ; <int> [#uses=2]
>>>        %tmp.112 = setlt int %inc9, 40          ; <bool> [#uses=1]
>>>        br bool %tmp.112, label %no_exit, label %return
>>> 
>>> else:           ; preds = %no_exit
>>>        %tmp.14 = mul int %i.0.0, %i.0.0                ; <int> [#uses=1]
>>>        store int %tmp.14, int* %tmp.7
>>>        %inc = add int %i.0.0, 1                ; <int> [#uses=2]
>>>        %tmp.1 = setlt int %inc, 40             ; <bool> [#uses=1]
>>>        br bool %tmp.1, label %no_exit, label %return
>>> 
>>> return:         ; preds = %else, %then
>>>        ret void
>>> }
>>> 
>> 
>> -Chris
>> 
>> -- 
>> http://nondot.org/sabre/
>> http://llvm.org/
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>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
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>> 
>
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-Chris

-- 
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