[LLVMdev] LLVM Optmizer

[Bill Wendling]

Hi Manoel,

More info is needed. What optimization level did you use when
compiling LLVM? What does the LLVM x86 assembly code look like? How is
this run? What are the times you're seeing? What is your system's
configuration?

-bw

On Tue, Jan 6, 2009 at 3:02 AM, Manoel Teixeira <manoel at fonetica.com.br> wrote:
>
>  The following C code :
> #include <stdio.h>
> #include <stdlib.h>
>
> int  TESTE2( int  parami , int paraml ,double  paramd  )
> {
>  int varx=0,vary;
>  int nI =0;
>  //varx= parami;
>    if( parami > 0  )
>        {
>   varx = parami;
>   vary = varx + 1;
>        }
>  else
>  {
>   varx = vary + 1;
>   vary = paraml;
>  }
> varx = varx + parami + paraml;
>  for( nI = 1 ;   nI <=  paraml; nI++)
>  {
>    varx =  varx + parami + 1 ;
>        vary =  varx + nI;
>  }
>  vary = varx + 5;
>  varx = vary + paraml;
>
> return varx ;
> }
>
> Generates the IR :
> ; ModuleID = '/tmp/webcompile/_9908_0.bc'
> target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32"
> target triple = "i386-pc-linux-gnu"
>
> define i32 @TESTE2(i32 %parami, i32 %paraml, double %paramd) nounwind readnone {
> entry:
>        %0 = shl i32 %parami, 1         ; <i32> [#uses=1]
>        %varx.110 = add i32 %0, %paraml         ; <i32> [#uses=2]
>        %1 = icmp slt i32 %paraml, 1            ; <i1> [#uses=1]
>        br i1 %1, label %bb5, label %bb3
>
> bb3:            ; preds = %bb3, %entry
>        %indvar = phi i32 [ %indvar.next, %bb3 ], [ 0, %entry ]         ; <i32> [#uses=3]
>        %2 = add i32 %indvar, 2         ; <i32> [#uses=1]
>        %3 = icmp sgt i32 %2, %paraml           ; <i1> [#uses=1]
>        %indvar.next = add i32 %indvar, 1               ; <i32> [#uses=1]
>        br i1 %3, label %bb5.loopexit, label %bb3
>
> bb5.loopexit:           ; preds = %bb3
>        %tmp14 = add i32 %parami, 1             ; <i32> [#uses=1]
>        %tmp15 = mul i32 %indvar, %tmp14                ; <i32> [#uses=1]
>        %varx.111 = add i32 %tmp15, %varx.110           ; <i32> [#uses=1]
>        %4 = add i32 %varx.111, %parami         ; <i32> [#uses=1]
>        %phitmp = add i32 %4, 1         ; <i32> [#uses=1]
>        br label %bb5
>
> bb5:            ; preds = %bb5.loopexit, %entry
>        %varx.1.lcssa = phi i32 [ %varx.110, %entry ], [ %phitmp, %bb5.loopexit ]               ; <i32> [#uses=1]
>        %5 = add i32 %paraml, 5         ; <i32> [#uses=1]
>        %6 = add i32 %5, %varx.1.lcssa          ; <i32> [#uses=1]
>        ret i32 %6
> }
>
>
> While the MSVC generates the assemble :
> PUBLIC  _TESTE
> ; Function compile flags: /Ogtpy
> ; File c:\msys\1.0\home\mteixeira\testeadvpl.c
> ;       COMDAT _TESTE
> _TEXT   SEGMENT
> _parami$ = 8                                            ; size = 4
> _paraml$ = 12                                           ; size = 4
> _paramd$ = 16                                           ; size = 8
> _TESTE  PROC                                            ; COMDAT
>
> ; 6    :   int varx=0,vary;
> ; 7    :   int nI =0;
> ; 8    :   //varx= parami;
> ; 9    :     if( parami > 0  )
>
>        mov     ecx, DWORD PTR _parami$[esp-4]
>
> ; 10   :        {
> ; 11   :    varx = parami;
> ; 12   :    vary = 0;
> ; 13   :        }
> ; 14   :   else
> ; 15   :   {
> ; 16   :    varx = 0;
> ; 17   :    vary = paraml;
> ; 18   :   }
> ; 19   :   for( nI = 1 ;   nI <=  paraml; nI++)
>
>        mov     edx, DWORD PTR _paraml$[esp-4]
>        xor     eax, eax
>        test    ecx, ecx
>        setle   al
>        sub     eax, 1
>        and     eax, ecx
>        cmp     edx, 1
>        jl      SHORT $LN3 at TESTE
>        add     ecx, 1
>        imul    ecx, edx
>        add     eax, ecx
> $LN3 at TESTE:
>
> ; 20   :   {
> ; 21   :     varx =  varx + parami + 1 ;
> ; 22   :        vary =  varx + nI;
> ; 23   :   }
> ; 24   :
> ; 25   : return varx ;
> ; 26   : }
>
>        ret     0
> _TESTE  ENDP
> _TEXT   ENDS
>
>  Running the same code, the objetc generated with MSVC is 600 times faster than that generate with the LLVM compiler
>  Is threre any way to get the same optimzation with the LLVM?
>
>
> Manoel Teixeira
>
>
>
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