[LLVMdev] LLVM Optmizer

[Manoel Teixeira]

 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