llvm dev - Dec 2012 - [LLVMdev] issue with profiling in LLVM 3.1

Hi,

I am using the profiling feature of LLVM 3.1. Mostly, it works well, but 
seems to be wrong in a few cases. For example, I have found that the 
number of times a function executed is reported as less than the number 
of times that the basic block calling this function executed (the 
difference was about 25x!). I am copying out the exact functions below. 
The relevant parts are in bold font:

*------------*
*SOURCE :
------------*

//accumulate error at a given edge sample point (round to nearest 
integral point)
*inline void SampleEdgePoint(float xf, float yf, const FlexImage8u 
&EdgeMap, int &error, int &samplePoints)
{
         int x = int(xf + 0.5f), y = int(yf + 0.5f);
         if((x >= 0) && (x < EdgeMap.Width()) && (y >=
0) && (y <
EdgeMap.Height())) //check image bounds
         {       int e = 255 - 
EdgeMap(x,y);
//get value from image map and compute difference
                 error += (e * 
e);
//sum squared error values
                 
samplePoints++;
//count points sampled
         }
}*

//Generate Samples for points along the non-joint edges of the cylinder
*void ImageMeasurements::EdgeError(const ProjectedCylinder &ProjCyl, 
const FlexImage8u &EdgeMap, float &error, int &samplePoints)*
{
         int ErrorSSD = 0;
         const Point &p1 = ProjCyl.mPts[0];
         Point 
s1;
//get direction vector of side 1 of the 2D cylinder projection
         s1.Set(ProjCyl.mPts[1].x - p1.x, ProjCyl.mPts[1].y - p1.y);
         int n1 = max((int)(mag(s1) / mStep + 0.5), 
4);                                                  //compute number of 
points sampled (sample at least 4)
         float d1 = 1.0f / 
(float)n1++;
//get fraction of side length per sample

         const Point &p2 = ProjCyl.mPts[2];
         Point 
s2;
//repeat for side 2 of cylinder
         s2.Set(ProjCyl.mPts[3].x - p2.x, ProjCyl.mPts[3].y - p2.y);
         int n2 = max((int)(mag(s2) / mStep + 0.5), 4);
         float d2 = 1.0f / (float)n2++;

         float delta = 0;
         for(int i = 0; i < n1; 
i++)
//generate sample points along each side of cylinder projection
         {       float x = p1.x + delta * s1.x;
                 float y = p1.y + delta * s1.y;
*SampleEdgePoint(x, y, EdgeMap, ErrorSSD, samplePoints); 
*                       //accumulate error at computed edge points on side 1
                 delta += d1;
         }
         delta = 0;
         for(int i = 0; i < n2; i++)
         {       float x = p2.x + delta * s2.x;
                 float y = p2.y + delta * s2.y;
*SampleEdgePoint(x, y, EdgeMap, ErrorSSD, 
samplePoints);*                         //accumulate error at comptued 
edge points on side 2
                 delta += d2;
         }
         error += (float)ErrorSSD / (255.0f * 255.0f);
}

*---------------------------*
*Call instructions in IR:
---------------------------

invoke void @_Z15SampleEdgePointffRK9FlexImageIhLi1EERiS3_(float %109, 
float %110, %class.FlexImage* %111, i32* %ErrorSSD, i32* %112)
           to label %113 unwind label %124

invoke void @_Z15SampleEdgePointffRK9FlexImageIhLi1EERiS3_(float %150, 
float %151, %class.FlexImage* %152, i32* %ErrorSSD, i32* %153)
           to label %154 unwind label %124*


Thanks.
-Apala










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